BRIEF COMMUNICATION

Retrospective data for diabetic foot complications: only thetip of the iceberg?P. R. Wraight,1 S. M. Lawrence,1,2 D. A. Campbell2 and P. G. Colman1

1Department of Diabetes and Endocrinology and 2The Clinical Epidemiology and Health Services Evaluation Unit, The Royal Melbourne Hospital,

Melbourne, Victoria, Australia.

Key words

diabetes, diabetic foot, retrospective review.

Correspondence

Dr Paul Wraight, Department of Diabetes and

Endocrinology, The Royal Melbourne Hospital,

Grattan Street, Parkville, Vic. 3050, Australia.

Email: paul.wraight@mh.org.au

Received 6 May 2005; accepted

10 November 2005.

doi:10.1111/j.1445-5994.2006.01039.x

Abstract

Admission rates for diabetes-related foot complications to anAustralian hospital

were assessed by comparing the frequently used method of retrospectively

identifying patients according to International Classification of Diseases (ICD)

codeswith that of prospectively identifyingpatients at the timeof admission. The

aim was to determine the true admission rate of diabetes-related foot compli-

cations and to assess the ability of ICDdischarge codes to accurately represent the

clinical severity of each identified admission. The retrospective study of ICD

codes identified approximately one-third of the patients admitted during the

prospective studies. Furthermore, ICD codes allocated in the prospective studies

failed to accurately represent the clinical condition in 61% of cases and the

corresponding Weighted Inlier Equivalent Separations weighting resulted in

a $215 000/year deficit for admissions to a single hospital.

In many countries, including Australia, diabetes has been

identified as anational healthpriority. This actionhas been

undertaken because of epidemiological data that show the

continuing rise in the incidence of diabetes and its related

complications.One such complication, that has beenunder-

valued as a source of major morbidity and mortality

for patients with diabetes, is that of diabetes-related

foot complications. This complication includes a diverse

group of clinical conditions, such as ulceration, cellulitis,

wound infection, osteomyelitis, gangrene and Charcot

joint, which have collectively been shown to not only

be the leading cause of nontraumatic lower limb ampu-

tations, but to also use more days of hospitalization than

any other diabetes-related complication.1,2

Over the last decade extensive research relating to the

prevalence, investigation and management of these com-

plications has been published, but much of this data have

been based on retrospective studies, in which cases have

been identified by International Classification of Diseases

(ICD) codes. With concerns about the accuracy of these

data, we have undertaken both a retrospective and two

prospective studies to identify the ‘true’ admission fre-

quencyof diabetes-related foot complications and to deter-

mine the accuracy of retrospective studies to collect such

epidemiological data.3 The study design has also allowed

us to review the accuracy of the codes allocated to patients

on discharge, within the prospective studies. This coding

information is important in defining the complexity of the

individual cases and, at least inVictoria, in determining the

payment to the hospital for the admission episode.

A retrospective electronic search of ICD codes for dia-

betesmellituswasundertaken for a12-monthperiod, from

1 July 1999 to 30 June 2000, with the hope of identifying

all individuals admitted with diabetes-related foot com-

plications to The Royal Melbourne Hospital (RMH). Both

diabetes with foot-specific codes (e.g. diabetes mellitus

with ulceration) and diabetes with non-specific complica-

tionswere included in the search. This resulted in a total of

53 ICD codes being used with 733 admissions being iden-

tified. Each admission was reviewed within the electronic

database for patient admission details and the histories of

those identified to have or potentially be at risk of having

diabetes and/or a diabetes-related foot complication were

manually reviewed.3Funding: None

Potential conflicts of interest: None

Internal Medicine Journal 36 (2006) 197–199

ª 2006 Royal Australasian College of Physicians 197

Subsequently, two prospective studies each of 2months

duration, from 2 April 2002 to 31 May 2002 and from 13

November 2002 to 11 January 2003, were undertaken to

identify all admissions to RMH with diabetes-related foot

complications. A computer print out of all new admissions

to the hospital was obtained daily and the hospital inpa-

tient notes of all newly admitted patientswere reviewed to

identify those with a diabetes-related foot complication. If

doubt remained from the documentation in the medical

history, one of the investigators visited the patient and

examined their feet. Information on individual patient

assessment, investigations, management and clinical out-

comes was collected continuously for the whole duration

of the patient’s admission.

After completion of the prospective studies, the data

collected on each patient admission were processed by the

medical coders, to create ICD codes and Weighted Inlier

Equivalent Separations (WIES). The calculation of WIES

weightings is an essential component indetermining fund-

ing of acute admissions to Victorian hospitals. It is believed

that the study ICD codes and WIES weightings more

accurately represent the clinical situation of each admis-

sion, and so were used as the reference standard to which

codes, allocated by medical coders by the standard process

of reviewing inpatient notes/discharge summaries, could

be compared.

The retrospective study identified 69 admissions for

50 individuals over a 12-month period.3 The first of the

2-month prospective studies identified 34 admissions for

32 patients and the second 30 admissions for 28 patients.

Assuming a constant flowof patients at this rate,wewould

expect between 180 and 204 admissions over 12 months,

or a mean of 192 patients per year admitted with foot

complications. These figures represent a nearly threefold

increase in thenumbers identified prospectively compared

with those identified in the retrospective study. Therefore,

previous studies that have reported epidemiological data,

obtained by retrospectively identifying patients by ICD

codes, are likely to have grossly underestimated the true

effect that diabetes-related foot complications are having

on the health system.

Even though a period of 22 months exists between the

retrospective and first prospective study, there was no

significant change in referral base, overall hospital admis-

sion rate or in hospital policy with regard to admission and

management that would explain the difference in admis-

sion rates. A change that did occur between the retrospect-

ive and prospective studies, and may have altered the

admission rates, was that there was an increase in referrals

from the Emergency Department to the Hospital in the

Home and Royal District Nursing Services. With more

patients being managed at home during the prospective

study, we would expect a reduction in the admission rate

during this time rather than the observed increase. A

second change that occurred during the study period

was an upgrade in the edition of the ICD code manual.

Even though a specific diabetic foot code was introduced

between the retrospective and prospective studies, this

would not influence our results.

Several factors were identified that may explain the

large discrepancy in identification rates between the retro-

spective and prospective studies. The most significant

causative factor identifiedwas the lack of clear and concise

medical notes in the patient record; these notes have the

most weight in assisting coders to assign appropriate ICD

codes. Second, although inherent coding anomalies exist,

they contributed to only approximately 10% of the over-

all problem. A third contributing factor was the failure of

clinical assessments to identify coexisting conditions at

the time of presentation. For example, a patient present-

ing with cardiac failure, but also having a diabetes-related

foot ulcer, may receive appropriate wound care by nurs-

ing and allied medical staff, but because the medical team

are either not aware of its presence or are not directly

managing this condition it is unlikely that it will be listed

on the discharge summary. Finally, the design of the

prospective studies, in which patients were identified by

study investigators to have a diabetes-related foot com-

plication even though the treating teammay not be aware

of the fact, may have led to an increase in identified cases.

However, this would only account for approximately 18%

(36 of the projected 192 admissions per year) of all

patients admitted to each of the prospective studies. Fur-

thermore, failure to recognize and document their pres-

ence would have a negative effect on retrospectively

identified incidence data, underestimating the patient’s

clinical problems and reducing the financial return for

the hospital.

Within the prospective studies, comparison of diagnoses

(principal, additional diagnoses) allocated by medical

coders after review of the patient history and discharge

summaries at discharge with those diagnoses allocated

after review of the study data showed important differ-

ences. Of the 30 and 34 admissions identified in the two

prospective studies, 17 (56.7%) and 21 (64.7%) had ICD

codes allocated at routine discharge coding that were

inaccurate or underestimated the clinical complexity com-

pared with those allocated after prospective review of the

study data (Table 1). Ifwewere to only include admissions

where the primary reason for admission was for diabetes-

related foot complication, 43% of individuals in both

prospective groups still had an inaccurate ICD code. Fur-

thermore, approximately one-third of patients in both

prospective groups would not be identified in a retrospect-

ive review because of failure to list diabetes or diabetes-

related foot pathologies in the diagnosis lists.

Wraight et al.

198 ª 2006 Royal Australasian College of Physicians

The reported diagnoses, achieved through reviewing

patient histories in the standard fashion at discharge com-

pared with those achieved by using the prospective study

data, resulted in considerable differences in the finalWIES

weightings calculated for each admission. Within the two

prospective studies, 13/30 (43%) and 13/34 (38%) of

admissions had a change to their diagnosis list that resulted

in an increase in theWIES weighting. TheWIES weighted

correction resulted in an increase in WIES costing of

approximately $36 600 for 2 months in the first prospect-

ive study and $35 200 for the second 2-month study. This

corresponds to an annual costing deficit, for a single ter-

tiary hospital, of more than $215 000 for admissions

related specifically to diabetes-related foot complications.

Approximately 30% of the WIES weighted correction for

each study group occurs as a result of admissions where

a diabetic foot complication is not the presenting com-

plaint.No reduction inWIESweightingoccurred as a result

of changes to diagnoses lists.

Although the study we undertook was specific to

diabetes-related foot complications, the findings are not.

Research by Griffiths and Hindle showed that of 386

randomly selected histories, identified by the fact that they

contained at least one diabetes diagnosis in the discharge

summary, 33% were deemed inaccurate and required a

change in their coding.4 They reported that the type of

diabetes was rarely reported and 40% of records failed to

code treatments for diabetes-related conditions. Similarly,

in a prospective study undertaken by Leslie et al., 61% of

individuals admitted with diabetes were not allocated a

code to identify this diagnosis.5 These errors support our

contention that coding datawould be an inaccuratemeans

to collect reliable epidemiological data.

In conclusion, clinical decisions and health policy must

be based on evidence derived from well-executed and

methodologically strong studies. Our study clearly shows

several shortcomings that exist if results of retrospective

studies of reported ICD codes are accepted without ques-

tion as the basis for health services funding and resource

allocation.

References

1 Pliskin M, Todd W, Edelson G. Presentations of diabetic feet.

Arch Fam Med 1994; 3: 273–9.

2 Gibbons G, Eliopoulos G. Infection of the diabetic foot. In:

KozakG,Hoar C Jr, Rowbotham J,Wheelock F Jr, Gibbons G,

Campbell D, eds. Management of Diabetic Foot Problems:

Joslin Clinic and New England Deaconess Hospital.

Philadelphia: W.B. Saunders; 1984; 97–102.

3 Lawrence S, Wraight P, Campbell D, Colman P. Assessment

and management of inpatients with acute diabetes-related

foot complications: room for improvement. InternMed J 2004;

34: 229–33.

4 Griffiths R, Hindle D. The effectiveness of AN-DRGs in

classification of acute admitted patients with diabetes.

Health Inf Manag 1999; 29: 77–83.

5 Leslie P, Patrick AW, Hepburn DA, Scoogal IJ, Frier BM.

Hospital in-patient statistics underestimate the morbidity

associated with diabetes mellitus. Diabet Med 1992; 9:

379–85.

Table 1 Factors preventing the more appropriate allocation of ICD codes

in the prospective study groups

Factor % of total group

with inaccurate

ICD allocation

Failure to identify/document a foot complication

to be related to the individuals’ diabetes. If the

condition is not described in the context

of a ‘diabetic foot’-related problem, then a

lesser code relating to a nondiabetic foot

complication will be allocated.

34

Failure to document the presence of osteomyelitis

once the diagnosis has been confirmed.

Osteomyelitis is often queried as a complicating

condition of a foot ulcer, but without clear

documentation that the diagnosis has been

confirmed with appropriate investigations,

appropriate codes cannot be allocated.

21

Failure of admitting units to identify and

document the coexistence of a ‘diabetic

foot’ complication during an admission for

a separate primary medical condition.

18

Failure to document the occurrence of

debridement.

11

Coding anomalies (e.g. ordering of diagnoses,

coding for Charcot joint).

11

Failure to document the presence of a

specific condition (e.g. gangrene).

5

ICD, International Classification of Diseases.

Retrospective data for diabetic foot complications

ª 2006 Royal Australasian College of Physicians 199