Validation of Suicide and Self-harm records in the Clinical Practice Research Datalink

Aims The UK's Clinical Practice Research Datalink (CPRD) is increasingly used to investigate suicide- related adverse drug reactions. No studies have comprehensively validated the recording of suicide and non-fatal self-harm in the CPRD. We validated GP's recording of these outcomes using linked Office for National Statistics (ONS) mortality and hospital episode statistics (HES) admission data. Methods We identified cases of suicide and self-harm recorded using appropriate Read codes in the CPRD between 1998 and 2010 in patients aged ≥ 15 years. Suicides were defined as patients with Read codes for suicide recorded within 95 days of their death. ICD codes were used to identify suicides/hospital admissions for self-harm in the linked ONS and HES datasets. We compared CPRD derived cases/incidence of suicide and self-harm with those identified from linked ONS mortality and HES data, national suicide incidence rates and published self-harm incidence data. Results Only 26.1% (n=590) of the ‘true’ (ONS-confirmed) suicides were identified using Read codes. Furthermore, only 55.5% of Read code identified suicides were confirmed as suicide by the ONS data. 68.4% of HES-identified cases of self–harm were identified in the CPRD using Read codes. CPRD self-harm rates based on Read codes had similar age and sex distributions to rates observed in self-harm hospital registers although rates were underestimated in all age groups. Conclusions CPRD recording of suicide using Read codes is unreliable, with significant inaccuracy (over and under-reporting). Future CPRD suicide studies should use linked ONS mortality data. The under-reporting of self-harm appears to be less marked.