The Fibromyalgia Impact Questionnaire: AUseful Tool in Evaluating Patients withPost–Lyme Disease Syndrome

John Fallon, Danuta I. Bujak, Sara Guardino, and Arthur Weinstein

Objective. To determine the reliability and valid-ity of a modified version of the Fibromyalgia ImpactQuestionnaire (FIQ) in evaluating patients with post-Lyme disease syndrome (PLDS).

Methods. In this cross-sectional analysis 13 PLDS,18 fibromyalgia (FM), and 16 healthy controls (n 5 47)completed a modified FIQ containing items to evaluatephysical impairment, symptom severity, and globalwell-being. Comparisons between groups were doneusing analysis of variance with a significance level setat 0.05.

Results. PLDS patients demonstrated statisticallysignificantly greater levels of impairment than con-trols in physical functioning, FIQ total score, globalwell-being, joint pain, fatigue, depression, ability toperform activities of daily living, and memory/con-centration. FM patients demonstrated a statisticallysignificantly greater level of impairment than the

control group in all categories, and the scores weresignificantly higher than the PLDS group in the mea-surement of physical impairment, FIQ total score,muscle pain, and joint pain. Overall, the instrumentpossesses good reliability and validity, although ad-equacy of this instrument to measure impairment inthe male PLDS population needs further elucidation.

Conclusion. The results of this study suggest thatthe modified FIQ may be a useful tool in evaluatingPLDS patients. The findings suggest that there maybe some differences in the etiopathology of the symp-toms experienced by PLDS and FM patients.

Key words. Post–Lyme disease syndrome; Fibro-myalgia; Fibromyalgia Impact Questionnaire; Lymedisease.

INTRODUCTION

The persistence of arthralgia, myalgia, chronic fa-tigue, depression, and neurocognitive symptoms in asubset of Lyme disease patients, despite even re-peated or prolonged antibiotic treatment, has beenwell documented (1–8).

Several investigators have noted the similarity be-tween these chronically symptomatic patients withpost–Lyme disease syndrome (PLDS) and patientsdiagnosed with fibromyalgia (FM) (2,3). As part of alarger study investigating the pathogenesis of PLDS,we examined the validity and reliability of a modi-fied version of the Fibromyalgia Impact Question-naire (FIQ; 9) as a tool for the clinical evaluation ofpatients with PLDS. In particular, we were interestedin whether this form of the FIQ could be used toevaluate physical impairment, symptom severity,

Supported by grants from NIAMS (1RO1AR-4313) and NIAID(NO1-AI-65308).

John Fallon, MS, FNP, The Leinhard School of Nursing, PaceUniversity, Pleasantville, New York; and Danuta I. Bujak, PhD,FNP (current address: University of Maryland, School of Nursingand School of Medicine, Baltimore), Instructor in Medicine, SaraGuardino, BA, Research Assistant, and Arthur Weinstein, MD(current address: The George Washington University MedicalCenter, Washington, DC), Professor of Medicine and DivisionChief, Division of Rheumatic Diseases and Immunology, NewYork Medical College, Valhalla, New York.

Address correspondence to Arthur Weinstein, MD, Division ofRheumatology, The George Washington University Medical Cen-ter, 2150 Pennsylvania Avenue, NW, Washington DC 20037.

Submitted for publication December 18, 1997; accepted in re-vised form June 15, 1998.

© 1999 by the American College of Rheumatology.

42 0893-7524/99/$5.00

and global well-being in these patients and in deter-mining the differences that might be demonstratedbetween PLDS and FM patients.

PATIENTS AND METHODS

Patients. Patient selection was determined by thestandards used for the larger ongoing study of PLDSpathogenesis (10).

The enrollment criteria for PLDS patients were:1) meeting the established 1990 Centers for Dis-ease Control criteria for Lyme disease at time oforiginal illness; 2) having received at least onecourse of recommended oral or parenteral antibi-otics for at least 2–3 weeks at recommended doses;3) prior or current positivity to anti-Borrelial anti-bodies by Western blot; 4) 6-month or longer his-tory of widespread musculoskeletal pain and fa-tigue that began simultaneously with or after thediagnosis of Lyme disease, without significantprior history; 5) no evidence of severe clinicaldepression; and 6) no evidence of active Borrelialinfection at evaluation and no other medical con-dition to account for the symptoms.

For FM patients enrollment criteria were: 1) meet-ing the American College of Rheumatology criteriafor fibromyalgia (11); 2) no evidence of clinical de-pression or other systemic illness to account forsymptoms; and 3) negative Lyme serology.

For healthy controls, the following criteria wereused: 1) age- (6 2 years), gender-, and race-matched to the PLDS group; 2) in general, goodhealth with no history of Lyme disease or FM; and3) no symptoms that might indicate the presenceof Lyme disease or FM.

Instrument selection. The patients completed amodified version of the FIQ (9). The original FIQconsists of 19 items, the first 10 of which are evalu-ated collectively to provide a single score of physicalimpairment. This physical impairment measure-ment focuses on the ability of patients to performlarge muscle tasks during the previous week, witheach item being rated on a 0–3 Likert-style scaleranging from always being able to perform a task 5 0,to never being able to perform a task 5 3. Item 11 hassubjects identify the number of days in the past weekthat they felt good. Item 12 measures the number ofdays in the last week that subjects were forced tomiss work because of their illness. The remaining 7items on the original instrument consist of 10-cm long horizontal anchored visual analog scales(VAS) on which the subjects rated the impact of

illness during the previous week on their ability towork, the severity of pain, fatigue, how rested theyfelt after sleeping, stiffness, anxiety, and depression.Subjects were instructed to skip items 12 and 13(impact of illness on ability to do job) if they did notwork outside the home.

The principal modifications to the FIQ used in thisstudy consisted of the addition of two new visualanalog scales—one evaluating memory/concentra-tion problems (item 22) and the other the ability toperform essential self-care activities of daily living(ADL) (item 21)—and the division of the single scaleevaluating pain into two distinct scales, one for mus-cle pain (item 14) and one for joint pain (item 15).The addition of the memory/concentration questionwas intended to assess the subjective intensity of theneurocognitive symptoms reported by many Lymedisease and PLDS patients, and to see how the re-ported level of impairment among PLDS subjectscompared with that of FM patients. The two itemsassessing muscle and joint pain were designed notonly to look for differences between PLDS and FMpatients, but also to see to what degree patientscould distinguish the nature of the pain they wereexperiencing. The only other structural change madefor this study was to place each of the VAS questionson a different page of paper to guard against theanswer for one question directly influencing the an-swer for another due to direct comparison.

The administration and scoring of the FIQ wasperformed according to the manner prescribed byBurckhardt et al (9). Instructions for completing theFIQ were explained to the subjects by one of theinvestigators, and the instrument was then self-administered with an investigator available to helpthe subject with any questions.

The PLDS and FM patients were seen at New YorkMedical College in 1995; the healthy controls wererecruited by the researchers at various sites and werenot evaluated at New York Medical College. Thisstudy was approved by the Institutional ReviewBoard of New York Medical College as part of thelarger study on the pathogenesis of PLDS.

Data analysis. All data were coded and enteredinto a computer database. The data were analyzedusing SPSS/PC-V6.0 software (12). Comparisons be-tween patient groups were performed using analysisof variance with a significance level set at P # 0.05,with assessment of differences between individualitems, physical impairment score, and FIQ totalscore (the sum of all items excluding 12 and 13)using the Scheffe post hoc test.

Four distinct issues were considered in the ana-

Arthritis Care and Research The FIQ in Post–Lyme Disease Syndrome 43

lysis and interpretation of the results: 1) the degreeto which the FIQ possessed internal and externalreliability for this patient population, 2) the extent towhich the instrument possessed content and con-struct validity, and 3) the similarities and differencesseen between FM and PLDS patients with this in-strument.

Reliability. Internal consistency of the FIQ forthis cross-sectional study was assessed using Cron-bach’s alpha. In order to check for variance betweenitems on the FIQ, a standardized item alpha was alsogenerated as was an “alpha if item deleted” test. Thiswas done in order to examine the reliability of theFIQ when each of the items was removed from thescale (13).

Validity. In the original development and valida-tion of the FIQ, the percentage of missing data forindividual items on the instrument was used as thecriteria for evaluating content validity (9). In addi-tion to using the same criteria for our analysis, weassessed the degree of impairment reported by PLDSpatients as compared with that experienced by theFM patients and the healthy controls.

Construct validity of the FIQ for a FM populationwas determined to be satisfactory in the originalstudy through factor analysis and correlations be-tween items on the FIQ and items on the ArthritisImpact Measurement Scales instrument (9). Becauseof the similarities between the symptomatic mani-festations of FM and PLDS, we chose to evaluateconstruct validity by examining the working hypoth-esis that the PLDS patients would demonstrate astatistically significantly (P # 0.05) higher level of

impairment than the healthy controls in terms ofphysical impairment, global well-being, and FIQ to-tal scores. In addition, the use of the “alpha if itemdeleted” provided additional insight into whethercertain items on the FIQ might not have as muchcontent or construct validity as would be desired.

RESULTS

In this cross-sectional analysis, 13 PLDS, 18 FM,and 16 healthy controls (age-, gender-, and race-matched to the PLDS patients) (n 5 47) completed amodified version of the FIQ.

Patients and controls. The demographic charac-teristics of participants (n 5 47) are summarized inTable 1. There were no statistically significant dif-ferences among the 3 groups with regard to age, race,or education. As expected, the FM group differedfrom the other two groups in terms of gender, as allparticipants were women. In addition, the FM groupdiffered from the PLDS group on illness duration, asmean length of time since disease onset was 7.95versus 3.8 years for the latter.

Results of the FIQ testing are summarized in Ta-bles 2 and 3. PLDS patients demonstrated statisti-cally significantly higher scores (P # 0.05) than con-trols in physical functioning, FIQ total score, globalwell-being, and VAS measures of joint pain, fatigue,depression, ability to perform activities of daily liv-ing, and impairment of memory and concentration,suggesting greater impairment. Differences betweenthe two groups were also seen in severity of musclepain, feeling rested after sleeping, stiffness, and anx-iety, but these were not statistically significant. FMpatients demonstrated a statistically significantlygreater level of impairment than the control group inall categories, and the scores were significantlyhigher than the PLDS group (P # 0.05) in the mea-surement of physical impairment, FIQ total score,

Table 1. Demographic characteristics of participants(post-Lyme disease syndrome [PLDS], fibromyalgia [FM],and controls)

PLDS(n 5 13)

FM(n 5 18)

Controls(n 5 16)

Men/women 5/8 0/18 8/8Race

Caucasian 12 (92.3%) 17 (94.4%) 14 (87.5%)African American 1 (7.7%) 1 (5.6%) 2 (12.5%)

Age, mean (range) 43.1 (20–67) 46.6 (35–63) 45.3 (22–67)Education, years,

mean 15.8 15 16.2Symptoms duration,

years, mean(range) 3.8 (3–12.8)* 7.95 (1–30)* NA†

* t-test P , 0.01.† NA 5 not applicable.

Table 2. Fibromyalgia Impact Questionnaire(FIQ) scores*

FIQPLDS

(n 5 13)FM

(n 5 18)Controls(n 5 16)

FIQ total score 50.12† 98.03‡ 14.02Physical impairment (total) 2.23† 4.88‡ 0.07Global well-being 5.28† 7.23† 0.72

* Analysis of variance , 0.05. PLDS 5 post-Lyme disease syndrome; FM 5fibromyalgia.† Significantly different from controls.‡ Significantly different from PLDS and controls.

44 Fallon et al Vol. 12, No. 1, February 1999

muscle, and joint pain. The severity of symptomsdid not correlate with their duration (P . 0.05).

Reliability. The overall alpha coefficient with allitems included was 0.72 (n 5 35). Twelve caseswere dropped from analysis due to lack of data foritem 12 (subjects did not work outside home). Anadditional analysis showed that excluding item 12only raised the alpha to 0.74 when all 47 caseswere included, but excluding only item 13 (impactof illness on ability to do job) raised the alpha to0.93 (12 cases dropped). Excluding both items 12and 13 improved internal reliability by raising thealpha to 0.94 (all 47 cases analyzed). While anal-ysis of variance showed no statistically significantdifference between PLDS, FM, and healthy con-trols in regard to days of work missed (item 12),both the PLDS and FM groups demonstrated astatistically significantly higher level of impair-ment in their ability to do their jobs (item 13).

Content validity. Of the 10 items comprising thephysical impairment subscale (items 1–10), onlyitem 9, ability to do yardwork, and item 4, ability towash dishes, had more than 2 missing cases. A totalof 9 subjects (19.1%) did not do yard work, with 1PLDS subject, 5 FM subjects, and 3 controls leavingthis item blank. Four subjects, 3 FM and 1 control,did not wash dishes.

Construct validity. Construct validity of this mod-ified FIQ for the PLDS population was supported byconfirmation of our hypothesis that these patientswould demonstrate a statistically significantlygreater degree of impairment in physical function-

ing, global well-being, and symptom severity thanthe healthy controls.

DISCUSSION

This is the first study that has used the FIQ toevaluate patients with PLDS. The FIQ was selectedas a tool for this study for several reasons. First, theinstrument contains items to assess the broad rangeof symptomatic distress frequently seen in patientswith PLDS: physical impairment, diminished globalwell-being, arthralgia, myalgia, fatigue, difficultyperforming ADLs, stiffness, anxiety, depression, andmemory/concentration problems. Second, the FIQwas designed specifically for use in the clinical as-sessment of FM patients and has established test–retest reliability as well as content and constructvalidity for a specific patient population, and thuswould seem to be an ideal choice for an instrumentto examine the similarities and differences betweenspontaneous FM and the fibromyalgia-like symp-toms seen in PLDS patients. Third, it was attractiveas a concise tool that could be self-administered andcompleted by subjects within approximately 5 min-utes.

External reliability of the FIQ—stability of the in-strument determined through test–retest correla-tions—was established by Burckhardt et al in theiroriginal development and validation study on FMpatients (9). Initial studies have indicated that PLDSpatients tend to have chronic symptoms that persistover months and years similar to those observed inFM (1,3,10). Therefore, the test–retest reliability ofthe FIQ was deemed sufficiently well established tojustify extrapolation to the PLDS patient populationfor the purposes of this study.

The internal consistency of the instrument usingCronbach’s alpha indicated that items 12 and 13were not providing reliable information. In analyz-ing these findings we believe these items were prob-lematic for two reasons. The first had to do withinterpretation of the questions by subjects. Althoughsubjects were instructed not to respond to items 12or 13 if they did not work outside the home, some ofthose who did not work provided a number of daysmissed from work in the last week. The second prob-lem had to do with the time limitation of one week initem 12, as a number of patients commented thattheir illness had caused some change in their abilityto work but that this change was not necessarilyreflected in the number of days missed from work inthe past week. Burckhardt agrees that item 12 shouldbe deleted from the instrument because it seems to

Table 3. Fibromyalgia Impact Questionnaire visualanalog scale (VAS) scores by group*

VAS item no. (0–10 cm)PLDS

(n 5 13)FM

(n 5 18)Controls(n 5 16)

14. Muscle pain 3.33 6.62‡ 1.0315. Joint pain 4.15† 7.01‡ 0.8516. Fatigue 6.62† 7.74† 2.9817. Rest 5.34 7.52† 2.7618. Stiffness 4.58 6.70† 1.9119. Anxiety 3.42 4.99† 1.3120. Depression 4.92† 4.31† 0.9021. ADL impairment 4.62† 6.18† 0.7322. Memory/concentration

problem 5.62† 5.74† 0.76

* Analysis of variance P # 0.05. PLDS 5 post-Lyme disease syndrome;FM 5 fibromyalgia; ADL 5 activity of daily living.† Significantly different from controls.‡ Significantly different from PLDS and controls.

Arthritis Care and Research The FIQ in Post–Lyme Disease Syndrome 45

lack the accuracy and sensitivity to provide a goodcorrelation with symptom severity (Burckhardt CS:personal communication).

The internal consistency of the instrument alsoimproved significantly with the deletion of item 13.It is likely that the misinterpretation of items 12 and13 by some subjects contributed to this finding. Be-cause our study was initiated with items 12 and 13we did not change the method of administration asneither item is included in the final summation ofscores that produces a total FIQ score.

Overall, the FIQ demonstrated acceptable contentvalidity in this study. However, several male pa-tients commented that the tasks comprising thephysical functioning item were not truly representa-tive of the gross motor tasks that they consideredimportant in their daily or weekly routine. This wasimportant because of the gender differences in thepatient populations affected by FM and PLDS.Whereas more than 87% of FM patients tend to bewomen (12), and the development and validation ofthe FIQ was done with all-female samples (9), thePLDS population does not appear to have as pro-nounced a gender skew (1). In this study, while allthe FM patients were women, 5 of the 13 PLDSpatients (38.5%) were men.

Analysis of variance among all 3 groups on thephysical functioning item indicated that for severalof the tasks listed, the PLDS population experiencedrelatively little impairment. On item 2 (ability to dolaundry with a washer and dryer), item 4 (ability towash dishes/cooking utensils by hand), and item 6(ability to make beds), there was no statistically sig-nificant difference between the PLDS and controlgroups. By contrast, the FM group reported a statis-tically significantly greater amount of impairmentthan the controls for every task, and were signifi-cantly more impaired than PLDS patients in theirability to wash dishes (item 4), vacuum rugs (item 5),make beds (item 6), walk several blocks (item 7),visit friends and relatives (item 8), and do yard work(item 9). However, the PLDS subjects demonstrated astatistically significantly greater amount of impair-ment than the control group in physical functioning,and the content validity of this item of the FIQ issupported by the small amount of missing data. Be-cause a number of the items may be gender-biased, itremains uncertain whether the physical functioningscore of the FIQ in its current form is sufficientlysensitive for evaluating men with PLDS. However,only one man in the PLDS group omitted a possiblygender-biased item.

Our findings indicate that the modified version ofthe FIQ used in this study may be a useful tool in

measuring the impairment in physical functioning,global well-being, and symptom severity associatedwith PLDS. The FM subjects demonstrated greaterlevels of impairment than the PLDS patients, withstatistically significant differences seen in physicalimpairment, higher FIQ total scores, and the severityof muscle and joint pain. Only on item 20, whichmeasures depression, did the PLDS patients scorehigher than the FM patients, but the observed differ-ence was statistically not significant.

These results support the concept that PLDS issimilar to FM but is milder in its clinical manifesta-tions. However, the items added to our modifiedversion of the FIQ did illustrate some differencesbetween these patients. For example, while the FMpatients experienced a statistically significantlygreater amount of both muscle and joint pain thanthe PLDS patients, the PLDS subjects experiencedmore joint than muscle pain. The reason for thisdifference is unclear. On the other hand, the overallsimilarity of scores might reflect a similar basis fortheir symptoms, and the difference may be related tothe duration of these symptoms.

The performance on two items added to the FIQ(the interference with ADLs and the severity of mem-ory/concentration problems) showed no statisticallysignificant difference between the FM and PLDSgroups, although the FM subjects demonstratedmore impairment than PLDS subjects. The relativelygreater amount of difficulty experienced by FM pa-tients in performing ADLs was in keeping with theoverall higher levels of impairment reported by thesesubjects. While subjective symptom reports and ob-jective measures of neurocognitive function may beabnormal in Lyme disease (14) and in patients withPLDS (2,15), neurocognitive impairment is not a de-fining feature of FM, but abnormalities have beendescribed (16).

In analyzing the results of this study, two factorsmust be kept in mind. The first is the question ofconstruct validity of the FIQ in evaluating the phys-ical impairment experienced by PLDS patients. Todetermine this, the known-groups technique wasused (13). Contrasting the scores of the PLDS, FM,and healthy control groups that differed on the mea-sured attributes allowed us to show that the inter-group differences can be assessed with this instru-ment. It would also be interesting for futurelongitudinal studies to look at the issue of test–retestreliability for this instrument with the PLDS popu-lation and to help determine the stability of theinstrument to measure PLDS symptoms over time.This is being measured at present in a prospective

46 Fallon et al Vol. 12, No. 1, February 1999

study of patients with early Lyme disease at ourinstitution (17).

Second, it is important to bear in mind that theFIQ was not created with the intention of developinga diagnostic set of norms for patients with fibromy-algia, according to Burckhardt (Burckhardt CS: per-sonal communication). Rather, Burckhardt statedthat the FIQ was designed as an aid to clinical eval-uation for the purposes of assessing therapeutic in-terventions for fibromyalgia (9). Our results suggestthat this instrument in its current form can providethe same function for PLDS patients. It is anticipatedthat further clinical studies already in progress willhelp to clarify these issues and provide greater in-sight into the differences seen between FM andPLDS patients.

We thank Dr. Barbara Orlowski for assistance with statisticalanalysis and Dr. Lillie M. Shortridge-Baggett for assistance withthe preparation of the manuscript.

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