Resuscitation. 2025 Oct 6:110851. doi: 10.1016/j.resuscitation.2025.110851. Online ahead of print.
ABSTRACT
BACKGROUND: Up to fifteen percent of out-of-hospital cardiac arrests (OHCAs) are precipitated by occult drug overdose – cases without history or evidence of drug use that are often attributed to a non-overdose cause. The NAloxone Cardiac ARrest Decision Instrument (NACARDI) was derived to help emergency medical service (EMS) providers rapidly identify patients at higher risk of occult opioid-associated (OA)-OHCAs during resuscitation. In this analysis we externally validate NACARDI in an independent cohort of OHCA patients.
METHODS: We conducted a retrospective validation using data from EMS-attended OHCA patients and coroner records in Ontario, Canada between 2020-2021. Inclusion criteria were age ≥18 years and OHCA death with a coroner record. Exclusion criteria were EMS-suspected drug overdose or known cause of the OHCA. NACARDI consists of two criteria: patient age and unwitnessed cardiac arrest. Two cut-offs for patient age were assessed for this validation: <50 years (NACARDI-50) and <60 years (NACARDI-60). The primary outcome was coroner adjudicated cause of death. We calculated screening characteristics and receiver operating characteristic (ROC) curves using standard formulae.
RESULTS: Of 2,904 OHCA cases without an obvious cause, 791 had coroner evaluations and 121 (15.3%) were adjudicated as occult OA-OHCA. NACARDI-60 had: sensitivity 82.6% (95%CI 74.9-88.4%), specificity 77.1% (95%CI 73.8-80.1%), negative predictive value 96.1% (95%CI 94.1-97.4%), and positive predictive value 39.4% (95%CI 33.6-45.5%). NACARDI-50 had: sensitivity 63.6% (95%CI 54.4-72.2%), specificity 89.3% (95%CI 86.7-91.5%), negative predictive value 93.2% (95%CI 90.9-95.0%), and positive predictive value 51.7% (95%CI 43.4-59.9%). ROC curves for both NACARDI-50 and NACARDI-60 demonstrated excellent discrimination for occult OA-OHCA.
CONCLUSION: In this external validation cohort, NACARDI had a sensitivity and specificity sufficiently high to aid in the real-time identification of occult OA-OHCA in the field. NACARDI has the potential to guide targeted interventions for OA-OHCA.
PMID:41062055 | DOI:10.1016/j.resuscitation.2025.110851
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