Burden of out-of-hospital cardiac arrest in Karachi, Pakistan: Estimation through the capture-recapture method.

Objective: To assess the application of capture-recapture method as a potential strategy to estimate the incidence of out-of-hospital cardiac arrest. Methods: This cross-sectional study was carried out from January to April 2013 in Karachi and comprised three public general hospitals, one public cardiac hospital, one private general hospital and two ambulance services. Two-sample capture-recapture method was used: first capture was through cardiac arrest data from two major emergency medical services and second capture was from the five teaching hospitals. Records from the hospitals and ambulance services were compared on 7 variables; name, age, gender, date and time of arrest, cause of arrest and destination hospital. Matched and unmatched cases were used in the equation to estimate the incidence of out-of-hospital cardiac arrest. Results: Of the 630 out-of-hospital cardiac arrest cases reported, 191(30.3%) related to the emergency medical services records and 439(69.7%) to hospital records. The capture-recapture identified only 9(1.4%) matched cases even with the least restrictive criteria and estimated the annual out-of-hospital cardiac arrest incidence as 166/100,000 population (95% confidence interval: 142.9 to 189.6). Conclusion: Capture-recapture method could be a potential alternative for providing population level data in the absence of organised health information systems.