Validation of a predictive model for identifying febrile young infants with altered urinalysis at low risk of invasive bacterial infection

Abstract

In 2015, a predictive model for invasive bacterial infection (IBI) in febrile young infants with altered urine dipstick was published. The aim of this study was to externally validate a previously published set of low risk criteria for invasive bacterial infection in febrile young infants with altered urine dipstick. Retrospective multicenter study including nine Spanish hospitals. Febrile infants ≤90 days old with altered urinalysis (presence of leukocyturia and/or nitrituria) were included. According to our predictive model, an infant is classified as low-risk for IBI when meeting all the following: appearing well at arrival to the emergency department, being >21 days old, having a procalcitonin value <0.5 ng/mL and a C-reactive protein value <20 mg/L. IBI was considered as secondary to urinary tract infection if the same pathogen was isolated in the urine culture and in the blood or cerebrospinal fluid culture. A total of 391 patients with altered urine dipstick were included. Thirty (7.7 %) of them developed an IBI, with 26 (86.7 %) of them secondary to UTI. Prevalence of IBI was 2/104 (1.9 %; CI 95% 0.5-6.7) among low-risk patients vs 28/287 (9.7 %; CI 95% 6.8-13.7) among high-risk patients (p < 0.05). Sensitivity of the model was 93.3 % (CI 95% 78.7-98.2) and negative predictive value was 98.1 % (93.3-99.4). Although our predictive model was shown to be less accurate in the validation cohort, it still showed a good discriminatory ability to detect IBI. Larger prospective external validation studies, taking into account fever duration as well as the role of ED observation, should be undertaken before its implementation into clinical practice.

Factors Associated with Adverse Outcomes among Febrile Young Infants with Invasive Bacterial Infections

“…Although a small number of studies have demonstrated worse outcomes for younger infants with IBI, most have focused solely on mortality, and age cutoffs defining younger infants differed. (28–32) Some studies on IBI in young infants have excluded premature infants altogether;(33, 34) and very few have reported outcomes data in relation to prematurity. (18) Age-stratified outcomes data for infants with IBI, particularly febrile infants, has been identified as a research priority.…”

A positive nitrite test was an independent risk factor for invasive bacterial infections in infants under 90 days of age with fever without source

“…3,6 However, when they evaluated the performance of the urine dipstick, these models did not assess the performance of leucocyte esterase and the nitrite test separately. The presence of a positive result for nitrite and leucocyte esterase on urinalysis has been proven to be an independent risk factor for bacteraemia in young febrile infants, [8][9][10] but little is known about the specific value of the nitrite test. One study showed that a model that included the urinary nitrite test may be useful for predicting bacteraemia among adult patients with pyelonephritis.…”

Desarrollo de un modelo predictivo de bajo riesgo de infección invasiva secundaria en lactantes febriles menores de 90 días de vida con una infección del tracto urinario

“…La ITU es la infección bacteriana potencialmente grave en lactantes febriles menores de 90 días de vida [126][127][128] . Además, el riesgo de infecciones bacterianas invasivas secundarias a ITU, especialmente la bacteriemia, es mayor en estos pacientes 22,169,172 . El patrón oro para el diagnóstico de ITU es el crecimiento de un germen patógeno aislado en un cultivo de orina 71 .…”

“…Hemos analizado una muestra grande, derivada de un estudio multicéntrico prospectivo desarrollado para elaborar un modelo predictivo de pacientes con sospecha de ITU y bajo riesgo de desarrollar una infección bacteriana invasiva (IBI) 172 . La muestra se dividió en 6 grupos, dependiendo de los resultados de la tira de orina (positivo o negativo) y del número de colonias aislado en el cultivo de orina.…”

“…Sin embargo, los presentes estudios son los primeros que exploran esta cuestión en un población de nuestro entorno, y con marcadores analíticos de uso común en la práctica clínica europea, como la procalcitonina y la proteína C reactiva, en lugar de otros habituales en Estados Unidos, como el contaje manual de cayados. Nuestro trabajo se diferencia del de Schnadower en que se centra en aquellos lactantes que tienen una sospecha de infección del tracto urinario, que es con lo que un médico se enfrenta en Urgencias, y por otro lado, no busca aquellos pacientes con bajo riesgo de complicaciones de la infección urinaria, sino que busca seleccionar pacientes con bajo riesgo de bacteriemia o meningitis 172 . Cuando un clínico evalúa un lactante febril en Urgencias, lo que trata fundamentalmente de determinar es si ese paciente puede tener una de estas dos infecciones, que pueden hacer peligrar la vida del paciente en cuestión de pocas horas.…”