Objective: To study universal primer 16S rRNA gene polymerase chain reaction (PCR) for diagnosis of blood culture-positive neonatal sepsis before and after starting antibiotic drug therapy.
Design: Prospective study of diagnostic tests.
Setting: Level III neonatal intensive care unit. Patients Neonates with a fresh episode of clinically suspected sepsis were enrolled; those with major malformations, life expectancy less than 12 hours, or contaminated blood cultures were excluded.
Interventions: Before starting antibiotic drug therapy, PCR (0 hour), blood culture, and sepsis screening (complete blood cell counts, micro-erythrocyte sedimentation rate, and C-reactive protein level) were performed. The PCR was repeated 12, 24, and 48 hours after starting antibiotic drug therapy.
Main outcome measures: The primary outcomes were the sensitivity and specificity of 0-hour PCR for diagnosing blood culture-positive sepsis, and the secondary outcome was the proportion of 0-hour PCR-positive patients who remained positive after antibiotic drug therapy.
Results: Of 306 patients evaluated, 242 were included (mean [SD] gestation, 32.2 [3.1] weeks; and mean [SD] birth weight, 1529.2 [597.2] g). Blood culture was positive in 52 patients and 0-hour PCR in 57. The sensitivity, specificity, positive and negative predictive values, and positive and negative likelihood ratios of PCR were 96.2%, 96.3%, 87.7%, 98.8%, 26.1, and 0.04, respectively. Two patients were blood culture positive but 0-hour PCR negative, whereas 7 were 0-hour PCR positive but blood culture negative. Of the 0-hour PCR-positive patients, 7 remained positive at 12 hours and none at 24 and 48 hours after starting antibiotic drug therapy. In 0-hour PCR-positive patients, no predictors of positive 12-hour PCR were identified.
Conclusion: Universal primer PCR can accurately diagnose neonatal sepsis before but not after antibiotic drugs are given.