Diagnosing paediatric myocarditis: what really matters.

Objective: Paediatric myocarditis has remained a diagnostic challenge. We aim to identify distinct characteristics and derive a scoring system that will trigger further investigations to be performed among paediatric patients presenting to the emergency department (ED) with clinically suspected myocarditis.

Design: We performed an age-matched case-control study of children seen in a large tertiary institution. Cases and controls were patients less than 16 years' old who presented to the ED over a 10-year period from Jan 2001 to Dec 2010. Cases were identified with a final discharge or postmortem diagnosis of acute myocarditis. Controls were those who presented to the ED in the same period and were initially diagnosed with acute myocarditis, but who were later found to have other diagnoses. We compared their vital signs, presenting symptoms, physical examination findings, electrocardiogram and chest radiograph findings.

Results: Based on domain-specific stepwise conditional logistic regression analyses, five characteristics were found to be potentially discriminating: respiratory distress, poor perfusion, hypotension, an abnormal chest radiograph and any electrocardiogram abnormalities. Satisfactory discrimination was attained using these five parameters. The estimated area under receiver operating characteristic curve was 90% (95% CI 0.83 to 0.97). A cut-off score of 3 would give a positive likelihood ratio of 13 (95% CI 3.31 to 51.06) and a negative likelihood ratio of 0.35 (95% CI 0.22 to 0.55).

Conclusions: A cut-off risk score of 3, though not yet validated, may be potentially useful in future to trigger further investigations for children with suspected myocarditis. It allows for the appropriate use of resources, while minimising on misdiagnosis.