Background State-attainment criteria in OA are increasingly used in adjudicating individual patient outcomes following therapeutic interventions. However, factors influencing published values of PASS criteria in OA, have yet to be fully evaluated.
Objectives To assess the effect of global vs domain-specific symptom acceptability statements, on PASS estimates in knee OA.
Methods In this cross-sectional study, patients with knee OA, under specialist care, completed the WOMAC NRS4.1 OA Index. They also completed a questionnaire designed to elicit the acceptability of their current symptomatic state (SS). One question asked about overall acceptability of the SS, while three other questions asked respectively about the specific acceptability of the patient's pain, stiffness and physical function. The 75th percentile of WOMAC scores in those patients indicating their current SS as being acceptable, defined the PASS (75) value.
Results 47 patients with knee OA (M:F =17:30; Median Age =63.0 years (41,80); Median Disease Duration =48.0 months (4,240); Kellgren-Lawrence Grades – I =2, II =17, III =27; Median WOMAC scores: pain =19.00 (0,68); stiffness =20.00 (0,70); function =21.76 (0.00,74.71). While most individuals were consistent in their global and domain-specific reporting of SS, one patient reported acceptability at the global level but not at stiffness or function domain levels, and 1-4 patients reported acceptability at the domain level but unacceptability at the global level. Median WOMAC scores for those regarding their SS unacceptable, were approximately double those regarding their SS acceptable.
The acceptability statements resulted in PASS (75) estimates as follows: Global acceptability statements - pain = 26.00, stiffness = 26.25, function = 29.01; Domain-specific acceptability statements - pain = 23.50, stiffness = 25.00, function = 29.01. Several patients who regarded their SS as unacceptable reported WOMAC domain scores lower than the PASS threshold - Pain = 7, stiffness and function = 9 patients. Conversely, several patients who rated their global health state as acceptable reported SS scores higher than the PASS threshold - pain, stiffness and function =6 patients.
Conclusions 1) PASS estimates were similar whether calculated using global or domain-specific acceptability statements. 2) Some patients who regarded their global health state as unacceptable had better scores than others who regarded their health state acceptable. 3) The PASS values estimated for this group of Australian patients were lower than collective values recently published from a multinational study (1). 4) Caution should be exercised in generalising PASS estimates, particularly to cultures, nationalities, demographics and outcome measures not encompassed by previous studies. 5) Further PASS research involving larger numbers of patients from various cultures, ethnicities and countries is recommended. 6) The determinants of PASS require more extensive evaluation.
Bellamy N et al. Development of Multinational Definitions of Minimal Clinically Important Improvement and Patient Acceptable Symptomatic State in Osteoarthritis. Arthritis Care and Research. 2014 [Accepted article]. doi 10.1002/acr.22538.
Disclosure of Interest None declared