Validity of out-of-hospital and in-hospital cardiac arrest algorithms in the Danish National Patient Registry.

AIMS

Cardiac arrest is registered in the Danish National Patient Registry (DNPR) with the International Classification of Diseases 10 revision code I46. However, it does not distinguish between out-of-hospital cardiac arrest (OHCA) and in-hospital cardiac arrest (IHCA). We validated an algorithm to identify cardiac arrest subtypes (out-of-hospital vs. in-hospital).

METHODS

From Aarhus University Hospital, Denmark, we sampled patients with a primary or secondary cardiac arrest discharge diagnosis during 2019-2023. The algorithm categorized these patients as OHCA if they (1) only had a single department course during their hospitalization or (2) had multiple department courses during their hospitalization but were discharged with a cardiac arrest diagnosis from the first department course. The algorithm categorized the remaining patients as IHCA. We randomly sampled 200 patients with algorithm-based OHCA ( = 100) and IHCA ( = 100). Using medical record review as the reference, we calculated positive predictive values (PPVs) with 95% confidence intervals (CIs).

RESULTS

Cardiac arrest was confirmed in 192 of 200 cases, yielding a PPV for cardiac arrest overall of 96% (95% CI: 92-98%). The PPV was 87% (95% CI: 79-92%) for OHCA and 61% (95% CI: 51-70%) for IHCA. The results were robust in age and sex strata.

CONCLUSIONS

The validity of a cardiac arrest diagnosis in the DNPR was overall high. The algorithm to distinguish cardiac arrest subtypes showed a high PPV for OHCA but a poor PPV for IHCA.