Urine-Based Nested PCR for the Diagnosis of Mycobacterium tuberculosis: A Comparative Study Between HIV-Positive and HIV-Negative Patients

While tuberculosis (TB) can be diagnosed by microscopy and culture, the sensitivity of Ziehl-Neelsen staining is variable and culture results require 4 - 8 weeks to be determined. Polymerase chain reaction (PCR) and its modifications, including nested PCR, might be promising methods for the rapid diagnosis of TB.
This study aimed to evaluate the performance of nested PCR on urine samples of human immunodeficiency virus (HIV)-positive and -negative patients with different manifestations of clinical TB.
In a prospective study, three early-morning urine samples from 100 patients with pulmonary TB (PTB) or extrapulmonary TB (EPTB) were evaluated using a molecular target with insertion element IS6110, specific to the Mycobacterium tuberculosis genome, and nested PCR was performed. The results were analyzed with SPSS version 22.
A total of 100 patients, including 74 (74%) with PTB and 26 (26%) with EPTB, were enrolled. Positive smears were seen in 38 patients (38%). Lymph nodes were the most commonly involved organ in 14 of the 26 (53.8%) EPTB patients (13.5%). Seven (23.1%) of the EPTB patients were HIV-positive. Urine PCR was positive in only 28 patients (28%). Seven HIV-positive patients with PTB showed positive urine PCR results. Moreover, PCR results were positive in only one of the seven HIV-positive subjects with EPTB. Positive PCR results were found in 20 of the 73 HIV-negative patients (27.4%) and in 8 of the 27 HIV-positive patients (29.6%). Therefore, there was no significant difference between the HIV-negative and HIV-positive patients for urine PCR (sensitivity 29.6%, specificity 72.6%; positive and negative predictive values 28% and 72%, respectively; P = 0.138).
Nested PCR showed the same sensitivity in HIV-positive and HIV-negative patients. It can be applied as a rapid technique for the diagnosis of TB.