Accuracy of a sequential approach to identify young febrile infants at low risk for invasive bacterial infection.

INTRODUCTION: Much effort has been put in the past years to create and assess accurate tools for the management of febrile infants. However, no optimal strategy has been so far identified. A sequential approach evaluating, first, the appearance of the infant, second, the age and result of the urinanalysis and, finally, the results of the blood biomarkers, including procalcitonin, may better identify low risk febrile infants suitable for outpatient management. OBJECTIVE: To assess the value of a sequential approach ('step by step') to febrile young infants in order to identify patients at a low risk for invasive bacterial infections (IBI) who are suitable for outpatient management and compare it with other previously described strategies such as the Rochester criteria and the Lab-score. METHODS: A retrospective comparison of three different approaches (step by step, Lab-score and Rochester criteria) was carried out in 1123 febrile infants less than 3 months of age attended in seven European paediatric emergency departments. IBI was defined as isolation of a bacterial pathogen from the blood or cerebrospinal fluid. RESULTS: Of the 1123 infants (IBI 48; 4.2%), 488 (43.4%) were classified as low-risk criteria according to the step by step approach (vs 693 (61.7%) with the Lab-score and 458 (40.7%) with the Rochester criteria). The prevalence of IBI in the low-risk criteria patients was 0.2% (95% CI 0% to 0.6%) using the step by step approach; 0.7% (95% CI 0.1% to 1.3%) using the Lab-score; and 1.1% (95% CI 0.1% to 2%) using the Rochester criteria. Using the step by step approach, one patient with IBI was not correctly classified (2.0%, 95% CI 0% to 6.12%) versus five using the Lab-score or Rochester criteria (10.4%, 95% CI 1.76% to 19.04%). CONCLUSIONS: A sequential approach to young febrile infants based on clinical and laboratory parameters, including procalcitonin, identifies better patients more suitable for outpatient management.

Diagnostic value of procalcitonin in well-appearing young febrile infants.

BACKGROUND AND OBJECTIVE: Procalcitonin (PCT) has been introduced in many European protocols for the management of febrile children. Its value among young, well-appearing infants, however, is not completely defined. Our objective was to assess its performance in diagnosing serious bacterial infections and specifically invasive bacterial infections (IBIs) in well-appearing infants aged <3 months with fever without source (FWS). METHODS: Well-appearing infants aged <3 months with FWS admitted to 7 European pediatric emergency departments were retrospectively included. IBI was defined as the isolation of a bacterial pathogen in blood or cerebrospinal fluid culture. RESULTS: We included 1112 infants who had PCT measured and a blood culture performed. IBI was diagnosed in 23 cases (2.1%). In the multivariate analysis including clinical and laboratory data, PCT was the only independent risk factor for IBI (odds ratio 21.69; 95% confidence interval [CI] 7.93-59.28 for PCT ≥ 0.5 ng/mL). Positive likelihood ratios for PCT ≥ 2 ng/mL and C-reactive protein (CRP) >40 mg/L were 11.14 (95% CI 7.81-15.89) and 3.45 (95% CI 2.20-5.42), respectively. Negative likelihood ratios for PCT <0.5 ng/mL and CRP <20 mg/L were 0.25 (95% CI 0.12-0.55) and 0.41 (95% CI 0.22-0.76). Among patients with normal urine dipstick results and fever of recent onset, areas under the receiver operator characteristic curve for PCT and CRP were 0.819 and 0.563, respectively. CONCLUSIONS: Among well-appearing young infants with FWS, PCT performs better than CRP in identifying patients with IBIs and seems to be the best marker for ruling out IBIs. Among patients with normal urine dipstick results and fever of recent onset, PCT remains the most accurate blood test.

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 (SBIs) in children with fever without source. We aimed to assess the Lab-score usefulness in predicting SBI, especially invasive bacterial infections (IBIs), in well-appearing infants <3 months with fever without source. METHODS: A multicenter retrospective study was conducted 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 (2.1%) of 1098. The positive and negative likelihood ratios of a score ≥3 for SBI prediction were 10.2 (95% confidence interval [CI]: 9.5-10.9) and 0.5 (95% CI: 0.5-0.5), respectively. The area under the receiver operating characteristic curve 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 infants with fever without source, the Lab-score seems a more useful tool for ruling in, rather than ruling out, SBI. Its accuracy for IBI prediction was unsatisfactory.