Validation of a health screening questionnaire for primary care using Rasch models

BACKGROUND: Health inequality is on the rise due to various social and individual factors. While preventive health checks (PHC) aim to counteract health inequality, there is robust evidence against the use of PHC in general practice. It is unknown which factors can identify persons who will benefit from preventive interventions that are more beneficial than harmful. Hence, valid screening instruments are needed. METHODS: The aim of this study was to assess the psychometric properties of a screening questionnaire (SQ-33), which targets vulnerable persons in primary care practice who can benefit from preventive consultations. Survey data were acquired from 20 primary care clinical practices in the Northern Region of Jutland, Denmark. Respondents were 2056 persons between 20 and 44 years old who, for any reason, consulted their family doctor. The psychometric properties of the SQ-33 were assessed using Rasch item response modelling. Follow-up analysis was performed on a subsample of 364 persons one year subsequent to initial inclusion, in order to assess responsiveness and predictive validity using a general health anchor item. RESULTS: Twenty-three of the SQ-33 items in four subscales fit a Graphical loglinear Rasch model (GLLRM) at baseline and follow-up, thus confirming the scaling properties. The modified 23-item version (HSQ-23) revealed superior responsiveness and predictive validity compared with the SQ-33. CONCLUSIONS: The Health Screening Questionnaire (HSQ-23) was shown to possess adequate psychometric properties and responsiveness and can thus be used as an outcome measure in preventive intervention studies. Future study should address whether the HSQ-23 successfully identifies patients who will benefit from PHC consultations.