Procalcitonin, at a low threshold (≥0.25 ng/ml), has been shown to be useful in directing the use of antibiotics in adults with pneumonia [3], and a recent meta-analysis concludes that procalcitonin may offer some advantages over C-reactive protein (CRP) for discriminating bacterial from nonbacterial infections [4]. The gene discussed is CRP; the disease is susceptibility to pneumonia measurement.