DISCUSSION
The current study was conducted for the evaluation and performance of diagnostic accuracy of GeneXpert MTB/RIF in detection of TB. The results of GeneXpert were also compared with other diagnostic methodologies including MGIT culture method and ZN staining method.
Out of the total 716 clinically TB suspects, 48.6% (N = 348) individuals were confirmed as positive for TB. The prevalence of TB positive individuals was higher in the middle age group individuals.
The characteristics of the clinically TB suspects between the TB positive and TB negative groups were similar except from smoking status. Smoking status in TB positive group individuals was significantly higher (27.3%) than TB negative group individuals (20.9%). Age and gender of the individuals between the groups did not differ significantly.
GeneXpert results were accurate and reliable with the sensitivity of 99.7% and specificity of 97.3%. The positive predictive value and negative predictive values were comparatively higher 97.1% and 99.7% respectively in GeneXpert result analysis. The chances of tested as being false positive and false negative were also as low as 2.7% and 0.3% respectively. The results of current study are in line with previous studies conducted for the performance of GeneXpert diagnostic method [9, 10].
Although the difference was not statistically significant, the disease was comparatively more prevalent in females than males. The reason for high prevalence in female gender might be inaccessibility to health care facilities. Women often face hindrances in gaining approach to diagnostic services, health examinations and in completing sufficient treatment. Furthermore, the burden of household assignments and childcare leave them with meager time to access health care and particularly tuberculosis care for themselves [15].
Smoking is an independent risk factor not only for active TB but also for latent TB cases. Smoking significantly increase the risk of acquiring and development of TB. According to study results, smoking status of individual was statistically significantly different between TB positive and TB negative groups. Higher rates were observed in TB positive individuals. We did not have information about passive smoking that could have explained the results further. Non-smoking individuals are easily exposed to passive smoking especially in the current study population as smoking indoor and in public places is not very rare event [16-18].
The strength of the present study is the large sample size and comparison with conventional TB diagnosis methodologies. Along with performance of GeneXpert techniques, we also performed comparative analysis between different available diagnostic techniques including ZN staining and MGIT culture. We also collected different socioeconomic parameters of study individuals that help in exploring the trends.
The limitations of our study included no information of human immunodeficiency viruses (HIV), hepatitis B virus (HBV) and hepatitis C virus (HCV). Although HIV is not very common in the study population but the prevalence of HBV and HCV is higher in the study population [18].