Generalisability of The Health Improvement Network (THIN) database: demographics, chronic disease prevalence and mortality rates.

INTRODUCTION The degree of generalisability of patient databases to the general population is important for interpreting database research. This report describes the representativeness of The Health Improvement Network (THIN), a UK primary care database, of the UK population. METHODS Demographics, deprivation (Townsend), Quality and Outcomes Framework (QOF) condition prevalence and deaths from THIN were compared with national statistical and QOF 2006/2007 data. RESULTS Demographics were similar although THIN contained fewer people aged under 25 years. Condition prevalence was comparable, e.g. 3.5% diabetes prevalence in THIN, 3.7% nationally. More THIN patients lived in the most affluent areas (23.5% in THIN, 20% nationally). Between 1990 and 2009, standardised mortality ratio ranged from 0.81 (95% CI: 0.39-1.49; 1990) to 0.93 (95% CI: 0.48-1.64; 1995). Adjusting for demographics/deprivation, the 2006 THIN death rate was 9.08/1000 population close to the national death rate of 9.4/1000 population. CONCLUSION THIN is generalisable to the UK for demographics, major condition prevalence and death rates adjusted for demographics and deprivation.