Study On Molecular Biology Diagnostic New Method Application In The Diagnosis Of Tuberculous Lymphadenitis

Objectives: Superficial tuberculous lymphadenitis is diagnosed by imaging,bacteriology, pathology, but these diagnostic means are not ideal ones for sensitivity and specificity. In recent years, the detection method of the specific gene of Mycobacterium tuberculosis has developed rapidly, which has the advantages of rapid and accurate detection. So, the prospective study, evaluates the application of the Xpert MTB / RIF, fluorescence quantitative polymerase chain reaction(PCR) and high resolution melting curve method in diagnosis of superficial tuberculous lymphadenitis, and compares them with the common methods to diagnosis.Methods: Between March 2015 and Jan 2016, 86 consecutive cases of suspected TB lymph node specimens and 13 cases of non-tuberculous lymph node samples were collected and divided into two groups using needle aspiration and biopsy methods. One group was used for Xpert MTB/RIF, BACTEC MGIT960 culture, and L-J culture diagnosis. The other group was used for pathologic diagnosis, Mycobacterium tuberculosis Isoniazid and Rifampicin Resistance mutation Test, and PCR diagnosis of tissue specimens.Results: There were 81 patients clinically suspected to have tuberculous lymphadenitis. 74 of whom were MTBC(Mycobacterium Tuberculosis Complex)positive based on Xpert MTB/RIF(91.4%), 60 of whom were FFPE-PCR positive,Twenty-four(29.6%) and thirteen(16%) patients were BACTEC MGIT960 and L-J culture-positive, respectively thirty-eight patients were pathologically-diagnosed with tuberculous lymphadenitis(46.9%).The specificity of all of these methods was100%.The sensitivity of molecular biology detection technology is significantly higher than that of traditional diagnostic methods, Xper MTB/RIF is the most sensitive diagnostic method. In rifampicin resistance detection, MTB/RIF Xpert detected 3 cases of rpoB gene mutations(3.7%), the drug susceptibility test(DST)of Mycobacterium tuberculosis was detected in 2 cases(2.4%).These two cases were in accordance with the Xpert test results. Isoniazid resistance, melting curve detection of isoniazid resistant mutant in 7 cases(8.1%), 1 case with drug sensitivity results support. Molecular biology technology showed a higher sensitivity in drug resistance testing, and the coincidence rate was better. Xpert MTB/RIF in the detection of rifampin resistance is most sensitive, but cannot be used for drug resistance detection of isoniazid. The positive rate of melting curve method is low, but it can diagnose drug resistance to rifampin and isoniazid two first-line anti TB drugs.Conclusions: Molecular detection is helpful to improve the sensitivity of diagnosis of tuberculous lymphadenitis. Molecular detection in the diagnosis of drug-resistant tuberculosis of lymph nodes plays an important role, which improves the sensitivity to rifampicin and isoniazid resistance test. The new combined diagnosis model consisting of molecular biology, pathology and bacteriology can improve the sensitivity of the diagnosis of tuberculous lymphadenitis. The prevalence of drug resistance in patients with tuberculous lymphadenitis is lower than that of the pulmonary tuberculosis. Rifampicin and isoniazid resistance does not occur at the same time, the number of patients with isoniazid resistance is more than the number of patients with rifampin resistance.