Comparison of a DNA based PCR method with conventional methods for the detection of M. tuberculosis in Jos, Nigeria

To achieve early diagnosis and effective treatment of pulmonary tuberculosis, simple and sensitive methods that enhance the detection of Mycobacterium tuberculosis (M. tuberculosis) from clinical specimens are needed. This study compared the effectiveness and suitability of an insertion sequence (IS 6110) based polymerase chain reaction (PCR) assay with conventional methods for the detection of M. tuberculosis from clinical specimens in a resource-limited setting.

Sputa from 101 HIV-positive patients and 40 clinical specimens (sputa, gastic wash out, ascitic fluid, pleural fluid and cerebrospinal fluid) collected from children (HIV status unknown), all suspected for pulmonary tuberculosis at the Jos University Teaching Hospital, Jos, (JUTH) Nigeria, were examined by Ziehl Neelsen (ZN) smear microscopy, Lowenstein Jensen's (LJ) egg-based culture, and PCR methods for the detection of M. tuberculosis.

Mycobacteria was detected in 45/101 (44.6%) of the specimens from the HIV-positive patients and comprised of 6% ZN(+)culture(+)PCR(+), 4% ZN(-)culture(+)PCR(-), 16% ZN(-)culture(+)PCR(+) and 19% ZN(-)culture(-)PCR(+). Twenty-two of forty (55%) children were positive with 0% smear microscopy; 4/40 (10%) culture(+)PCR(+); and 18/40 (45%) culture(-)PCR(+). The sensitivity and specificity of the PCR for the HIV-positive patients were 85% and 74% respectively against 23% and 100% for ZN smear microscopy.

The IS6110 PCR is a rapid and sensitive method that is specific for the M. tuberculosis complex group. It is simple in our experience and increased the detection of M. tuberculosis from the specimens examined. We suggest its use for the detection of M. tuberculosis in high TB and HIV burden areas.