Validation of the composite autonomic symptom scale 31 (COMPASS-31) in patients with and without small fiber polyneuropathy

Abstract

Background The recently developed composite autonomic symptom score-31 (COMPASS-31) is a questionnaire for assessing symptoms of dysautonomia. It was distilled from the well established autonomic symptom profile questionnaire. COMPASS-31 has not yet been externally validated. To do so, we assessed its psychometric properties and its convergent validity in patients with or without objective diagnosis of small fiber polyneuropathy (SFPN). Methods The internal validity and reliability of COMPASS-31 were assessed in participants with or without SFPN spanning the full autonomic symptoms severity. Convergent validity was assessed by comparing results of the COMPASS-31 and the gold standard autonomic function testing (AFT) which measures cardiovagal, adrenergic, and sudomotor functions. Additionally, relationships between COMPASS-31 and the Short Form McGill pain questionnaire, Short Form Health Survey and a 0-10 numeric pain scale were assessed. COMPASS-31 and all other questionnaires results were compared between patients with or without evidence of SFPN, objectively confirmed by distal-leg PGP9.5-immunolabeled skin biopsy. Results Among 66 participants (28 SFPN+, 38 SFPN-), COMPASS-31 total scores had excellent internal validity (Cronbach's α =0.919), test-retest reliability (rs=0.886; p<0.001), and good convergent validity (rs=0.474; p<0.001). COMPASS-31 scores differed between subjects with or without SFPN (Z=−3.296, p<0.001), and demonstrated fair diagnostic accuracy. Area under the receiver operating characteristic curve was 0.749 (P =0.01, 95% confidence interval 0.627-0.871). Conclusions COMPASS-31 has good psychometric properties in the population of patients being evaluated for SFPN and thus it might be useful as an initial screening tool for the more expensive SFPN objective tests.