Polymerase chain reaction in clinically suspected genitourinary tuberculosis: comparison with intravenous urography, bladder biopsy, and urine acid fast bacilli culture.

OBJECTIVES: To evaluate the role of urinary polymerase chain reaction (PCR) in the detection of Mycobacterium tuberculosis (MTb) in patients with a clinical suspicion of genitourinary tuberculosis (GUTB) and to compare its sensitivity with intravenous urography (IVU), bladder biopsy, and urine culture for acid fast bacilli (AFB).

METHODS: The study was carried out between September 1997 and December 1998 in 42 patients with a clinical suspicion of GUTB. Their clinical features, organ involvement, and investigation results were studied. The diagnostic yield of urinary PCR for MTb and its sensitivity in comparison with routine urine AFB culture, bladder biopsy, and IVU were assessed.

RESULTS: There were 25 male and 17 female patients, with a mean age of 31.04 years. Patients suspected of having GUTB most often presented with irritative voiding symptoms. Two patients had abnormal renal parameters. Of the 42 patients clinically suspected of having GUTB, radiologic abnormalities suggestive of GUTB were found in 37 (88.09%); MTb was isolated in the urine AFB culture in 13 (30.95%); bladder biopsy was positive in 11 (45.83%); and urinary PCR for MTb was positive in 34 cases (80.95%). Of 35 cases of proven GUTB, IVU was suggestive of the diagnosis in 32 (91.42%) and MTb was isolated in the urine AFB culture in 13 cases (37.14%). Bladder biopsy was positive in 11 (45. 83%) of 24 patients in whom biopsy was taken, and urinary PCR for MTb was positive in 33 (94.29%).

CONCLUSIONS: A high index of suspicion is necessary for a diagnosis of GUTB. In clinically suspected cases, IVU may be suggestive of GUTB, but it is not specific. In the present study, IVU was suggestive in 88.09% of patients. MTb was isolated in the urine AFB culture in only 37.14% of patients, and bladder biopsy was positive in 45.83%. Urinary PCR for MTb was the most sensitive indicator and was positive in 94.29% of patients. It is evident from this series that PCR provides a much faster diagnosis of urinary MTb. It is a rapid, sensitive, and specific diagnostic method and avoids a delay in starting treatment.