British Journal of Psychiatry (1986), 149, 698—709

CAMDEXA Standardised Instrument for the Diagnosis of Mental Disorder

in the Elderly with Special Reference to the Early Detection of Dementia

M. ROTH, E. TYM, C. Q. MOUNTJOY, F. A. HUPPERT, H. HENDRIE, S. VERMA and R. GODDARD

A new interview schedule for the diagnosis and measurement of dementia in the elderlyis described. The schedule named the Cambridge Mental Disorders of the ElderlyExamination (CAMDEX), consists of three main sections: (1) A structured clinical interviewwith the patient to obtain systematic information about the present state, past historyand family history; (2) a range of objective cognitive tests which constitute a minineuropsychological battery; (3) a structured interview with a relative or other informantto obtain independent information about the respondent's present state, past history andfamily history. The CAMDEX is acceptable to patients, has a high inter-rater reliabilityand the cognitive section has been shown to have high sensitivity and specificity.

Introduction

Attempts have been made in the past to assess andcharacterise patients suffering from dementia in lateand middle life. They have aimed at resolving threerelated, but relatively distinct, problems:

(1) To diagnose dements reliably either by the useof operational criteria such as those set downin DSM-lII (American Psychiatric Association1980) or by using standardised methods ofinterview and examination such as the PresentState Examination (PSE) of Wing et a!(1974)or its derivatives.

(2) To develop valid and reliable measures of theseverity and extent of cognitive impairmentwhich constitutes a central feature in establishedcases of dementia.

(3) To devise reliable means of rating behaviourand adaptation in everyday life that are asobjective and precise as the situation permitsand independent of clinical diagnosis orseverity of dementia as judged from performance on standardised tests.

As a result of these enquiries, a number of scalesuseful for certain specific purposes have beendeveloped. For example, standardised diagnosticinterviews such as the Psychogeriatric AssessmentSchedule (PAS) of Bergmann et al(1975) are capableof separating groups of patients into ‘¿�demented'and‘¿�non-demented'or ‘¿�functional'groups. This makesthem valuable for certain kinds of scientific enquiry:for example, clinical trials or epidemiological studies

in the community to provide a basis for social andhealth care planning. A large number of cognitivetests have come into existence which are of two broadtypes. Mental state examinations are capable ofdifferentiating between the presence or absence ofsignificant cognitive impairment while tests whichderive from the psychometric tradition such as theKendrick Battery (Kendrick, 1972; Kendrick &Moyes, 1979) permit an assessment of severity ofcognitive impairment. There are also many usefulbehaviour rating scales which can detect problemsin the activities of daily living. One of these scales,the widely used Dementia Scale of Blessed eta! (1968)shows a good correlation with Alzheimer neuropathology, while the rating scale of Roberts & Caird(1976) has been found to correlate with computedtomography (CT) scans.

However, one source of difficulty and confusionhas been the failure to differentiate between the typeof information which each of these three approachescan validly yield. In consequence, a scale or interviewdeveloped to answer one type of question has beeninappropriately used to answer another. For example,behavioural scales alone have been employed asmeasures of dementia or the results of cognitive testshave been used to establish a diagnosis. Suchmisconceptions are liable to introduce error andconfusion, into research endeavours and clinicalpractice alike.

We believe that the three approaches tocharacterising the demented patient arecomplementary. All three are required to obtain a

698

699DIAGNOSISOF MENTAL DISORDER BY CAMDEX

complete picture of the disorder. The centralobjective of the endeavour to be described in thispaper was to incorporate these different kinds ofmeasure within a single compact, integratedinstrument that has an acceptable measure ofreliability and validity.

Developments in the diagnosis of dementia

Although operational criteria for the diagnosis ofdementia such as those provided in DSM-III haveimproved stringency in diagnostic practice, they aresomewhat arbitrary. Moreover, these criteria do notserve to identify mild dementia which presents aproblem of central importance in this field(Henderson & Huppert, 1984).

There is more promise in the structured and semistructured interview schedule from which diagnosisof organic mental disorder can be derived. The twobest known schedules are the Present StateExamination (PSE) of Wing et al (1974) and theDiagnostic Interview Schedule (DIS) of Robins et al(1981). However, neither of these instrumentsprovide sufficient information regarding the historyof onset and the character and progression ofcognitive impairment.

The Geriatric Mental State Examination (GMS)of Copeland et a! (1976) which is largely derived fromthe PSE and uses the same hierarchical approach tothe problem of diagnosis, incorporates more tests ofcognitive function. It has been used in the influentialUS-UK Diagnostic Project for comparing mentaldisorder in the elderly in New York and London andhas now been incorporated, with some modification,into the Comprehensive Assessment and ReferralEvaluation (CARE) of Gurland et a! (1977). Itdifferentiates between six principal diagnostic categories of old age mental disorder. They are: affectivedisorders, schizophrenia/paranoid states, organicpsychoses, alcoholism, neuroses and personalitydisorders, and other diagnoses. And in two smallstudies of inter-rater reliability (Copeland et al,1976), the diagnostic agreement was of the order of85°loon a sample of 20 and 73°loon a sample of 22patients.

These scales represent an advance in that theystandardise the examination of the present mentalstate and render the findings relating to the presentstate more objective and replicable. However, theentire psychiatric examination required to make adiagnosis has not been standardised.

This is of particular importance in the characterisation and measurement of dementia. The relevantdata cannot be extracted from standardised examinations formed on the present mental state alone. Such

findings can lead to error if they are not combinedwith data relating to the development of the disorder.Information regarding adaptation during development and basic personality traits and observations onthe behaviour of the patient over a period of timeare also needed to determine the extent of his premorbid traits and competence in negotiating everydaytasks. For such information, the judgments of arelative or friend or observations conducted over aperiod in hospital, are indispensable. Such behaviourwill sometimes be deranged and disorganised beforeevidence suggestive of dementia comes to light duringa structured interview. To cite an example, in thecourse of a cross-sectional examination, a differentialdiagnosis between dementia and states of subacuteclouding of consciousness can be difficult orimpossible. Yet given a few items of informationregarding the history and development of thecondition and the background of the individual, thediagnosis rarely presents difficulties.

Differential diagnosis

Both in respect of therapy and scientificinvestigation, the failure to differentiate betweenforms of dementia attributable to different aetiological processes would serve to obscure importantfindings. Multi-infarct dementia requires to bedifferentiated from Alzheimer's Disease and theIschaemia Score (Hachinski et a!, 1975) has madea start in relation to this. Means of refining theHachinski score have been suggested (Roth, 1981)and they have been incorporated in the interviewdescribed here. Again, clouded and delirious statesneed to be separated from the dementias. Doubtsabout diagnosis can be resolved by informationrelating to the development of the disorder, theprevious medical history and evidence regarding drugand alcohol abuse. The record of previous psychiatricillness and family history can help in the differentiation of pseudo-dementia from true dementia. Thefamily record can also assist in the differentiationof Alzheimer's disease of ‘¿�early'and ‘¿�late'onset; anexcessive prevalence of dementia in first degreerelatives has been found more commonly in ‘¿�early'cases (Heston, 1984).

Measurement of the rangeand severity of cognitive Impairment

A scale for the objective assessment of cognitivefunction is an essential component of any systematicschedule for the diagnosis and precise delineation ofdementia. Subjective complaints of poor memoryand word finding difficulty have been shown to be

700 ROTH ET AL

more influenced by depressed mood than byobjective evidence of cognitive impairment (e.g.Kahn et a!, 1960). The cognitive section of the GMSand the CARE have therefore to be interpreted withcaution, since they contain a large number of selfreport items. Nor are standard mental statusquestionnaires, of which there are a large number,adequate for this purpose. Although they employobjective tests, they are usually concerned only withmemory and orientation and designed for use witha markedly impaired population. A cognitivefunction test must sample a broad enough range offunctions to meet diagnostic criteria for dementia:DSM-lll for example, requires the demonstration ofa generalised loss of cognitive functions includinglanguage, praxis, perception, abstract thinking andconstructional ability as well as memory. Both theolder and some of the more recent schedules fail tomeet these requirements.

The Mini Mental State Examination (MMSE) ofFolstein et a! (1975) appears to be the best briefobjective cognitive test currently in use as part of adiagnostic schedule (it has been incorporated into theDIS), but even the MMSE fails to assess perceptualability and abstract thinking, and permits only arudimentary assessment of most other functions. Forthis reason, we have developed our own cognitivetest as part of the diagnostic schedule. However,given the popularity of the MMSE and its use in theinfluential survey of elderly community residents

currently being undertaken by the National Instituteof Aging in the USA, we included the Mini MentalState Examination in our cognitive section to enabledirect comparisons with the results of otherinvestigators.

A further requirement for a research diagnostictool, is the reliable grading of severity of dementia.A number of rating scales have been developed inrecent years notably the Clinical Dementia Rating(CDR) of Hughes et a! (1982) and the GlobalDeterioration Scale (GDS) of Reisberg et a! (1982).The CDR rates dementia along a five-point scale(none, questionable, mild, moderate, severe) on thebasis of the person's performance in six areas of dailyliving: memory, orientation, judgement and problemsolving, community affairs, home and hobbies, andpersonal care. The criteria are not easy to apply inpractice, but questions also arise regarding theirvalidity. Patients may receive the same rating (e.g.CDR 1 or mild dementia) whether or not they haveadditional difficulty with language or praxis. Yet ina 12-month follow-up study, a poorer prognosis hasbeen reported for patients who had such difficultyat the initial assessment. Patients who progressed tomoderate (CDR 2) or severe dementia (CDR 3)

performed significantly worse when originallyassessed on all tests of language and praxis as wellas on most memory tests (Berg eta!, 1983). Findingssuch as these make it imperative that all areas ofcognition should be taken into account when arrivingat a severity rating. The Global Deterioration Scale(GDS) of Reisberg el a! (1982) grades cognitiveimpairment along a seven-point scale, but the criteriarely very heavily on the severity of memory disorder.While we acknowledge that grading the severity ofdementia is not an easy task, we propose to showthat a clinical assessment of severity based on a rangeof cognitive tasks and activities of daily living canbe made in a reliable way.

In its present form, the CAMDEX focuses on thediagnosis of dementia, with particular reference toits mild forms and to the identification of specifictypes of dementia. This task requires the differentiation of dementia from non-dementing conditionswhich may masquerade as dementia. Hence itemsrelevant to other diagnoses must be included. Suchitems, particularly those relating to depression andparanoid states, are also needed to complete theclinical picture in dementia and are of therapeuticimportance. At a later stage when an adequate bodyof CAMDEX data for patients with a wide range ofpsychiatric diagnoses has been collected it may bepossible to broaden the CAMDEX into a comprehensive diagnostic instrument for psychiatricdisorders of the elderly.

Objectives in the developmentof the present schedule

We have attempted in the development of theschedule which we have called the Cambridge MentalDisorders of the Elderly Examination (CAMDEX),to remedy the gaps in the existing standardisedinterviews and scales of measurement. We understand that since we began work on this projectadditional sections are now being added to the GMSto provide this information (Copeland, personalcommunication).

In developing the CAMDEX we have sought tocreate a diagnostic schedule with the following mainingredients.

(1) A structured psychiatric interview with therespondent incorporating questions regardingthe present mental disorder and the pasthistory and family history.

(2) The objective evaluation of a broad range ofcognitive functions.

(3) A standardised schedule for recording observations of the present mental state togetherwith appearance and demeanor.

701DIAGNOSIS OF MENTAL DISORDER BY CAMDEX

(4) A structured interview with a relative or otherinformant able to provide independentinformation regarding the respondent'spresent state, any changes in personality andactivities of daily living, past history, andfamily history.

(5) A brief physical examination includingneurological examination.

(6) A record of a range of laboratory findings andpresent medication where applicable.

The CAMDEX schedule

In its present form this schedule comprises a numberof sections which are outlined below. It starts witha sheet on which basic demographic data arerecorded.

Section A

This section covers items of enquiry regarding thepatient's present physical and mental state and inparticular seeks symptoms relating to organicpsychoses, depression and functional paranoidpsychoses. Enquiries regarding past history andfamily history are also made. The questions posedin the final part of this section are prompted by thepreliminary evidence suggesting a relationship inAlzheimer's disease on the one hand, and Down'ssyndrome and leukaemia on the other (Heston &Mastri, 1977). The section starts with three simplequestions; the patient's name, age and date of birth.If the patient fails to provide satisfactory answersto two out of three questions the interviewerabandons Section A and moves on to Section B.

Section B

This consists of the cognitive examination. The 19items which comprise the widely used Mini MentalState Examination (MMSE) of Folstein et a! (1975)are incorporated into this section. However, anumber of additional items have been included tocompensate for weaknesses in the MMSE. First, theMMSE does not sample certain cognitive functionse.g. abstract thinking and perception, which arerelevant to diagnosis and are included in DSM-IIIoperational criteria for primary degenerative dementia.Second, many functions are assessed by the MMSEin insufficient detail. For example, memory isassessed only by the repetition and recall of threewords; we have added items covering remote andrecent memory and the recall and recognition of newinformation. (For full details of the cognitiveexamination see Huppert et a!, 1985.) Thus the

cognitive section of the CAMDEX provides a widercoverage of cognitive functions than the MMSE, aswell as more information about most functions. Thetest assesses orientation, language, memory, praxis,attention, abstract thinking, perception andcalculation. Parts of each interview have beenrecorded so that various aspects of spontaneousspeech and the content of language can be systematically assessed later.

Section C

This consists of the interviewer's observations on thepatient's appearance, behaviour, mood, speech,mental slowing, activity, insight, thought processesand level of consciousness, and any bizarrebehaviour. The section is completed at the end ofthe interview.

Section D

This comprises a simple physical examinationincluding blood pressure, superficial and tendonreflexes, gait, defects of hearing or sight, tremor andParkinsonian features to provide some of theinformation needed for differentiating between‘¿�primary'and ‘¿�secondary'dementias.

Section E

The results of laboratory and radiological investigations are recorded in this section. Blood count, B12and folate, urea and electrolytes, liver function tests,VDRL, skull X-ray and CT scan, are recordedwhenever available.

Section F

A record is set down of any medication currentlybeing taken by the patient, and a note of theapproximate period during which drugs have beentaken.

Section G

This provides for any additional items of informationobtained in the course of the interview. The purposeof this section is to amplify the picture of the patientalready obtained by the structured questions. Muchinformation in this section is spontaneously offeredand of interest on this account alone in addition tothe help it may afford to formulate a diagnosis atthe end of the interview, particularly in atypical anddifficult cases.

groupsInterviewer

diagnosisNormalsObserverdiagnosis

DementiaCloudingDepressionNormal

DementiaCloudingDepression9 122

1 412

702 ROTH ET AL

Section H

This comprises the structured interview with arelative, or a carer who knows the patient well. Anypersonality change, difficulty in functioning ineveryday life or indications of cognitive difficultynoticed by the carer are noted. Items which permitthe Newcastle Dementia Score (Blessed et a!, 1968)to be scored are incorporated in this section.Questions referable to the presence or absence ofdepressive or paranoid phenomenology are included.Family history and past history are investigated withthe aid of questions similar to those asked of thepatient.

At the end of the interview, the interviewer makesa psychiatric diagnosis based on all relevant andavailable information according to operationaldiagnostic criteria. Diagnoses are assigned to one of11 categories: normal, four categories of dementia(senile dementia of the Alzheimer type (SDAT),multi-infarct dementia (MID), mixed SDAT andMID; dementia secondary to other causes), twocategories of clouding or delirium (clouded state,clouded state with dementia), depression, anxiety orphobic disorder, paranoid or paraphrenic illness andother psychiatric disorder. Patients are also gradedfor severity of dementia and severity of depressioneach on a five-point scale.

Durationof administrationThe administration of the respondent's part of theinterview can be completed in about 60 minutes. Theinformant's section takes about 20 minutes.

TABLE IInter-rater reliability of CAMDEX for major diagnostic

Method

The 40 patients participating in the study of inter-raterreliability were rated at the same time by two psychiatrists;one acting as interviewer for the whole interview and theother as observer. Both psychiatrists completed theCAMDEX independently. One psychiatrist (E.T.) waspresent at the interview of all patients and was theinterviewer in half the interviews. Three other psychiatrists(H. H., 5. V., R. 0.) took part in the reliability study. Twoof the four psychiatrists were trained in the UK and twoin the USA. For each patient the ratings of the twopsychiatrists were compared for all items and for eachsection of the CAMDEX. The purpose of the item analysiswas to identify the questions with a high rate ofdisagreement between interviewers so that the source of thedisagreement could be ascertained and the questionmodified or discarded from the next edition of the schedule.

The agreement between interviewers was measured bymeans of the phi (@)coefficient (Guilford & Fructer, 1981).Although@ can vary from —¿�1 to + 1, only under certainconditions can the coefficient be as extreme as either ofthese limits. It is only when the two means are identicalthat the coefficient equals 1. The degree of differencebetween means is reflected in the degree of reduction inthe value of the@ coefficient.

Test procedure Results

Subjects

Forty patients (33 female and 7 male) over theage of 65 were interviewed for the reliability study.The main diagnostic categories are given in Table I.A further 52 patients were interviewed (R.G.) sothat clinical diagnostic scales could be developedand the cognitive tests used on a larger population.There were 61 females and 31 males in all.They were recruited mainly from inpatients andoutpatients from the Department of GeriatricMedicine at Addenbrooke's Hospital, Cambridge,and the Department of Psychogeriatrics, FulbournHospital, Cambridge. The normal group consistedof both geriatric patients and community residents, chiefly from warden-controlled shelteredaccommodation.

Inter-rater reliability

Diagnostic agreement

There was good agreement between pairs of psychiatristsin the main diagnostic groupings (Table I). There wascomplete agreement on cases diagnosed by the intervieweras normal or demented. One of the five cases diagnosedby the interviewer as clouded was classed as demented bythe observer, while of the four cases diagnosed by theinterviewer as depressed, the observer agreed on two, butclassed one as normal and one as demented.

The 4 coefficient for diagnostic agreement was reducedto 0.63 when dementia was subdivided into four diagnosticcategories: SDAT, MID, mixed SDAT and MID anddementia secondary to other causes. There was completeagreement between raters on the ten cases diagnosed by theinterviewer as SDAT and one case of secondary dementia.Two of the eight cases diagnosed as MID were classed as

PearsonCoefficientscorrelationsof(2

x 2 agreement!disagreementontotal

scoresforeachSectionindividual

items)sectionMedian

RangerPA

Interview with0.94 1.0—0.280.990.000patientB

Cognitiveexamination0.90

1.0—0.300.970.000C

Observations0.83 1.0—0.300.810.000HInterview with0.91 1.0—0.560.900.000informant

Normal (n=17)90.0(72—101)26.7(22—29)Demented(n=49)44.2(8—82)13.4(1—25)Clouded

(n=14)52.3(38—79)15.3(9—27)Depressed(n= 12)83.9(68—98)24.8(14—30)

703DIAGNOSISOF MENTAL DISORDER BY CAMDEX

normals, 26 with SDAT, 13with MID, seven mixed SDATand MID, three with dementia secondaryto other conditions, fiveclouded-delirious(hereaftercalledcloudedstate),nine clouded states superimposed on dementia, and 12depressed patients. For the three cases where interviewerand observer disagreed about the diagnosis, theinterviewer's diagnosis was used. There was no significantdifferencebetweendiagnosticgroups in respectof sex orageof the patients, exceptthat the depressedpatientsweresignificantly younger (71.9) than the normal (79.5), SDAT(79.3) and MID (80.1) groups.

Sensitivity and specificity

Fromthecognitivesection(SectionB)weobtaintwooverallmeasures of cognitive function: (a) total score on the MiniMental State Examination (MMSE) of Folstein et a! (1975)and (b) total score on The Cambridge CognitiveExamination (CAMCOG) which consists of 14 of the 19MMSE items plus 43 items covering additional aspects ofcognitivefunction. Maximumscoresare 30on the MMSEand 106 on the CAMCOG.

Table III shows the cognitivescores in the four majordiagnostic groups. The normal and depressed groups didnot differ significantlyfrom each other on either test butperformed markedly better than either the demented orcloudedgroups(P<0.001) whichdid not differ from eachother.

The sensitivity and specificity of the two tests fordetecting organic mental impairment have been calculated.For the MMSEa cut-off valueof 21/22 wasrecommendedfor those aged 60 or over (Anthony eta!, 1982). Using thiscut-off we obtain values of 96¾sensitivity and 80¾specificityfor our population.Thismeansthat 96¾of caseswith an MMSEscoreof 21 or lesshad a clinicaldiagnosisof organicmentaldisorder(dementiaor cloudedstate)while80¾of cases with an MMSE score of 22+ had beendiagnosed as normal or depressed. Conversely, 20'lo ofthosescoring22+ had a clinicaldiagnosisof organicmentaldisorder and hence were misclassifiedusing this cut-off.We found that the optimal cut-off for our sample, was23/24 which yielded 94¾sensitivity and 85°lospecificity.

Sensitivity and specificity of the CAMCOG were alsocalculated. Examination of the distribution of scoresshowedthe optimal cut-off to be 79/80. This yields92¾sensitivity and 96¾specificity. Only one organically

TABLE IIITotal scores for the Cambridge Cognitive Examination(CAMCOG) and the Mini-Mental State Examination

(MMSE) in the major diagnostic groups

Mean and range Mean and rangeof CAMCOG of MMSE

scores scores(maximum = 106) (maximum =30)

TABLE IIInter-rater reliability of sections of CAMDEX

mixed by the observer, and one of the three cases diagnosedas mixed was classed as SDAT by the observer.

Agreement on subsections of the scales

The 4'coefficientwascalculatedfor each itemin SectionsA, B, C and H of the CAMDEX. Table II presents themedian and range of these values.

It will be seen that all the median coefficients for sectionsare high. The lowest value obtained was derived from therecord of observed behaviour (Section C) independently setdown by the two psychiatrists, but at 0.83 this section maybe judged satisfactory and to show an acceptable degreeof inter-observer agreement.

Some idea of the reliability of the items can be obtainedfrom the range of 4' coefficients estimated for the differentitems in each section. The item with the lowest reliability inSection A was the judgement by the psychiatrists as to whetherphysical disability accounted for the patients' inability todeal with household tasks (4' 0.28). The item with lowestreliability in the cognitive examination (Section B) concernedthe naming of as many different animals as possible in aminute (4' 0.30). This wide disagreement was traced to thefact that one of the raters had excluded fish or birds. Thepoorest item in the observation section (Section C) was“¿�Speechvery slow. Pauses between the words―(4' 0.33).In such cases, scoringinstructions have been made moreexplicit to increase reliability in the revised version.

The answers recorded from relations or carers (SectionH) showedverygood agreementbetweenraters. The itemwith the lowest 4, coefficient was “¿�Doeshe/she havedifficulty in knowing where he/she is or in recognizingyou?― (4,0.53). This is probably too terse and ambiguousfor lay persons and has been made more specific in revision.

However, the proportion of items with low 4' coefficientsprovedrelativelysmall.Thegreatmajorityof itemsreachedan acceptably high inter-rater reliability.

Correlations between the total scores obtained by the twopsychiatrists for each section are also shown in Table II. Thecorrelations are all high and very significant statistically.

Cognitive performance

The results presented here were for the whole sample of92 patients. The diagnoses in the total group were 17

704 ROTH ET AL

impaired patient was misclassified by this instrumentcompared with four who were misclassified by the MMSE.

Several patients obtained maximum or near maximumscores on the MMSE. Sixteen patients scored 27+,including five depressed and one clouded patient. Fivepatients scored 29+ (three normals, two depressed), thehighest score (30) being obtained by a depressed patient.In contrast, only two patients, both normals obtained aCAMCOG score of 100+ while an additional two (onenormal, one depressed) scored within 10 points of themaximum, and a further five (two normal, three depressed)scored within 20 points of the maximum. These findingsdemonstrate that CAMCOG can discriminate betweenindividuals even at the high end of the ability range.

Severity of dementia and cognitive function

The relationshipbetween cognitiveperformance andseverity of dementia was examined by correlating both the

dementia score (Blessed et al, 1968) and the clinical ratingof severity of dementia with scores on the cognitive tests.

For the group as a whole, all correlations were highlysignificant (P<0.000). The dementia score correlated—¿�0.70with the CAMCOG and —¿�0.66with the MMSE.The clinical rating of severity of dementia correlated —¿�0.78with the CAMCOG and —¿�0.76with the MMSE. There wasa correlationof 0.94betweenthetwo cognitivetestsand0.68 between the dementia score and the clinical rating ofseverity.

The dementia score correlated significantly with each ofthe eight subscales of the Cambridge Cognitive Examination(orientation, language, memory, praxis, attention, abstractthinking, perception and calculation). The clinical ratingof severity of dementia also correlated highly with thecognitive subscales (P<0.000 for all comparisons).

Within the demented group as a whole (n = 49) there wasvery good agreement between cognitive performance andthe clinician's estimate of severity of dementia. Thecorrelation was —¿�0.83 for the total score on the CAMCOGand —¿�0.69for the score on the MMSE. The correlationwas highly significant for each of the eight cognitivesubscales, the highest correlation being obtained forlanguage (—0.77) and the lowest for attention (—0.40,P= 0.004).

Subjective assessment of cognitive function

Cognitive function was reported subjectively by the patientin Section A of the CAMDEX and reported by theinformant in Section H. We examined the relationshipbetween this type of information and objective measuresof cognitive performance. Three questions in Section A wereconcerned with the patient's self-assessment of memory;a general question about memory difficulty, a questionabout misplacing objects and a question about losing one'sway in familiar surroundings. None of these correlatedsignificantly for the group as a whole, with performanceon the memory items or any other measures of cognitiveperformance. Questions about difficulty with concentration, slowing of speech or slowing of thoughtsalso failed to correlate significantly with cognitiveperformance. On the other hand, the responses of

informants to five questions about memory, concentrationand muddled thinking, all correlated highly (P<0.00l) withtotal score on the CAMCOG and (P<0.0l) with seven ofthe eight cognitive subscales (orientation, language,memory, praxis, attention, abstract thinking, perception)while allfailedto correlatewith the calculationsubscale

and a measure of reading ability.A question about word-finding difficulty was also asked

of both the patient and the informant. Patient's self reportdid not correlate significantly with objective measures ofnaming or verbal fluency although it correlated significantlywith measures of verbal memory (P<0.0l). Theinformant's evaluation of the patient's word-findingdifficulty correlated significantly (P<0.0l) with bothnaming and fluency,and witheachof themain cognitivesubscales except memory.

In general it may be concluded that the patient's selfreport of cognitive function bears no relation to cognitiveperformance whereas the informant's judgment providesa reliable guide. Consistent with this is the absence of anysignificant correlations between patients' and informants'reports of the patient's of cognitive function.

Depressed mood and cognitive function

In addition to making a clinical diagnosis of depression andrating its severity,CAMDEXpermits depressedmood tobe assessed in all patients. This is done by; (a) self reporton 20 items from Section A relating to the signs andsymptoms of depression which were added together toprovide a depression severity scale, and (b) the informant'sresponse to the question, “¿�Doyou think he/she isdepressed?―. We examined the relationship between thesemeasures and cognitive performance.

For the group as a whole, scores on the depressionseverity scale are significantly related to orientation andmemory performance (P<0.01) but not to any othermeasure of cognitive performance. The informant's assessment of depressed mood correlated significantly (r= 0.30,P<0.0l) with scores on the depression severity scale butnot with any measure of cognitive function.

Responses to a key item in the depression severity scale(“Doyou feel sad, depressed or miserable?―) were foundnot to be related to cognitive performance, but correlated0.64 (P<0.00l) with informant's assessment of depression.These findings indicate that the presence of the signs andsymptoms of depression is related to impaired memoryfunctioning but complaints about depressed mood are not.

Development of the clinical diagnostic scales

The number of patients in the SDAT, MID and depressedgroups was sufficiently large to consider the developmentof a diagnostic scales from items in the CAMDEX. Thefirst stage was to select items considered, on clinicalgrounds, to be of possible use in making differentialdiagnoses. The frequency distribution of these items wasdrawn up for all diagnostic groups recorded on theCAMDEX and those items which proved to differ infrequency between diagnostic groups were selected for thedevelopment of three diagnostic scales. The first intended

ORGANICITY SCALE Eli

DIAGNOSIS OF MENTAL DISORDER BY CAMDEX

SCALE SCORES ADJUSTED FOR SCALE MEAN (SCORE/MEAN a 100)

FIG. 1. Mean scores on diagnostic scales for four diagnostic groups. (Scores adjusted for scale score mean.)

705

zMID SCALE

DEPRESSION SCALE

(ADJUS1

SDAT MID DEPRESSIONNORMAL

as a scale for SDAT consistedof 18items and proved tobe a scaleof organicityin general. The secondwas a scalefor MID which consisted of 12 items, and the third fordepression consisting of 14 items. The scores on thesesubscales plotted by the diagnosis made on the basis ofoperational diagnostic criteria is illustrated in Fig. 1.

The cumulativefrequencycurvesof the scores in eachscalewereplotted for SDAT, MID, depressedand normalgroups, (Figs2,3,4). Thesegraphswereusedto determineoptimal cut-off points for diagnosis. The proportion ofcorrectly classified patients using these optimal cut-offpoints is shown in Table IV.

DISTRIBUTION OF ORGANICITY SCORES - 4 DIAGNOSTIC GROUPS

7-,,+â€o@,

I,

@@,9―

44/

// @+

/, ,,e

NORMAL,# ,-_

—¿�4 -

MID

SDAT

.100

CUMULATIVEPERCENTAGE

OF 5CDIAGNOSTIC

GROUPDEPRESSION .—•

0 10 20

ORGANICITY SCORE (RAW)

FIG. 2. Distribution of scores on organicity diagnostic scale for normal, depressed, SDAT and MID groups.

NORMAL

706 ROTH ET AL

DISTRIBUTION OF MID SCORES - 4 DIAGNOSTIC GROUPS

-.4

+

NORMAL

DEPRESSION —¿�i

+- -. -4

CULMULATIVEPERCENTAGE

OFDIAGNOSTIC

GROUPA

MID

SDAT

1@

MID SCORE (RAW)

4

Fic. 3. Distribution of scores on MID diagnostic scale for normal, depressed, SDAT and MID groups.

The statistical significance of the diagnostic differentiation between the groups at these cut-off points wastested, using x2 tests and Fisher's exact test. Using acut-off point of 4, the organicity scale differentiatedbetween SDAT patients and normals (P<0.000l) anddepressed patients (P<0.0005) but did not differentiate

between SDAT and MID. A cut-off point of 2 on the MIDscaleproducedsignificantdifferencesbetweenMID casesand normals (P<0.0l), SDAT (P<0.000l) and depression(P<0.001). A cut-off point of 10 on the depressiondiagnostic scales produced significant differences betweendepressed patients and normals (P<0.0001), SDAT

DISTRIBUTION OF DEPRESSION SCORES - 4 DIAGNOSTIC GROUPS

CUMULATIVEPERCENTAGE

OFDIAGNOSTIC

GROUP

__0@

‘¿�V --- +

,‘ ,__4_

DEPRESSION •¿�—•

MID +- ---4

SDAT

DEPRESSION SCORE (RAW)

Fic. 4. Distribution of scores on depression diagnostic scale for normal, depressed, SDAT and MID groups.

Organicity scaleMID scaleDepression scaleCut-off

score%Correctly

classifiedNormalSDA

T MIDDepression4

210100

9510085

85 9285 85 83

100 85 75

ClinicalscaleDementiaDepressionOrganicity0.73―—0.11MID0.28―0.15Depression—0.250.74―

Organicity—0.61―0.190.13—0.63―MID—0.27―—0.10—0.01—0.25'Depression0.21'—0.120.020.22'

707DIAGNOSISOF MENTAL DISORDERBY CAMDEX

the scalewas a rational measure. It is, of course, to be notedthat the absence of a correlation simply would leave thevalidity question open since the test does not propose arelationship of any hypothetical kind.

Items from the cognitive section were subjected to aprincipal component analysis and the resulting factor scoresof the first three factorswerealsocorrelatedwith the threescale scores. The pattern of results for Factor 1, a generalfactor, was strikingly similar to that obtained for the totalscore on CAMCOG as a whole (Table V). Both correlatedhighly with the organicity scale giving substantial supportfor its validity. There is also a smaller but statisticallysignificant correlation with the MID and depressiondiagnostic scales.

The organicity and MID scales also correlated significantlywiththe psychiatricglobalratingof dementiathoughnot withglobalratingsof depression.The reversewastrueof the depressiondiagnosticscalewhichcorrelated highlywith the clinical global rating of depression (Table VI).

TABLE VICorrelation coefficients between clinical diagnostic scales

and global ratings of severity

TABLE IVClassjfication of diagnoses by clinicaldiagnostic scalesusing

approximate cut-off points

(P<0.0001) and MID (P<0.0l). It has to be borne in mindof course that there can be no complete differentiation sincethe conditions are not mutually exclusive in reality as isprobably reflected in cases of depression and MID.

The independence of the three scales was tested bycalculating their inter-correlations. These showed that therewas a high degree of independence between the depressionscale and the other two scales (r = —¿�0.15 and 0.18 fororganicity and MID scales respectively) although asignificant relationship between the organicity and MIDscales was found.

A test of reliability of the scales was made by an oddeven-split-half method. The reliability coefficients werecorrectedto fulllengthand are shownbelow.A particularlyhigh level of reliability is shown for the organicity scale(0.95). The other two scales for depression (0.90) and MID(0.77) seem quite acceptably reliable.

The problem of validity is difficult. A clinical diagnosismade under these circumstances cannot be fully independentof responses to items in the scale since the items are basedon similar considerations to those on which clinicaljudgement is based. This is, of course, substantially whythe items are included in the scale at the outset. Equallythe expectations resulting from a clinical diagnosis probablycreate somebias in the evaluationof responsesto the scaleitems, where the scale is administered by the diagnostician.Difficulties of this kind are incapable of complete resolutionand validation becomes a progressive process of iterations,in which many varied sources of information must be used.In the present research the scales described are derived onlyfrom clinical data and, therefore, it is possible to turn tothe cognitive section to look for validation. A positivecorrelation would show a relationship between a scale andsome aspect of cognitive performance such as to indicate

TABLE VCorrelations between clinical diagnostic scales andfactors

derived from cognitive items

Factor 1 Factor 2 Factor 3 Total score(66.5%) (9.5%) (6.7%) on CAMCOG

“¿�P<O.Ols'*P<o.oooI

Eight of the 18 items in the organicity diagnostic scaleare itemswhichalsoappearin the NewcastleDementiaScalefor severity of dementia (Blessed et a!, 1968) and there istherefore a high correlation between the two scales (0.95)although the Blessedscale did not differentiate satisfactorilybetweendiagnostic groups.

Discussion

In this paper we have described a diagnostic andassessment schedule that seeks to evaluate allparameters of present state, history, observation andmeasurement that may be relevant for the purposeof diagnosis and quantitative gradation of dementia.

Each section of the CAMDEX has been found tohave an acceptably high measure of inter-observerreliability and this holds also for the great majorityof individual items. The measure of agreementbetween different psychiatrists in respect of broadcategories of diagnosis has also proved satisfactoryand compares favourably with figures for interobserver agreement in published schedules directedat the problem of diagnosis alone (Henderson et a!,1983). Data relating to test and re-test reliability arefor the present limited; there are special problemsattaching to the administration within a short period

(Figures in brackets are variance explained by each factor)‘¿�P<O.05

“¿�P<O.Ol“¿�P<OOOl

708 ROTH ET AL

of a long assessment schedule to elderly individuals.However, agreement between test and re-test within3 weeks in a small number of cases is good.

The CAMCOG score in the cognitive sectionproved to have a high sensitivity and specificity indifferentiation between organic and non-organiccases and was highly correlated with the BlessedDementia Scale and the psychiatrist's clinical ratingof severity.

Two principal advantages which the CAMCOGhas over the widely used Mini Mental StateExamination (Folstein et a!, 1975) are (i) it coversa broader range of cognitive functions (ii) it detectsmild degrees of cognitive impairment and (iii) itavoids ceiling effects.

Comparisons between information obtained frompatients and their relatives indicates that relativesmay be unaware of depressed mood but are far betterat assessing cognitive impairment than are patientsthemselves.

The diagnostic scales derived from the sampleshow a relatively good classification rate; are reliableas shown by the split half reliability and have someevidence of validity, inferred from their correlationswith global clinical ratings and with cognitiveperformance. These scales must now be tested on anew population so that their utility can be assessed.In the longer term it is planned to use these as thebasis for computerised diagnosis, along the lines ofthe CATEGO classification (Wing et a!, 1974) andthe AGECAT classification newly developed byCopeland and his colleagues for the GMS, in whichorganic psychosis is treated as a single category.

It is intended to investigate the validity of theCAMDEX schedule in a number of different ways,including long-term follow-up studies and correlationwith pathological and biochemical measures. Examination of cognitive change in the follow-up studieswill be of particular importance for the derivationof valid criteria in the diagnosis of early and milddementia and depressive pseudo-dementia. Postmortem studies of the brain should also provevaluable to this end in addition to shedding light onthe structural and neurochemical changes associatedwith the early stages in the development of dementiawhich are for the present largely unknown.

For the present the CAMDEX has proved itselfof value as an instrumental aid in clinical diagnosis.When determined with the aid of CAMDEX,diagnoses have shown an acceptably high measureof inter-observer correlation. To develop theCAMDEX to the next stage will require additionaldata derived from the independent methods ofvalidation which have been suggested in this sectionof the paper.

Acknowledgements

This research was supported by Project Grants from the MedicalResearch Council.

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*Sir Martin Roth, MA, MDCantab, Sc.D.Hon., FRCP, FRCPsych,Professor Emeritus of Psychiatry, Universityof Cambridge; E. Tym, MB, Ch.B., MRCPysch,DPM, Consu!lant Psychogeriatrician, HinchingbrookeHospita!; C. Q. Mountjoy, MB, FRCPscyh,DPMConsultant Psychiatrist, St Andrew's Hospita!, Northampton;F. A. Huppert, PhD, University Lecturer, Department of Psychiatry, University of Cambridge MedicalSchoo!; H. Hendrie, MB, Ch.B, The Institute of Psychiatric Research, Indiana University; S. Verma, MD,Associate Professor of Psychiatry, Michigan State University; R. Goddard, MB, MRCPsych,Senior Registrar,West Suffo!k Hospita!.

*Correspondence: LevelS, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, UK

(Accepted 9 January 1986.)

The CAMDEX is available to interested investigators at a small fee to cover reproduction costs. Enquiries should be addressed to:Dr Felicia A. Huppert, Department of Psychiatry, Level 4, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, UKSirMartin Roth,LevelS,Addenbrooke'sHospital,HillsRoad, Cambridge CB2 2QQ, UK