To validate the objective monitoring of ambulatory activity as an outcome measure for rheumatoid arthritis (RA).
We have compared ambulatory activity to a range of currently favoured outcome measures, ranging from subjective opinions to X-ray damage, in a population of 93 RA sufferers.
Correlations were stronger with measures of joint damage and disability, and less strong with measures of disease activity. Sensitivity to change was good. Three different interventions were compared for the quantity of the response, and the results agree with clinical experience, with steroid injection of the knee and use of non-steroidal anti-inflammatory drugs (NSAIDs) having a similar response and the provision of surgical shoes producing a more modest increase in ambulation.
The measurement of ambulatory activity has validity for RA assessment. It provides different but related data to the currently used measures. It is objective, relevant, quantifiable and of unlimited scale. It could be used to quantify interventions aimed at increasing ambulation, in carefully constructed studies.