Diagnosis of Mycobacterium tuberculosis using GeneXpert MTB / RIF and TB-LAMP techniques from pulmonary and extra-pulmonary TB patients in Iraq

Abstract

Tuberculosis is considered one globally public health problem, particularly in unindustrialized countries. The disease has an increasing threat to public health, causing high morbidity and mortality rates. So, rapid diagnosis is critical to diminish the death and interfere with transmission. In this study, GeneXpert MTB/RIF and Loop-Mediated Isothermal Amplification (TB-LAMP) assays were utilized for the rapid molecular diagnosis of Mycobacterium tuberculosis bacteria and compared sensitivity and specificity of Mycobacterium tuberculosis bacteria; these tests with acid-fast bacilli staining in pulmonary and extra-pulmonary clinical specimens from Iraqi patients in Baghdad capital. 141 pulmonary and extra-pulmonary samples were collected and tested for tuberculosis detection. Acid-fast bacilli, TB-LAMP and GeneXpert MTB/RIF methods were used to diagnose tuberculosis. Of 141 tuberculosis specimens, 58 were acid-fast bacilli smear-positive, while 90 samples were positive for Mycobacterium tuberculosis by GeneXpert MTB/RIF assay and 78 by TB-LAMP assay. The results reported a high sensitivity rate of GeneXpert MTB/RIF assay compared to the TB-LAMP and bacilli staining method. The sensitivity of GeneXpert was 63.83%, specificity 50%; positive and negative predictive values were 58.36% to 68.96% and 42.73% to 57.27%, respectively. TB-LAMP sensitivity was 55.32%, specificity 50%; positive and negative predictive values were 49.61% to 60.89% and 43.70% to 56.30%, respectively, while the sensitivity of bacilli staining was 41.13%, specificity 50%; positive and negative predictive values were 35.26% to 47.27% and 44.88% to 55.12%, respectively, these values are dependent on disease prevalence. We concluded that the GeneXpert MTB/RIF test is more sensitive and specific than the TB-LAMP and both techniques are more sensitive and specific than the conventional acid-fast staining method for both pulmonary and extra-pulmonary specimens. Despite culture remaining the gold standard for laboratory confirmation of TB, GeneXpert MTB/RIF and TB-LAMP should become standard practice for patients with suspected TB, and all clinicians and public health programs for TB control should have access to molecular testing for TB to shorten diagnosis time. Keywords. Mycobacterium tuberculosis; Pulmonary TB; Extrapulmonary TB; GeneXpert MTB/RIF; TB-LAMP; A.F.B