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Can short PROMs support valid factor-based sub-scores? Example of COMQ-12 in chronic otitis media.

Published version
Peer-reviewed

Type

Article

Change log

Authors

Haggard, Mark 
Spencer, Helen 
Arsovic, Nenad 
Sipetic Grujicic, Sandra 

Abstract

PURPOSE: Interpretable factor solutions for questionnaire instruments are typically taken as justification for use of factor-based sub-scores. They can indeed articulate content and construct validities of a total and components but do not guarantee criterion validity for clinical application. Our previous documentation of basic psychometric characteristics for a 12-item patient-reported outcome measure in adult chronic otitis media (COMQ-12) justified next appraising criterion validity of sub-scores. METHODS: On 246 cases at 1st clinic visit, we compared various classes of factor solution, concentrating on the best-fitting 3-factor ones as widely supported. Clinical data offered two independent measures as external criteria: binaural hearing (audiometric thresholds measured via audiometry) for evaluating 'Hearing' sub-score, and oto-microscopic findings for the 'Ear discharge symptoms' sub-score. As criterion for the total, and for semi-generic 'Activities/healthcare' sub-score, the generic Short Form-36 item set offered a widely used multi-item criterion measure. RESULTS: Factor model fit and parsimony again favoured a 3-factor solution for COMQ-12; however insufficient item support and the dominant 1st principal component of variation made sub-scoring problematic. The best solution was bi-factor, from which only the weighted total score met the declared convergent validity standard of r = 0.50. Two of the more specific sub-scores ('Ear discharge symptoms' and 'Hearing') correlated poorly with clinical findings and weighted binaural hearing thresholds. CONCLUSION: The COMQ-12 total is acceptably content-valid for general clinical purposes, but the small item set, reflecting excessive pressure for brevity in clinical application, does not well support three criterion-valid factor-based scores. This distinction should be made explicit, and profile sub-scoring discouraged until good convergent and furthermore divergent criterion validities are shown.

Description

Keywords

Adult, Ambulatory Care, Chronic Disease, Documentation, Hearing, Humans, Otitis Media

Journal Title

PLoS One

Conference Name

Journal ISSN

1932-6203
1932-6203

Volume Title

17

Publisher

Public Library of Science (PLoS)