Microscopic estimation of bacteria and cells in urine

Abstract

An improved technique for diagnosing acute urinary tract infections (UTI) by means of microscopic estimation of bacteria, leucocytes, erythrocytes and epithelial cells in urine was tested clinically in a total of 1,807 samples obtained from hospital departments. Marked bacteriuria (≧10⁵ bacteria per ml of urine) was found microscopically in 13.1% of the urines. Of these 1.9% were falsely positive. Altogether 3.5% of the samples were falsely negative. When the sample collection was controlled carefully and detailed information on possible collection errors was given regularly, sensitivity and specificity indices of the microscopic technique were 85.3 and 98.1, respectively. Microscopic finding of cocci, e.g. Enterococci andStr. agalactiae, was more difficult than that of rods. Alongside bacteriuria, finding of leucocytes (>5 leucocytes per microscopic field) was of great importance for UTI diagnostics, and it strengthened further the microscopic diagnosis, while erythrocytes and epithelial cells were of very poor significance for UTI diagnosis. The results show that the microscopic technique described here is a reliable and suitable method for UTI diagnostics in routine clinical laboratories which examine daily large numbers of samples, most of them negative.