Efficacy of GeneXpert in Diagnosing Smear Negative Pulmonary Tuberculosis and Comparison to Culture

Objectives: Aim of present study is to observe the efficiency of GeneXpert MTB/RIF Assay in comparison to MTB culture on Lowenstein Jensen media in diagnosis of smear negative pulmonary tuberculosis cases.

Methods: This descriptive study was carried out in The University of Lahore in collaboration with King Edward Medical University/Mayo Hospital Lahore 11th September, 2020 to 10th April 2021. Smear negative for acid fast bacilli patients enrolled for anti TB treatment were the target population. After taking informed consent, patients were asked to submit first morning sputum sample for culture on Lowenstein Jensen Medium and GeneXpert.

Results: A total of 345 smear negative TB patients were diagnosed clinically and/or on the basis of radiological findings with mean age of 38.28±17.93,consisting of 47.5% male and 52.5% females recruited in this study. History of TB contact was present among 41.4% patients whereas history of smoking and diabetes remained to be 27.2% and 17.4% respectively. Culture showed significantly higher rate (35.1%) (p-value <0.05) of detection of MTB as compared to GeneXpert (21.5%). A sensitivity of 56.01% was calculated for GeneXpert whereas for culture on LJ medium it was 60.63%.

Conclusion: Sensitivity of GeneXpert MTB/RIF Assay is a bit low in diagnosing the SNPT patients as compared to the culture but still registers itself as a handsome tool in terms of promptness and definite detection of MTB complex. Further provision of rifampicin susceptibility is bonus in same time.