OBJECTIVETo establish a laboratory method for detection of Mycobacterium tuberculosis in sputum based on variable number tandem repeat (VNTR).

METHODSMycobacterium tuberculosis was tested by VNTR and fluorescent quantitative reverse transcription polymerase chain reaction (FQ-PCR) in 130 sputum samples from patients with pulmonary tuberculosis and 200 specimens from patients with other lung diseases. According to the amplification conditions and clinical detection needs, MTUB21, MUTB04, QUB18, QUB26, QUB11b, MIRU31, MIRU10 and MIRU26 were selected as test targets. The results of VNTR and FQ-PCR were compared with Lowenstein-Jensen culture and clinical diagnosis, and analyzed by chi-square test.

RESULTSWith the results of L-J culture as the standard, the sensitivity and specificity of VNTR were 93.1% (108/116) and 97.7% (209/214), and those of FQ-PCR were 94.0% (109/116) and 96.7% (207/214), respectively; no significant difference was observed between two groups (χ2=0.352, P=0.569). Using the clinical diagnosis as the standard, the sensitivity and specificity of VNTR were 86.9% (113/130) and 100% (200/200), and those of FQ-PCR were 87.7% (114/130) and 99.0% (198/200), respectively; the difference was not statistically significant (χ2=0.030, P=0.862). In 113 VNTR positive samples, the molecular codes differed from each other in 98.2% samples (111/113); only 2 samples had identical code (5-4-6-8-5-5-3-8).

CONCLUSIONThe study suggests that VNTR provides a promising method for diagnosis of clinical tuberculosis.