T. Uhlig, E. A. Haavardsholm and T. K. Kvien

Rheumatology 2006;45:454 458 Advance Access publication 15 November 2005 Comparison of the Health Assessment Questionnaire (HAQ) and the modified HAQ (MHAQ) in patients with rheumatoid arthritis T. Uhlig, E. A. Haavardsholm and T. K. Kvien doi:10.1093/rheumatology/kei181 Objectives. Physical disability in patients with rheumatoid arthritis (RA) is often assessed by questionnaires. We compared the Health Assessment Questionnaire (HAQ) with the modified HAQ (MHAQ) in a cohort of RA patients across various levels of disability, and examined correlations with other measures of physical function. Methods. Patients with RA (n ¼ 182) completed self-report questionnaires assessing functional capacity. Instruments included the MHAQ and HAQ completed separately, as well as SF-36 and the Arthritis Impact Measurement Scales (AIMS). Scores from unadjusted and adjusted HAQ were compared with MHAQ at various disability levels. Results. A clear ceiling effect with aggregation of normal scores for physical function was observed for MHAQ (23%) and HAQ (12%), but not for SF-36 (4%) or AIMS (5%). The correlations between adjusted/unadjusted HAQ and MHAQ scores were 0.85/0.88. A discrepancy in HAQ and MHAQ scores was observed in patients with high levels of disability, especially when MHAQ was compared with the adjusted final HAQ score. Adjustment of HAQ by aids or help increased the final score by an average of 0.15, and both adjusted and unadjusted HAQ scores were numerically clearly higher (mean 0.45 and 0.30, respectively) than the MHAQ score. Conclusion. The present findings indicate that MHAQ and HAQ may be applicable as measures of physical capacity in RA patients, but clinicians and researchers should select the appropriate instrument for the setting, and be aware of differences in scores, especially at different disability levels. KEY WORDS: Rheumatoid arthritis, Disability, Outcome, Questionnaire, HAQ, MHAQ, AIMS2, SF-36, Quality of life. Health status measures in rheumatic diseases have achieved growing attention. Patient-reported physical functioning with questionnaires is one of the core outcome measures in randomized clinical trials as well as in observational longitudinal studies of rheumatoid arthritis (RA) [1], and assessment of physical disability has been recommended for daily practice [2]. The introduction of the Stanford Health Assessment Questionnaire (HAQ) [3] more than 20 yr ago greatly facilitated the clinical assessment of patients capacity to perform activities of daily life (ADL), and the HAQ has become a widely accepted instrument. A shortened version of the HAQ, the Modified Health Assessment Questionnaire (MHAQ) [4], reduced the number of items from 20 in the original HAQ to eight, and improved the feasibility in clinical practice when screening patients. Both the MHAQ and the HAQ are sensitive to change in clinical trials [5], but the HAQ has been more efficient than the MHAQ in detecting treatment change [6]. The HAQ and the MHAQ are both useful in studies on prognosis [7, 8]. The scoring procedures are different, as the HAQ includes questions on devices or aid, leading to a possible increase in the final score. This effect of adjustment on the final HAQ score is not clear [9]. Data collection using the HAQ has revealed major differences in scores. The ceiling problem of both HAQ and MHAQ has been addressed and has recently led to the development of the MDHAQ [10] and the HAQ-II [11]. We have little knowledge about comparisons with separately completed HAQ and MHAQ addressing different levels of physical function in patients with RA, including also other measures of physical disability or other dimensions in health. Thus, our objective was to compare HAQ and MHAQ scores in a cohort of RA patients across various levels of disability and to examine correlations with other measures of physical function or health outcomes. Materials and methods A total of 182 RA patients completed self-reported functional assessments in an observational study on the course of RA [12]. All but three patients (n ¼ 179) filled in questionnaires on physical disability and were included in the study. Mean age (S.D.) was 55.8 (12.9) yr, 74% were females, mean (S.D.) disease duration was 7.2 (1.2) yr and 68% were rheumatoid factor positive. Questionnaires assessed health status and demographic variables. Functional capacity in patients was assessed according to the Health Assessment Questionnaire (HAQ) [3], the MHAQ [4], SF-36 [13] and the Arthritis Impact Measurement Scales (AIMS) [14]. The MHAQ and HAQ were completed separately, and both questionnaires were presented with other instruments in between to reduce recall bias. The HAQ queries the ability to perform 20 activities of daily living [15] with four response categories [without any difficulty (score 0), with some difficulty (score 1), with much difficulty (score 2), not being able to do (score 3)]. The 20 activities are classified into eight categories with two or three activities each. Department of Rheumatology, Diakonhjemmet Hospital, Box 23 Vinderen, N-0319 Oslo, Norway. Submitted 8 July 2005; revised version accepted 30 September 2005. Correspondence to: T. Uhlig, National Resource Center for Rehabilitation in Rheumatology, Department of Rheumatology, Diakonhjemmet Hospital, Box 23 Vinderen, N-0319 Oslo, Norway. E-mail: till.uhlig@nrrk.no 454 ß The Author 2005. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. 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HAQ and MHAQ in RA 455 A score is then assigned to each of the eight categories based on the highest score of any activity within the category. Patients are also asked about the use of aids and devices, and if they need help from another person for activities in any of the eight categories. If the category score is lower than 2, it is increased to 2 in any category in which the patient uses a device or help from another person, so that underlying disability is more accurately represented [16]. The total HAQ score is the mean of the scores for the eight categories, and has been validated in a number of languages including Swedish, which is very similar to the Norwegian language [17]. An alternative scoring method ignores adjustment of the scores, expressing the sum HAQ as the average of the eight categories without considering devices or help [16]. The MHAQ [4], as a modification of the HAQ, keeps one question from each of the eight categories in the HAQ, thus reducing the number of items to eight. No adjustment of scores is permitted. The MHAQ score is calculated as the mean of the scores for each activity. The SF-36 [13, 18] is a widely used generic quality of life instrument, and one of eight scales measures physical function. AIMS originally contained nine scales, one of these being the physical scale. Applying the three-component model of AIMS [19], six scales were combined for the AIMS physical component; the anxiety and depression scales were combined for the psychological component. Fatigue and pain (100 mm visual analogue scales) and patient global assessment of disease activity (verbal rating scale 1 5) were used as additional self-reported instruments for health status. Other measures included joint examinations assessing 66 swollen and 68 tender joint counts [20] as well as the Ritchie articular index [21]. Laboratory markers of inflammation were erythrocyte sedimentation rate (ESR) and C-reactive protein. Hand grip strength [22] was measured and recorded as the mean between right and left hand. Finally, conventional hand radiographs were obtained and scored according to the Sharp method modified by van der Heijde et al. [23]. Mean scores for individual items and categories from HAQ and MHAQ were tabulated and compared across different levels of disability using Bland Altman plots [24]. Differences between HAQ or adjusted HAQ and MHAQ were plotted against the average of the two scores. The mean differences between HAQ and MHAQ were calculated and plotted as a line. Limits of agreement, using the mean difference 1.96 S.D. of the differences, were computed and plotted as lines. The value for R 2 of the line of best fit is presented in the legend of the Bland Altman diagrams. Correlations of scores between the different variables were expressed by Pearson correlation coefficients. Cumulative probability curves were drawn with MHAQ and HAQ values as a function of cumulative percentages of patients. The regional ethical committee approved the study. Statistical analyses were performed with SPSS 12.0. P values <0.05 were considered as statistically significant. Results Correlation coefficients between HAQ, unadjusted HAQ, MHAQ, AIMS physical and the SF-36 physical function scale ranged from 0.71 to 0.85 (Table 1). Mean (S.D.) scores were for HAQ 0.91 (0.65), adjusted HAQ 0.76 (0.58), MHAQ 0.46 (0.42), AIMS physical 2.16 (1.53) and the SF-36 physical functioning scale 59.1 (24.4). Table 2 presents results for all 20 HAQ and eight MHAQ items from the separately answered questionnaires. Only minor differences were observed between scores for the eight questions in the MHAQ and for the identical questions in the HAQ questionnaire. The mean values with standard deviations for the eight HAQ categories of functioning and for MHAQ for 179 patients completing MHAQ and HAQ are displayed in Table 3, including scores with and without adjustment. The adjusted HAQ value for each category was consistently higher than the unadjusted value, which again was higher than the value for the MHAQ component. TABLE 1. Pearson correlations coefficients between instruments measuring physical function in RA patients (n ¼ 179, all P<0.01) HAQ not adjusted MHAQ TABLE 2. Mean crude scores (S.D.) for responses to individual questions in the HAQ and MHAQ (n ¼ 179) in RA patients AIMS physical component SF physical HAQ adjusted 0.96 0.85 0.82 0.79 HAQ not adjusted 0.88 0.82 0.78 MHAQ 0.80 0.71 AIMS physical 0.80 Questions: Are you able to... HAQ (0 3) MHAQ (0 3) a Dressing Dress yourself, including tying shoelaces and doing buttons? 0.61 (0.61) 0.51 (0.52) Shampoo your hair? 0.49 (0.67) Rising Stand up from an armless straight chair? 0.45 (0.65) Get in and out of bed? 0.38 (0.56) 0.30 (0.48) Eating Cut your meat? 0.71 (0.70) Lift a full cup or glass to your mouth? 0.39 (0.57) 0.34 (0.52) Open a new milk carton? 0.77 (0.76) Walking Walk outdoors on flat ground? 0.34 (0.57) 0.39 (0.63) Climb up five steps? 0.34 (0.58) Hygiene Wash and dry your entire body? 0.63 (0.73) 0.61 (0.71) Take a tub bath? 0.93 (0.97) Get on and off the toilet? 0.15 (0.41) Reach Reach and get down a 5-pound object from just above your head? 0.57 (0.71) Bend down to pick up clothing from the floor? 0.39 (0.57) 0.40 (0.59) Grip Open car doors? 0.38 (0.57) Open jars which have been previously opened? 0.47 (0.65) Turn taps on and off? 0.58 (0.67) 0.62 (0.73) Usual activities Run errands and shop? 0.54 (0.73) Get in and out of a car? 0.46 (0.58) 0.49 (0.56) Do chores such as vacuuming or yard work? 1.09 (0.87) a Recoded from the original range 1 4 to range 0 3.

456 T. Uhlig et al. Adjustment of HAQ by aids or help increased the final score by an average of 0.15, and both adjusted and unadjusted HAQ scores were numerically clearly higher (mean 0.45 and 0.30, respectively) than the MHAQ score. Table 4 presents as percentiles the distribution of scores for HAQ, HAQ without adjustment, MHAQ, AIMS physical and SF-36 physical functioning, demonstrating considerable ceiling effects (aggregation of good scores), especially for MHAQ but also for HAQ. Scores indicating optimal functioning were reported for SF-36 physical in 4%, for AIMS physical in 5%, for unadjusted and adjusted HAQ in 12% and for MHAQ in 23% (data not shown). The table can be used to find for a median MHAQ score the corresponding adjusted (unadjusted) HAQ score. For example, at the 80th percentile, the HAQ score was 0.75 (unadjusted 0.5) units higher than the corresponding MHAQ score (Table 4). The HAQ and MHAQ were also compared at different levels of physical functioning using Bland Altman plots (Fig. 1a and b), demonstrating that most differences were within the limits of agreement, but there was a discrepancy in HAQ and MHAQ scores in patients with high levels of disability, especially when MHAQ was compared with the adjusted final HAQ score (Fig. 1a). Individual scores for adjusted and unadjusted HAQ and for MHAQ were plotted against the cumulative percentages of patients. The area between the curves demonstrates the overall differences in the measurement of physical disability by the different instruments (Fig. 2). Finally, HAQ and MHAQ sum scores were compared with clinical measures including other health dimensions and clinical outcome measures (Table 5). Generally, no major differences were observed for most comparisons, but correlation coefficients were somewhat lower when comparing joint counts and radiographic damage with MHAQ than with HAQ. TABLE 3. Mean scores (S.D.) for HAQ categories (crude scores and after adjustment of scores for devices or aids) and MHAQ (n ¼ 179) TABLE 4. Percentiles for HAQ, HAQ without adjustment, MHAQ, AIMS physical and SF-36 physical scale (n ¼ 179) Percentile Number HAQ (adjusted) HAQ (adjusted) HAQ (without adjustment) MHAQ a SF-36 physical AIMS physical 10 0 0 0 25 0.4 20 0.25 0.25 0 35 0.8 30 0.5 0.375 0.125 45 1.2 40 0.625 0.5 0.25 55 1.6 50 0.875 0.625 0.375 60 2.0 60 1.125 0.875 0.5 70 2.4 70 1.25 1.0 0.625 75 2.7 80 1.5 1.25 0.75 85 3.4 90 1.875 1.5 1.0 90 4.1 100 2.75 2.5 1.75 100 7.5 a Recoded from original range 1 4 to range 0 3. HAQ (without adjustment) MHAQ a Dressing 179 0.83 (0.79) 0.70 (0.68) 0.51 (0.52) Rising 179 0.64 (0.75) 0.54 (0.66) 0.30 (0.48) Eating 179 0.88 (0.80) 0.88 (0.80) 0.34 (0.52) Walking 178 0.58 (0.78) 0.47 (0.65) 0.39 (0.63) Hygiene 178 1.20 () 1.02 (0.96) 0.61 (0.71) Reach 178 0.80 (0.85) 0.65 (0.72) 0.40 (0.59) Grip 178 1.12 (0.94) 0.71 (0.72) 0.62 (0.73) Usual activities 178 1.26 (0.92) 1.11 (0.86) 0.49 (0.56) Disability score 178 0.91 (0.65) 0.76 (0.58) 0.46 (0.42) a Recoded from original range 1 4 to range 0 3. Discussion This study shows that HAQ and MHAQ scores are strongly correlated, but also that there are major numerical differences in the scores, especially at high disability levels. Thus, the disability score is dependent on the scoring method used, and highly dependent on whether HAQ or MHAQ are being used. This is potentially relevant for clinicians, because physical disability measured with both HAQ and MHAQ are strong prognostic markers for mortality in RA, stronger than global disease severity, and other clinical, laboratory and radiographic features using either absolute values or quartiles [7, 8, 25]. So far no conversion factor from a MHAQ to a HAQ score has been suggested [26]. The regression line in Fig. 1a and b as (a) (b) Difference adjusted HAQ - MHAQ Difference unadjusted HAQ - MHAQ 2.00 0 0.5 1 1.5 2 2.5 Disability level (HAQ + MHAQ)/2 2.00 2.50 Disability level (HAQ + MHAQ)/2 FIG. 1. Agreement between HAQ and MHAQ displayed in a Bland Altman diagram, including lines for mean difference and upper and lower limits of agreement. (a) HAQ score adjusted for devices or for aid by another person (r 2 ¼ 0.4362). (b) HAQ score without adjustment (r 2 ¼ 0.3431).

HAQ and MHAQ in RA 457 well as the values in Table 4 give some clue to the relationship between the HAQ and the MHAQ score. In patients in the lowest quartile of disability, the HAQ score is only slightly higher, in the second quartile about 0.5 units higher, and in patients with the highest disability about 1.0 unit higher. These differences are also of interest because the HAQ score has been converted to utility to be used in economic models [27]. Patients in this study had a moderate disease disability with considerable ceiling effects in the HAQ and MHAQ scores, not only for total scores but also for individual items and HAQ components. For intervention studies in RA it is important to use instruments that minimize ceiling effects so that they may Disability 3.00 2.75 2.50 2.25 2.00 1.75 1.25 0.75 0.25 0.01 0.13 0.25 0.37 0.62 0.74 0.87 0.99 Cumulative probability MHAQ HAQ adjusted HAQ unadjusted FIG. 2. Cumulative probability plots for adjusted HAQ, unadjusted HAQ and MHAQ scores. MHAQ scores are recoded to 0 3. TABLE 5. Bivariate relationship between HAQ and MHAQ with other clinical health status and outcome measures* HAQ adjusted HAQ unadjusted MHAQ SF-36 physical function 0.79 0.78 0.71 SF-36 role physical 0.48 0.44 SF-36 pain 0.60 0.62 0.63 SF-36 general health 0.48 0.44 SF-36 vitality 0.34 0.39 0.34 SF-36 social function 0.49 0.54 0.53 SF-36 mental role 0.35 0.38 0.36 SF-36 mental health 0.36 0.40 0.39 Swollen joints (66) 0.43 0.39 0.33 Tender joints (68) 0.43 0.41 0.30 Ritchie score 0.61 0.63 0.58 C-reactive protein 0.32 0.28 0.29 ESR 0.20** 0.17*** 0.14**** AIMS psychological 0.33 0.37 0.39 Modified Sharp score 0.25** 0.20*** 0.13**** Grip strength 0.55 0.52 0.42 Fatigue (100 mm VAS) 0.42 0.40 0.38 Patient global assessment 0.28 0.28 0.27 Pain (100 mm VAS) 0.58 0.58 0.62 *Pearson correlation coefficients, all P<1 unless indicated: **P<0.01, ***P<0.05, ****not significant. demonstrate potential improvements of health status. Almost 20 yr after the introduction of the HAQ, the multidimensional Health Assessment Questionnaire (MD-HAQ) [10] has been introduced, also addressing pain, fatigue, global status and morning stiffness. The MD-HAQ takes account of improved medical strategies with improved physical function in RA by including more difficult tasks ( Can you walk two miles ). This decreases the magnitude of the ceiling effect present in the HAQ and the MHAQ [28]. Improved access to devices during recent decades may have led to increased disability scores measured by the HAQ, thus overestimating physical disability in individual patients. Differences between adjusted and unadjusted HAQ scores were of minor importance in this study compared with discrepancies between HAQ and MHAQ, as the discrepancy was still present when unadjusted HAQ scores were used (Fig. 1b). In rheumatology out-patient settings questionnaires could virtually be given to all patients for disability screening [2]. Short questionnaires like the MHAQ may in such settings outweigh poorer performance compared with the HAQ in states with high physical disability. The same may be the case in population surveys. In patients with high disease severity, the MHAQ may underestimate the magnitude of disability [29]. In a previous report, we found that physical function measured by both AIMS2 and MHAQ had distributions skewed to the left and were insensitive to low disability levels. Both instruments had, however, similar responsiveness when patient-assessed global disease activity was used as an external indicator of change in health status [30, 31]. The categorical nature of the HAQ scores has to be kept in mind. For example, a 0.5 unit improvement in HAQ from baseline 2.0 does not correspond to an improvement of 0.5 with an initial HAQ score of 1.0. Furthermore, the HAQ and MHAQ were originally designed to be used as total scores. However, recently the components of the HAQ have also been examined and some differences were found when exploring their associations with clinical variables [32]. The recently published HAQ-II [11] has deleted some activities from the original HAQ, such as Shampoo your hair and Do yard work which were problematic, thus increasing the reliability and validity of the instrument. The present findings indicate that MHAQ and HAQ may be applied for the assessment of physical function in RA patients. Generally there is large agreement between the different questionnaires in the HAQ family (HAQ, MHAQ, MDHAQ, HAQ-II), but both clinicians and researchers should select the appropriate instrument dependent on its purpose, being aware of differences between instruments regarding disability levels. In population surveys with a low prevalence of physical disability, the MHAQ may suffice as a screening instrument, and a trade-off can be made to achieve scores in a large number of individuals. The HAQ demonstrates a higher discriminative ability in patient groups with higher disability, such as in hospital settings or drug trials. When the HAQ is used as an outcome measure or in economic models, it should always be reported whether scores are adjusted due to aids or the use of technical devices. Rheumatology Key messages A discrepancy in HAQ and MHAQ scores is present in patients with high levels of disability, especially when MHAQ is compared with the adjusted final HAQ score. Both HAQ and MHAQ may be useful when screening patients for physical function, and the choice of the appropriate instrument depends on the setting where it is used.

458 T. Uhlig et al. Acknowledgements We thank Petter Mowinckel for statistical advice. The authors have declared no conflicts of interest. References 1. Wolfe F, Lassere M, van der Heijde D et al. Preliminary core set of domains and reporting requirements for longitudinal observational studies in rheumatology. J Rheumatol 1999;26:484 9. 2. Wolfe F, Pincus T. Listening to the patient: a practical guide to self-report questionnaires in clinical care. Arthritis Rheum 1999; 42:1797 808. 3. Fries J, Spitz PW, Young DY. The dimensions of health outcomes: the health assessment questionnaire, disability and pain scales. J Rheumatol 1982;9:789 93. 4. Pincus T, Summey JA, Soraci SA Jr, Wallston KA, Hummon NP. Assessment of patient satisfaction in activities of daily living using a modified Stanford health assessment questionnaire. Arthritis Rheum 1983;26:1346 53. 5. Strand V, Cohen S, Schiff M et al. Treatment of active rheumatoid arthritis with leflunomide compared with placebo and methotrexate. Leflunomide Rheumatoid Arthritis Investigators Group. Arch Intern Med 1999;159:2542 50. 6. Wolfe F. Which HAQ is best? A comparison of the HAQ, MHAQ and RA-HAQ, a difficult 8 item HAQ (DHAQ), and a rescored 20 item HAQ (HAQ20): analyses in 2,491 rheumatoid arthritis patients following leflunomide initiation. J Rheumatol 2001;28:982 9. 7. Wolfe F, Michaud K, Gefeller O, Choi HK. Predicting mortality in patients with rheumatoid arthritis. Arthritis Rheum 2003:48;1530 42. 8. Callahan LF, Pincus T, Huston JW3rd, Brooks RH, Nance EP Jr, Kaye JJ. Measures of activity and damage in rheumatoid arthritis: depiction of changes and prediction of mortality over five years. Arthritis Care Res 1997;10:381 94. 9. Serrano MA, Beltran Fabregat J, Olmedo Garzon J. Should the MHAQ ever be used? Ann Rheum Dis 1996;55:271 2. 10. Pincus T, Swearingen C, Wolfe F. Toward a multidimensional Health Assessment Questionnaire (MDHAQ): assessment of advanced activities of daily living and psychological status in the patientfriendly health assessment questionnaire format. Arthritis Rheum 1999;42:2220 30. 11. Wolfe F, Michaud K, Pincus T. Development and validation of the health assessment questionnaire II: a revised version of the health assessment questionnaire. Arthritis Rheum 2004;50:3296 305. 12. Uhlig T, Smedstad LM, Vaglum P, Moum T, Gerard N, Kvien TK. The course of rheumatoid arthritis and predictors of psychological, physical and radiographic outcome after 5 years of follow-up. Rheumatology 2000;39:732 41. 13. Ware JE Jr, Sherbourne CD. The MOS 36-item short-form health survey (SF-36). I. Conceptual framework and item selection. Med Care 1992;30:473 83. 14. Meenan RF, Gertman PM, Mason JH. Measuring health status in arthritis. The Arthritis Impact Measurement Scales. Arthritis Rheum 1980;23;146 52. 15. Fries JF, Spitz P, Kraines RG, Holman HR. Measurement of patient outcome in arthritis. Arthritis Rheum 1980;23:137 45. 16. Bruce B, Fries JF. The Stanford Health Assessment Questionnaire: a review of its history, issues, progress, and documentation. J Rheumatol 2003;30:167 78. 17. Ekdahl C, Eberhardt K, Andersson SI, Svensson B. Assessing disability in patients with rheumatoid arthritis. Use of a Swedish version of Stanford Health Assessment Questionnaire. Scand J Rheumatol 1988;17:263 71. 18. Kvien TK, Kaasa S, Smedstad LM. Performance of the Norwegian SF-36 Health Survey in patients with rheumatoid arthritis. II. A comparison of the SF-36 with disease- specific measures. J Clin Epidemiol 1998;51:1077 86. 19. Brown JH, Kazis LE, Spitz PW, Gertman P, Fries JF, Meenan RF. The dimensions of health outcomes: a cross-validated examination of health status measurement. Am J Public Health 1984; 74:159 61. 20. Felson DT, Anderson JJ, Boers M et al. The American College of Rheumatology preliminary core set of disease activity measures for rheumatoid arthritis clinical trials. The Committee on Outcome Measures in Rheumatoid Arthritis Clinical Trials. Arthritis Rheum 1993;36:729 40. 21. Ritchie DM, Boyle JA, McInnes JM et al. Clinical studies with an articular index for the assessment of joint tenderness in patients with rheumatoid arthritis. Q J Med 1968;37:393 406. 22. Nordenskio ld UM, Grimby G. Grip force in patients with rheumatoid arthritis and fibromyalgia and in healthy subjects. A study with the Grippit instrument. Scand J Rheumatol 1993;22:14 19. 23. van der Heijde DM, van Riel PL, Nuver-Zwart IH, Gribnau FW, van de Putte LB. Effects of hydroxychloroquine and sulphasalazine on progression of joint damage in rheumatoid arthritis. Lancet 1989;1:1036 8. 24. Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986;1:307 10. 25. Wolfe F, Kleinheksel SM, Cathey MA, Hawley DJ, Spitz PW, Fries JF. The clinical value of the Stanford Health Assessment Questionnaire Functional Disability Index in patients with rheumatoid arthritis. J Rheumatol 1988;15;1480 8. 26. Wolfe F. The psychometrics of functional status questionnaires: room for improvement. J Rheumatol 2002;29:865 8. 27. Kobelt G, Jonsson L, Lindgren P, Young A, Eberhardt K. Modeling the progression of rheumatoid arthritis: a two-country model to estimate costs and consequences of rheumatoid arthritis. Arthritis Rheum 2002;46:2310 19. 28. Stucki G, Stucki S, Bruhlmann P, Michel BA. Ceiling effects of the Health Assessment Questionnaire and its modified version in some ambulatory rheumatoid arthritis patients. Ann Rheum Dis 1995;54:461 5. 29. Lubeck DP. Health-related quality of life measurements and studies in rheumatoid arthritis. Am J Manag Care 2002;8:811 20. 30. Haavardsholm EA, Kvien TK, Uhlig T, Smedstad LM, Guillemin F. A comparison of agreement and sensitivity to change between AIMS2 and a short form of AIMS2 (AIMS2-SF) in more than 1,000 rheumatoid arthritis patients. J Rheumatol 2000;27: 2810 16. 31. Hagen KB, Smedstad LM, Uhlig T, Kvien TK. The responsiveness of health status measures in patients with rheumatoid arthritis: comparison of disease-specific and generic instruments. J Rheumatol 1999;26:1474 80. 32. Häkkinen A, Kautiainen H, Hannonen P, Ylinen J, Arkela-Kautiainen M, Sokka T. Pain and joint mobility explain individual subdimensions of the health assessment questionnaire (HAQ) disability index in patients with rheumatoid arthritis. Ann Rheum Dis 2005;64:59 63.