Diagnostic relevance of the detection of Legionella DNA in urine samples by the polymerase chain reaction

Urine samples from 317 patients with pneumonia and from 242 patients withou t pneumonia were tested using a polymerase chain reaction (PCR) system for detection of the Legionella 58 rRNA gene. The results were compared with fi ndings obtained using the established methods for diagnosis of legionellosi s. Of the 317 patients with pneumonia, 58 had confirmed legionellosis, 35 h ad a presumptive Legionella infection, and 224 had no evidence of Legionell a infection as determined by conventional methods using published criteria. The PCR was positive for 42 patients with confirmed infections, yielding a sensitivity of 72.4%, Furthermore, 16 (47%) patients with presumptive legi onellosis and five (2.2%) patients without other evidence of Legionella inf ection had positive results. All samples from 242 patients without pneumoni a were PCR-negative. When the results for all patients were considered, the specificity of the assay was greater than or equal to 98.9%. The results d emonstrate that the sensitivity and specificity values of urinary PCR are i n the same range as those of established methods. The use of PCR in urine c omplements the repertoire of rapid diagnostic methods, especially for infec tions caused by legionellae not belonging to Legionella pneumophila serogro up 1, in which tests for detection of urinary antigen often fail.