The Health of the Nation Outcome Scales: Validating Factorial Structure and Invariance Across Two Health Services

Abstract

Objective: The Health of the Nation Outcome Scale (HoNOS) was developed in the mid-1990s as an inclusive and comprehensive instrument to measure patient outcomes in four main factors: behaviour, impairment, symptoms and social problems. This paper attempts to investigate whether similar health services rate the HoNOS with equivalent psychometric calibration. Method: The purpose of this study was to test for invariant construct interpretation of the instrument across two equivalent health services, using simultaneous confirmatory factor analysis. Results: Although the four-factor model of the HoNOS was confirmed, structural non-invariance occurred, casting doubt on the equivalent interpretability and generalisability of the instrument across similar heath services. Conclusions: Over-inclusiveness, lack of specificity and questionable independence of observations may have contributed to the non-invariant factor structure between the two health services. Such results shed some doubt on the ability of the HoNOS and like observational instruments to provide equivalent comparisons between health services.