Minimal detectable change for mobility and patient-reported tools in people with osteoarthritis awaiting arthroplasty

• Published in: BMC musculoskeletal disorders 2014-07, Vol.15 (1), p.235-235, Article 235
• Main Authors: Naylor, Justine M, Hayen, Andrew, Davidson, Edward, Hackett, Danella, Harris, Ian A, Kamalasena, Gihan, Mittal, Rajat
• Format: Article
• Language: English
• Subjects: Activities of daily living; Aged; Arthritis; Arthroplasty; Arthroplasty, Replacement, Hip; Arthroplasty, Replacement, Knee; Biomechanical Phenomena; Care and treatment; Clinical medicine; Diagnosis; Disability Evaluation; Exercise Test; Female; Health aspects; Hip Joint - physiopathology; Hip Joint - surgery; Humans; Joint surgery; Knee Joint - physiopathology; Knee Joint - surgery; Male; Medical research; Medicine, Experimental; Middle Aged; Musculoskeletal diseases; New South Wales; Older people; Osteoarthritis; Osteoarthritis, Hip - diagnosis; Osteoarthritis, Hip - physiopathology; Osteoarthritis, Hip - surgery; Osteoarthritis, Knee - diagnosis; Osteoarthritis, Knee - physiopathology; Osteoarthritis, Knee - surgery; Pain; Pain Measurement; Patients; Predictive Value of Tests; Reproducibility of Results; Severity of Illness Index; Surgery; Time Factors; Waiting Lists
• ISSN: 1471-2474; 1471-2474
• DOI: 10.1186/1471-2474-15-235

Thoughtful use of assessment tools to monitor disease requires an understanding of clinimetric properties. These properties are often under-reported and, thus, potentially overlooked in the clinic. This study aimed to determine the minimal detectable change (MDC) and coefficient of variation per cent (CV%) for tools commonly used to assess the symptomatic and functional severity of knee and hip osteoarthritis. We performed a test-retest study on 136 people awaiting knee or hip arthroplasty at one of two hospitals. The MDC95 (the range over which the difference [change] for 95% of patients is expected to lie) and the coefficient of variation per cent (CV%) for the visual analogue scale (VAS) for joint pain, the six-minute walk test (6MWT), the timed up-and-go (TUG) test, the Knee Injury and Osteoarthritis Outcome Score (KOOS) and the Hip Disability and Osteoarthritis Outcome Score (HOOS) subscales were calculated. Knee cohort (n = 75) - The MDC95 and CV% values were as follows: VAS 2.8 cm, 15%; 6MWT 79 m, 8%; TUG +/-36.7%, 13%; KOOS pain 20.2, 19%; KOOS symptoms 24.1, 22%; KOOS activities of daily living 20.8, 17%; KOOS quality of life 26.6, 44. Hip cohort (n = 61) - The MDC95 and CV% values were as follows: VAS 3.3 cm, 17%; 6MWT 81.5 m, 9%; TUG +/-44.6%, 16%; HOOS pain 21.6, 22%; HOOS symptoms 22.7, 19%; HOOS activities of daily living 17.7, 17%; HOOS quality of life 24.4, 43%. Distinguishing real change from error is difficult in people with severe osteoarthritis. The 6MWT demonstrates the smallest measurement error amongst a range of tools commonly used to assess disease severity, thus, has the capacity to detect the smallest real change above measurement error in everyday clinical practice.