L.D. Roorda

Mind the MIC: large variation among populations and methods

OBJECTIVE There is no consensus on the best method to determine the minimal important change (MIC) of patient-reported outcomes. Recent publications recommend the use of multiple methods. Our aim was to assess whether different methods lead to consistent values for the MIC. STUDY DESIGN AND SETTING We used two commonly used anchor-based methods and three commonly used distribution-based methods to determine the MIC of the subscales: pain and physical functioning of the Western Ontario and McMaster University Osteoarthritis Index questionnaire in five different studies involving patients with hip or knee complaints. We repeated the anchor-based methods using relative change scores, to adjust for baseline scores. RESULTS We found large variation in MIC values by the same method across studies and across different methods within studies. We consider it unlikely that this variation can be explained by differences between disease groups, disease severity, or lengths of follow-up. The variation persisted when using relative change scores. It was not possible to conclude whether this variation is because of true differences in MIC values between populations or to conceptual and methodological problems of the MIC methods. CONCLUSION To better disentangle these two possible explanations, the MIC methodology should be improved and standardized. In the meantime, caution is needed when interpreting and using published MIC values.

Proprioception in knee osteoarthritis: a narrative review

OBJECTIVE To give an overview of the literature on knee proprioception in knee osteoarthritis (OA) patients. METHOD A literature search was performed and reviewed using the narrative approach. RESULTS (1) Three presumed functions of knee proprioception have been described in the literature: protection against excessive movements, stabilization during static postures, and coordination of movements. (2) Proprioceptive accuracy can be measured in different ways; correlations between these methods are low. (3) Proprioceptive accuracy in knee OA patients seems to be impaired when compared to age-matched healthy controls. Unilateral knee OA patients may have impaired proprioceptive accuracy in both knees. (4) Causes of impaired proprioceptive accuracy in knee OA remain unknown. (5) There is currently no evidence for a role of impaired proprioceptive accuracy in the onset or progression of radiographic osteoarthritis (ROA). (6) Impaired proprioceptive accuracy could be a risk factor for progression (but not for onset) of both knee pain and activity limitations in knee OA patients. (7) Exercise therapy seems to be effective in improving proprioceptive accuracy in knee OA patients. CONCLUSIONS Recent literature has shown that proprioceptive accuracy may play an important role in knee OA. However, this role needs to be further clarified. A new measurement protocol for knee proprioception needs to be developed. Systematic reviews focusing on the relationship between impaired proprioceptive accuracy, knee pain and activity limitations and on the effect of interventions (in particular exercise therapy) on proprioceptive accuracy in knee OA are required. Future studies focusing on causes of impaired proprioceptive accuracy in knee OA patients are also needed, taking into account that also the non-symptomatic knee may have proprioceptive impairments. Such future studies may also provide knowledge of mechanism underlying the impact of impaired proprioceptive accuracy on knee pain and activity limitations.

CHECK (Cohort Hip and Cohort Knee): similarities and differences with the Osteoarthritis Initiative

Objective: To describe the osteoarthritis study population of CHECK (Cohort Hip and Cohort Knee) in comparison with relevant selections of the study population of the Osteoarthritis Initiative (OAI) based on clinical status and radiographic parameters. Methods: In The Netherlands a prospective 10-year follow-up study was initiated by the Dutch Arthritis Association on participants with early osteoarthritis-related complaints of hip and/or knee: CHECK. In parallel in the USA an observational 4-year follow-up study, the OAI, was started by the National Institutes of Health, on patients with or at risk of symptomatic knee osteoarthritis. For comparison with CHECK, the entire cohort and a subgroup of individuals excluding those with exclusively hip pain were compared with relevant subpopulations of the OAI. Results: At baseline, CHECK included 1002 participants with in general similar characteristics as described for the OAI. However, significantly fewer individuals in CHECK had radiographic knee osteoarthritis at baseline when compared with the OAI (p<0.001). In contrast, at baseline, the CHECK cohort reported higher scores on pain, stiffness and functional disability (Western Ontario and McMaster osteoarthritis index) when compared with the OAI (all p<0.001). These differences were supported by physical health status in contrast to mental health (Short Form 36/12) was at baseline significantly worse for the CHECK participants (p<0.001). Conclusion: Although both cohorts focus on the early phase of osteoarthritis, they differ significantly with respect to structural (radiographic) and clinical (health status) characteristics, CHECK expectedly representing participants in an even earlier phase of disease.

Prevalence and course of forefoot impairments and walking disability in the first eight years of rheumatoid arthritis

OBJECTIVE To evaluate the prevalence and 8-year course of forefoot impairments and walking disability in patients with rheumatoid arthritis (RA). METHODS A total of 848 patients with recent-onset RA from 1995 through the present were included. The patients were assessed annually. Pain and swelling of the metatarsophalangeal (MTP) joints, erosions and joint space narrowing of the MTP joints and first interphalangeal joints, and the Health Assessment Questionnaire walking subscale were analyzed using descriptive and correlational techniques. RESULTS Pain and swelling of > or = 1 MTP joint was present in 70% of patients at baseline, decreasing to approximately 40-50% after 2 years. The forefoot erosion score was > or = 1 in 19% of the patients at baseline, and the prevalence of forefoot erosion increased to approximately 60% after 8 years, during which the mean forefoot erosion score increased from 1.3 to 7.9. At least mild walking disability was present in 57% of patients at baseline, stabilizing at approximately 40% after 1 year. CONCLUSION The prevalence rates for pain and swelling of the MTP joints and walking disability are initially high and then stabilize, but the prevalence and severity of forefoot joint damage increase during an 8-year course of RA. The findings of this study quantitatively emphasize the importance of forefoot involvement in patients with RA.

Nonparametric IRT analysis of Quality-of-Life Scales and its application to the World Health Organization Quality-of-Life Scale (WHOQOL-Bref)

BackgroundThis study investigates the usefulness of the nonparametric monotone homogeneity model for evaluating and constructing Health-Related Quality-of-Life Scales consisting of polytomous items, and compares it to the often-used parametric graded response model.MethodsThe nonparametric monotone homogeneity model is a general model of which all known parametric models for polytomous items are special cases. Merits, drawbacks, and possibilities of nonparametric and parametric models and available software are discussed. Particular attention is given to the monotone homogeneity model (also known as the Mokken model), and the often-used parametric graded response model.ResultsData from the WHOQOL-Bref were analyzed using both the monotone homogeneity model and the graded response model. The monotone homogeneity model analysis yielded unidimensional scales for each content domain. Scalability coefficients further showed that some items have limited scalability with respect to the other items in the same scale. The parametric IRT analyses lead to the rejection of some of the items.ConclusionsThe nonparametric monotone homogeneity model is highly suited for data analysis in a health-related quality-of-life context, and the parametric graded response model may add interesting features to measurement provided the model fits the data well.

Improving the Action Research Arm test: a unidimensional hierarchical scale

Background: The Action Research Arm (ARA) test is a performance test of upper extremity motor function which consists of 19 items divided into four hierarchical subtests. This multidimensionality has not yet been tested empirically. Objective: To investigate the dimensionality of the ARA test. Design: Cross-sectional study involving a sample of 63 chronic stroke patients. Methods: A Mokken scale analysis was performed. Results: The Mokken scale analysis revealed one strong unidimensional scale containing all 19 items, of which the scalability coefficient H was 0.79, while H per item ranged from 0.69 to 0.86. The reliability coefficient rho equalled 0.98, indicating a very high internal consistency. A subset of 15 out of 19 items showed an invariant hierarchical item-ordering. Conclusion: The ARA test is a unidimensional scale. The use of subtests, as proposed in the original description of the instrument, is not supported by the present findings. The 15-item scale presented here can be used for adaptive testing, i.e. using only a selected subset of items based on prior knowledge about the patients abilities, thus minimizing testing time.

Identification of phenotypes with different clinical outcomes in knee osteoarthritis: data from the Osteoarthritis Initiative

To identify subgroups or phenotypes of knee osteoarthritis (OA) patients based on similarities of clinically relevant patient characteristics, and to compare clinical outcomes of these phenotypes.

Measuring Functional Limitations in Rising and Sitting Down: Development of a Questionnaire

OBJECTIVE Develop and test a self-administered questionnaire that measures perceived and actual functional limitations in rising and sitting down. SETTING Private practices for physical therapy and outpatient clinics of hospitals and rehabilitation centers. PATIENTS 345 outpatients (43% male, aged 14 to 92 years) with different grades of functional limitations and different types of lower extremity orthopedic or rheumatologic disorders. METHODS The Questionnaire Rising and Sitting Down (QR&S) was developed on the basis of a literature review and careful operationalization of functional limitations. Five dimensions concerning different objects (high chair, low chair, toilet, bed, and car) and one global dimension were postulated to be contained in the instrument. Mokken scale analysis was used to test the postulated dimensions (scalability coefficient H). Furthermore, robustness with respect to patient characteristics was determined, as well as intratest reliability (reliability coefficient Rho), test-retest reliability (intraclass correlation coefficient [ICC]), content validity (coverage of operationalized aspects), and construct validity (testing of seven hypotheses). RESULTS Mokken scale analysis confirmed the existence of 5 object dimensions (H = .53-.59). However, two global dimensions were found (H = .50-.54). The resulting hierarchical scales, consisting of subsets of the 32 final QR&S items, are robust and measure functional limitations in a reliable (Rho .77-.91; ICC .72-.90) and valid (3 out of 4 aspects covered, 2 hypotheses rejected for 3 out of 7 scales) manner. CONCLUSION The QR&S is a reliable and valid self-administered questionnaire. It consists of hierarchical scales and measures perceived and actual functional limitations in rising and sitting down.

Association of lower muscle strength with self-reported knee instability in osteoarthritis of the knee: Results from the Amsterdam Osteoarthritis Cohort

To determine whether muscle strength, proprioceptive accuracy, and laxity are associated with self‐reported knee instability in a large cohort of knee osteoarthritis (OA) patients, and to investigate whether muscle strength may compensate for impairment in proprioceptive accuracy or laxity, in order to maintain knee stability.

Three trajectories of activity limitations in early symptomatic knee osteoarthritis: a 5-year follow-up study

Objectives Knee osteoarthritis (OA) is a leading cause of activity limitations. The knee OA population is likely to consist of subgroups. The aim of the present study was to identify homogeneous subgroups with distinct trajectories of activity limitations in patients with early symptomatic knee OA and to describe characteristics of these subgroups. Methods Follow-up data over a period of 5 years of 697 participants with early symptomatic knee OA from the Cohort Hip and Cohort Knee (CHECK) were used. Activity limitations were measured yearly with the Western Ontario and McMaster Universities Osteoarthritis Index. Latent class growth analyses identified homogeneous subgroups with distinct trajectories of activity limitations. Multivariable regression analyses examined differences in characteristics between the subgroups. Results Three subgroups were identified. Participants in Subgroup 1 (‘good outcome’; n=330) developed or displayed slight activity limitations over time. Participants in Subgroup 2 (‘moderate outcome’; n=257) developed or displayed moderate activity limitations over time. Participants in subgroup 3 (‘poor outcome’; n=110) developed or displayed severe activity limitations over time. Compared with the ‘good outcome’ subgroup, the ‘moderate outcome’ and ‘poor outcome’ subgroups were characterised by: younger age, higher body mass index, greater pain, bony tenderness, reduced knee flexion, hip pain, osteophytosis, ≥3 comorbidities, lower vitality or avoidance of activities. Conclusions Based on the 5-year course of activity limitations, we identified homogeneous subgroups of knee OA patients with good, moderate or poor outcome. Characteristics of these subgroups were consistent with existing knowledge on prognostic factors regarding activity limitations, which supports the validity of this classification.