What Is the Smallest Change in Arm Function That Patients With MS Find Meaningful?

What change in the ability to walk or in upper-limb function do patients with multiple sclerosis (MS) find important? There are not many ways to measure such a change.

The ability to walk without help and upper extremity function (UEF) are domains that are assessed in patients with MS, but among the measures available, only one, the Arm Function in Multiple Sclerosis Quiestionnaire (AMSQ), uses patient-reported outcomes. In a study published in Multiple Sclerosis Journal, researchers sought to determine the minimal clinically important difference (MCID), which defines the smallest change that the patient would find important or meaningful.

“Determining an MCID of a [patient-reported outcome measure] is important because a given change on the score generally does not have an obvious clinical importance to the clinician,” the authors explained.

A total of 223 patients who were treated with fampridine were recruited at the VU Medical Center in Amsterdam. More than half (56.5%) had a progressive disease type, the median disease duration was 11.4 years, and the median Expanded Disability Status Scale score 6.0. Fampridine is supposed to improve various motor functions, generally within 2 weeks of treatment. The patients completed the AMSQ before treatment and during a follow-up visit that took place at least 2 weeks after treatment.

The AMSQ includes 31 items related to hand and arm functioning, and patients assign a number to each item. The final score ranges from 31 (indicating no limitations) to 186 (indicating no function). The researchers calculated the change in the score by substracting the follow-up AMSQ score from the baseline score. A positive score indicated an improvement in UEF.

Then, the researchers use a global perceived effect (GPE) score that addressed change in UEF and was determined by the physician during the follow-up visit taking place at least 2 weeks after treatment. The GPE scores were divided into either “improved” or “unchanged.” They determined the AMSQ score that produced the greatest combined sensitivity and specificity through a received operating characteristic curve. This was the MCID.

The MCID value for the AMSQ was 15 points, meaning a 15-point change in AMSQ score, which has a range of 31 to 186, was the smallest change in function that patients found meaningful.

“Future studies should investigate reproducibility of this finding with similar and other methods, in a cohort with extensive assessment of different domains of UEF,” the authors concluded.

Reference

van Munster CE, Kaya L, Obura M, Kalkers NF, Uitdehaag BM. Minimal clinically important difference of improvement on the Arm Function in Multiple Sclerosis Questionnaire (AMSQ) [published online January 18, 2019]. Mult Scler. doi: 10.1177/1352458518823489.