Suspecting combined immunodeficiency disorders (CID) in children with acute infections is the first step in diagnosing this group of disorders. Lymphopenia is one screening investigation for these disorders but it lacks specificity as it is often observed in acute infections. We observed in our study that persistent lymphopenia for age by 2 weeks after illness onset enhances its specificity. Subjecting these children with persistent lymphopenia by 2 weeks to other expensive diagnostic investigations can be a strategy to diagnose CID in resource-limited settings.
Arumugam et al. (2026) studied this question.