Diagnostic Performance of the "Lab-Score" in Predicting Severe and Invasive Bacterial Infections in Well-Appearing Young Febrile Infants.

BACKGROUND AND OBJECTIVES: The "Lab-score" combining C-reactive protein, procalcitonin and urine dipstick results has recently been derived and validated as an accurate tool for predicting severe bacterial infections (SBI) in children with fever without source (FWS). We aimed to assess the "Lab-score" usefulness in predicting SBI, and especially invasive bacterial infections (IBI) in well-appearing infants <3 months with FWS. METHODS: A multicenter retrospective study was carried in 7 pediatric emergency departments in Spain and Italy. An SBI was defined as isolation of a bacterial pathogen from urine, blood, cerebrospinal fluid, or stools; an IBI as isolation of a bacterial pathogen from blood or cerebrospinal fluid. The diagnostic characteristics of the "Lab-score" for detection of SBI and IBI were calculated. RESULTS: An SBI was diagnosed in 287 (28.3%) of 1012 patients and an IBI in 23 (2%) of 1098. The positive and negative likelihood ratios of a score ≥3 for SBI prediction were 10.2 (95%CI 9.5-10.9) and 0.5 (95%CI 0.5-0.5) respectively. The AUC was 0.83 (95%CI 0.80-0.86). The same diagnostic accuracy measures for identification of IBI were 4.3 (95%CI 4-4.6), 0.4 (95%CI 0.3-0.5) and 0.85 (95%CI 0.76-0.94) respectively. Use of "Lab-score" would have resulted in misdiagnosis of 7 (30%) infants with IBI. CONCLUSIONS: In well-appearing young infants with FWS the "Lab-score" seems a more useful tool for ruling in, rather than ruling out, SBI. Its accuracy for IBI prediction was unsatisfactory.