Objective: Nowadays, the use of flow-cytometry for the screening of urine samples is extended, but appropriate cut-off points for each population group are yet to be established. The objective of this study was to evaluate the Sysmex UF-1000i® cytometer as a screening method for detection of asymptomatic bacteriuria (AB) and Group B Streptococcus (GBS) in pregnant women.
Methods: Urine samples obtained during pregnancy between January-July 2019 were both processed with the Sysmex UF-1000i® and also cultured. Demographic data, flow-cytometry parameters and the result of the urine culture were collected. To assess the performance of the flow-cytometer for detection of AB and GBS, receiver operating characteristic (ROC) curves for the BACT/μL variable were applied.
Results: A total of 33,687 urine samples were received, among which 1,443 (4.3%) belonged to pregnant women. Urine culture was positive in 82 (5.7%) samples, 1,295 (89.7%) were negative and 66 (4.6%) were considered contaminated. GBS was isolated in 69 (4.8%) patients and 46 (66.7%) with a microbial count below 10E4 CFU/mL. For AB detection, the cut-off point of 550 BACT/μL yielded a sensitivity of 91.5%, a negative predictive value of 99.3% and could avoid culturing 74.1% of the samples. No cut-off value could be established for GBS detection.
Conclusions: Although the Sysmex UF-1000i® system is a valid screening method for the AB detection in pregnant population, it is not useful for the identification of GBS bacteriuria in our area. Therefore, the conventional urine culture is still required during pregnancy.
Objetivos: . Aunque se ha generalizado el uso de la citometría de flujo como método automatizado de cribado previo al urocultivo, los puntos de corte óptimos para cada grupo poblacional no están homogéneamente establecidos. El objetivo del presente estudio ha sido determinar el rendimiento del sistema Sysmex UF-1000i® en la detección de bacteriuria asintomática (BA) y la colonización por estreptococo grupo B (EGB) en la población gestante.
Material y m: étodos. Las orinas recibidas entre enero y julio de 2019 se analizaron mediante Sysmex UF-1000i® y paralelamente se cultivaron. Se recogieron variables demográficas, parámetros del citómetro y el resultado del urocultivo. El análisis del rendimiento del citómetro se realizó mediante curvas receiver operating characteristic (ROC) para la variable BACT/ µL respecto a la detección de BA y EGB.
Resultados: De 33.687 muestras de orina recibidas, 1.443 (4,3%) correspondían a embarazadas. El urocultivo fue positivo en 82 (5,7%) muestras, 1.295 (89,7%) negativas y 66 (4,6%) contaminadas. El EGB se identificó en 69 (4,8%) gestantes, siendo el recuento inferior a 104 UFC/mL en 46 (66,7%) casos. Utilizando el punto de corte de 550 BACT/μL (sensibilidad, 91,5%; valor predictivo negativo, 99,3%) en la detección de la BA se evitaría sembrar el 74,1% de las muestras. Sin embargo, no se pudo establecer ningún punto de corte para EGB.
Conclusiones: Aunque Sysmex UF-1000i® es una herramienta válida para el cribado de BA en la mujer embarazada en nuestro medio, no es útil para detectar EGB; por lo que continúa siendo necesario realizar el urocultivo convencional en este subgrupo poblacional.
Keywords: GBS; asymptomatic bacteriuria; flow cytometry; pregnancy.
©The Author 2020. Published by Sociedad Española de Quimioterapia. This article is distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)(https://creativecommons.org/licenses/by-nc/4.0/).