Completeness and diagnostic validity of recording acute myocardial infarction events in primary care, hospital care, disease registry, and national mortality records: cohort study

Abstract

Objective: To determine the completeness and diagnostic validity of myocardial infarction recording across four national health record sources in primary care, hospital care, a disease registry, and mortality register.

Design: Cohort study.

Participants: 21 482 patients with acute myocardial infarction in England between January 2003 and March 2009, identified in four prospectively collected, linked electronic health record sources: Clinical Practice Research Datalink (primary care data), Hospital Episode Statistics (hospital admissions), the disease registry MINAP (Myocardial Ischaemia National Audit Project), and the Office for National Statistics mortality register (cause specific mortality data).

Setting: One country (England) with one health system (the National Health Service).

Main outcome measures: Recording of acute myocardial infarction, incidence, all cause mortality within one year of acute myocardial infarction, and diagnostic validity of acute myocardial infarction compared with electrocardiographic and troponin findings in the disease registry (gold standard).

Results: Risk factors and non-cardiovascular coexisting conditions were similar across patients identified in primary care, hospital admission, and registry sources. Immediate all cause mortality was highest among patients with acute myocardial infarction recorded in primary care, which (unlike hospital admission and disease registry sources) included patients who did not reach hospital, but at one year mortality rates in cohorts from each source were similar. 5561 (31.0%) patients with non-fatal acute myocardial infarction were recorded in all three sources and 11 482 (63.9%) in at least two sources. The crude incidence of acute myocardial infarction was underestimated by 25-50% using one source compared with using all three sources. Compared with acute myocardial infarction defined in the disease registry, the positive predictive value of acute myocardial infarction recorded in primary care was 92.2% (95% confidence interval 91.6% to 92.8%) and in hospital admissions was 91.5% (90.8% to 92.1%).

Conclusion: Each data source missed a substantial proportion (25-50%) of myocardial infarction events. Failure to use linked electronic health records from primary care, hospital care, disease registry, and death certificates may lead to biased estimates of the incidence and outcome of myocardial infarction.

Trial registration: NCT01569139 clinicaltrials.gov.

Fig 1 Crude incidence of acute fatal and non-fatal myocardial infarction estimated using different combinations of data from primary care (Clinical Practice Research Datalink), hospital admissions (Hospital Episode Statistics), disease registry (MINAP, Myocardial Ischaemia National Audit Project), and death registry (Office for National Statistics)

Fig 2 Kaplan Meier curves showing all cause mortality, stratified by record source in 20 819 patients: Clinical Practice Research Datalink (n=15 819), Hospital Episode Statistics (n=13 831), Myocardial Ischaemia National Audit Project (MINAP) (n=10 351). Myocardial infarctions recorded by the Office for National Statistics are not shown as they are by definition fatal on the date of myocardial infarction

Fig 3 Number and percentage of records recorded in primary care (Clinical Practice Research Datalink), hospital care (Hospital Episode Statistics), and disease registry (Myocardial Ischaemia National Audit Project) for non-fatal myocardial infarction across the three sources (n=17 964 patients)