The Reliable Change Index: A Novel Approach to Estimate Osteoarthritis Progression

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The Reliable Change Index is an effective method to identify change in joint space width, removing many apparent changes that are likely due to measurement error.
The Reliable Change Index is an effective method to identify change in joint space width, removing many apparent changes that are likely due to measurement error.

The Reliable Change (RCI) Index is an effective method for identifying changes in joint space width in clinical and research settings and has proven useful for estimating the progression of osteoarthritis (OA), according to the results of the 3-year international Strontium Ranelate Efficacy in Knee Osteoarthritis trial (SEKOIA) published in Arthritis Care & Research.

The investigators sought to examine the utility of the RCI as a novel approach to estimating OA progression. Data from patients who were randomly assigned to the placebo group of the SEKOIA study were used. Patients were recruited into the trial between 2006 and 2008 from 98 centers in 18 countries.

A total of 392 women and 167 men with knee OA, diagnosed using the American College of Rheumatology criteria, were assessed annually. At study entry, the participants had a mean disease duration of just over 4 years, and the men generally had longer disease duration compared with the women. The RCI was used to determine whether the magnitude of change in joint space width on radiographs was likely to be true or due to measurement error. The mean joint space width at baseline was 3.51 mm, which decreased to 3.15 mm by the conclusion of the study. The minimum joint space width at baseline was 0.65 mm, which decreased to 0.38 mm over the course of the study. The largest individual reduction in joint space width over the study course was 3.34 mm.

Between consecutive years, 57% to 69% of participants experienced an apparent (change <0) decrease in joint space width, whereas 31% to 43% of participants reported annual changes that were indicative of improvement in joint space width. The RCI identified decreases in joint space width in only 6.0% of participants between baseline and 1 year and in 4.5% of participants in the remaining years of the study. The apparent increases in joint space width were nearly eliminated between baseline and year 1. Moreover, between years 1 and 2, only 1.3% of the participants experienced a statistically significant increase in joint space width, and this rate decreased to 0.9% between years 2 and 3.

The investigators concluded that applying the RCI in knee OA disease progression studies should facilitate an enhanced understanding of the progression of joint space narrowing. If the benefits of the RCI are confirmed in other patient populations, this would likely assist in research efforts, lead to better management of patients with OA, and help improve quality of life in these individuals.

Please see original article for a full list of disclosures.

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Reference

Parsons C, Judge A, Leyland K, et al; SEKOIA Study Group. Novel approach to estimate osteoarthritis progression – use of the reliable change index in the evaluation of joint space loss [published online May 9, 2018]. Arthritis Care Res (Hoboken). doi:10.1002/acr.23596

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