Optimal cutoffs for defining pain in multiple sclerosis

Aug 30 2012

By medwireNews Reporters

A US study has identified optimal cutoffs for the definition of pain among individuals with multiple sclerosis (MS).

Importantly, the empirically based cutoffs for classifying pain appear to be lower in patients with MS than individuals with other illnesses.

The researchers, led by Kevin Alschuler (University of Washington School of Medicine, Seattle), say the use of the cutoffs will help physicians make clinical decisions.

"Clinicians are encouraged to use a lower threshold for determining that a patient with MS is experiencing clinically significant pain relative to patients with other medical conditions," state the researchers in Pain Medicine.

Pain intensity is typically measured using numerical rating scales in many clinical settings. However, treatment guidelines, including those from the World Health Organization, rate pain as mild, moderate, or severe. With these descriptive rating scales, however, it is difficult to define pain easily so as to classify patients into one of the three categories.

As a result, it can be difficult to "determine when patients are experiencing the level of pain specified in treatment guidelines," note the researchers.

Surveys to assess pain were sent to 246 patients with MS. The participants confirmed they were currently experiencing pain and then rated their pain on a scale from 0 (no pain) to 10 (pain as bad as it could be).

Pain interference with general activity, mood, mobility, normal work, relationships, sleep, and social activities, among others, was assessed using the 12-item Brief Pain Inventory (BPI). Again, patients rated their pain interference on a scale of 0 (no interference) to 10 (completely interferes).

Results showed that the optimal classification scheme for mild pain was 0-2. For moderate and severe pain, the numerical classification scheme was 3-5 and 6-10, respectively. In the cohort of patients, 22.5% had mild pain, 43.6% had moderate pain, and 33.9% had severe pain.

When assessing the "worst pain" only, the optimal classification scheme for mild, moderate, and severe pain was 0-4, 5-7, and 8-10, respectively. In this setting, 52% had mild "worst" pain, 33.5% had moderate worst pain, and 14.4% had severe worst pain.

Compared with previously published studies of pain cutoffs in non-MS populations, the average pain cutoff was scored one full point lower in MS, suggesting that "clear, between-condition differences may exist that warrant using different cutoffs" in different clinical settings.

The researchers say the difference might be attributed to the sample population used, or the fact that MS patients have diffuse disease and experience pain in multiple locations.

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