Eficacia de dos métodos semiautomáticos para la exclusión de bacteriuria

Abstract

A quick and reliable method for detecting bacteriuria would allow to exclude the presence of microorganisms in the urine on the same day the sample is obtained.Objectives. Two semiautomatic methods have been evaluated for bacteriuria screening, taking the semiquantitative culture as reference method. A prospective study of urine samples from patients suspected of having a urinary infection was designed. One method is based on bioluminescence that detects the presence of ATP liberated by the bacterial cell (Utiscreen-Coral Biomedical). The other semiautomatic method uses a nephelometry technique (Uro-quick). The results of each semiautomatic method were compared with the semiquantitative culture. Samples presenting counts > 104 UFC/ml of one or two microorganisms were considered as having urinary-tract infection (equivalent to significative bacteriuria). Cultures with counts < 5,000 UFC/ml or containing three or more microorganisms were classified as non-representative of significant bacteriuria. The nephelometric system allows to obtain results at two different times. Samples were divided into two groups to compare both situations. 1,090 urine samples, received consecutively, were considered. In the case of the bioluminescence system, the study was prolonged to 1,565 samples. The values obtained were: a) bioluminescence: general data, sensibilitiy (S) 5 94.4%; especificity (E) 5 72.8%; positive predictive value (PPV) 5 46.2% and negative predictive value (NPV) 5 98.2%; hospitalized patients only, S 5 97.5%; E 5 77.3%; PPV 5 61.2% and NPV 5 98.8%; and b) nephelometry: 195 min, S 5 96.7%; E 5 88.8%; PPV 5 67.9% and NPV 5 99.1%; 235 min, S 5 95.5%; E 5 81.0%; PPV 5 58.7% and NPV 5 98.4%. A negative predictive value from both methods under these conditions would allow them to be used in medical centers for the exclusion of bacteriuria.