Role of C reactive protein and procalcitonin in the diagnosis of lower respiratory tract infection in children in the outpatient setting

### What you need to know A previously healthy and fully vaccinated (including 13-valent pneumococcal conjugate vaccine) 22 month old boy is brought to the emergency department because of a 12 hour history of high fever (up to 40°C). He had had low grade fever, runny nose, cough, and decreased oral intake for the past two days. On examination, he did not look severely ill but was febrile (38.3°C). His respiratory rate was 45 breaths/minute (normal range 25-40 breaths/min at 18-24 months old), heart rate was 140 beats/minute (normal range 98-135 beats/min at 18-24 months), and blood oxygen level was 95%. Although breath sounds were not decreased, some bibasilar crackles were noted on chest auscultation. A chest x ray was interpreted as having bilateral peribronchial infiltrates and haziness in the right lower lobe. To aide their decision whether to initiate antibiotic therapy, clinicians requested blood tests, which revealed a white blood cell count of 22.5×109/L (60.0% neutrophils), a CRP of 30 mg/L (normal <5 mg/L), and a PCT of 0.25 μg/L (normal <0.5 μg/L). Lower respiratory tract infections (LRTIs) in childhood are commonly of viral aetiology. Distinguishing viral from bacterial LRTI in children—and thus appropriately …