Psychometric characteristics of the chronic Otitis media questionnaire 12 (COMQ – 12): stability of factor structure and replicability shown by the Serbian version

BACKGROUND Recently, demand for and supply of short-form patient-reported outcome measures (PROMs) have risen throughout the world healthcare. Our contribution to meeting that demand has been translating and culturally adapting the Chronic Otitis Media Questionnaire-12 (COMQ-12) for adults into Serbian and enhancing its psychometric base on the relatively large Serbian COM caseload. Chronic otitis media can seriously affect quality of life progressively and in long-term, and it remains the major source of hearing problems in the developing world. METHODS The translated questionnaire was given twice to 60 adult patients with chronic otitis media of three types (inactive, active mucosal and active squamous disease) and to 60 healthy volunteers. Both patients and volunteers also filled the generic Short-Form 36 questionnaire (SF-36). Conventional statistical procedures were used in strategically driven development of scoring. Additionally, item responses were scaled by linear mapping against the provisional total score. Generalizability, detailed factor interpretation and supportability of scores were criteria, for the best compromise factor solution. RESULTS Test-retest reliability was very high (0.924 to 0.989, depending on score). The a priori content dimensions of the questionnaire were strongly supported by 3-factor exploratory and confirmatory factor analyses for content validity, separating (i) ear symptoms from (ii) hearing problems, from (iii) daily activity restriction plus healthcare uptake. The 3-factor structure was furthermore highly stable on replication. The very large effect sizes when contrasting patients with healthy volunteers, and active with inactive disease established construct validity for the total score. A strong association with disease activity and a moderate one with generic health-related quality of life (HRQoL), the SF-36, supported construct validity for two of three factors extracted (ear symptoms, and impact on daily activities plus healthcare uptake). CONCLUSIONS Given the minimal psychometric work to date on COMQ-12, this interim sample with 120 data points adds materially to knowledge of its reliability, several forms of validity and the feasibility of profile sub-scores to supplement total scores. The good psychometric properties shown for COMQ-12 justify both its routine clinical use and acquisition of the necessarily larger sample for generality, score optimisation and the evaluation of responsiveness.