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Background
Databases of electronic primary care records are widely used for research, but not currently as a source of national statistics on lifestyle issues such as smoking. There has been little contemporary research conducted into the quality of smoking data held within primary care, particularly since the introduction of the Quality and Outcomes Framework. This research is vital to assess the potential for using these large, longitudinal databases to monitor smoking trends.
Objectives
To compare smoking data recorded within The Health Improvement Network database (THIN) with the accepted “gold standard” for measuring smoking prevalence, to investigate the potential of using THIN data to track changes in smoking prevalence.
Methods
For 2000 to 2006, the annual prevalence of current, ex and never-smoking in THIN was determined, taking patients’ most recent smoking-related Read codes for that year as indicative of their smoking status. These figures were compared with the expected prevalence calculated using indirect standardisation based on age, sex and country-specific smoking rates from the corresponding General Household Survey (GHS).
Results
There was generally good agreement between recording of current smoking in THIN and the expected prevalence as predicted using GHS smoking rates. For example, in 2006 the GHS-predicted prevalence of current smoking in the THIN population was 23.4% for men (women 20.7%), with 22.6% of men (19.8% women) actually being recorded as current smokers in their medical records. The recording of ex and never-smoking within THIN was less complete—for men the recorded prevalence of both ex and never smoking was approximately 10 percentage points lower than would be expected using GHS rates, and for women 5 percentage points lower. 17.4% of men and 8.0% of women in THIN in 2006 had no smoking status recorded in their electronic medical records.
Conclusions
These results suggest that primary care medical records within THIN can be used to identify current smokers possibly with enough accuracy for use in monitoring smoking prevalence nationally. However, recording of ex and never-smokers is less complete.