Testing relationships between clinical and non-clinical variables in xerostomia: a structural equation model of oral health-related quality of life.

OBJECTIVES

The aim of the study was to systematically test Wilson and Cleary's [Wilson IB, Cleary PD. JAMA 1995; 273: 59-65] conceptual model of the direct and mediated pathways between clinical and non-clinical variables in relation to the oral health-related quality of life (OHRQoL) of patients with xerostomia.

METHODS

We collected measures of clinical variables, self-reported symptoms, OHRQoL, global oral health perceptions and subjective well-being from 85 patients attending outpatient clinics.

RESULTS

Structural equation modelling indicated support for the dominant direct pathways between the main levels of the model; more severe clinical signs predicted worse patient reported symptoms; worse symptom perception was associated with a lower functional status as measured by OHRQoL; and lower OHRQoL predicted worse global oral health perceptions. There was no relationship between the final two levels of the model; global oral health perceptions and subjective well-being. Subjective well-being was associated instead with earlier non-adjacent levels; biological variables, symptoms and functional status. These pathways were both direct (salivary flow-well-being, functioning-well-being) and indirect (clinical signs-well being, symptom status-well-being). There were also indirect pathways; most notably, the impact of clinical variables on OHRQoL was mediated by patient reported symptom status.

CONCLUSIONS

The results support Wilson and Cleary's conceptual model of patient outcomes as applied to a chronic oral health condition and highlight the complexity of (inter)relationships between key clinical and non-clinical variables. Further conceptual development of the model is discussed, particularly the role of individual difference factors, and theoretical and methodological issues in OHRQoL research are highlighted.