Development and validation of a patient self-assessed questionnaire on satisfaction with communication of the multiple sclerosis diagnosis

Method: A multiple sclerosis expert panel generated questionnaire items from the Doctor's Interpersonal Skills Questionnaire, literature review, and interviews with neurology inpatients. The resulting 19-item Comunicazione medico-paziente nella Sclerosi Multipla (COSM) was pilot tested/debriefed on seven patients with multiple sclerosis and administered to 80 patients newly diagnosed with multiple sclerosis. The resulting revised 20-item version (COSM-R) was debriefed on five patients with multiple sclerosis, field tested/debriefed on multiple sclerosis patients, and field tested on 105 patients newly diagnosed with multiple sclerosis participating in a clinical trial on an information aid. The hypothesized monofactorial structure of COSM-R section 2 was tested on the latter two groups. Results: The questionnaire was well accepted. Scaling assumptions were satisfactory in terms of score distributions, item-total correlations and internal consistency. Factor analysis confirmed section 2's monofactorial structure, which was also test-retest reliable (intraclass correlation coefficient [ICC] 0.73; 95% CI 0.54-0.85). Section 1 had only fair test-retest reliability (ICC 0.45; 95% CI 0.12-0.69), and three items had 8-21% missed responses. Conclusions: COSM-R is a brief, easy-to-interpret MS-specific questionnaire for use as a health care indicator.