Evaluation of Diagnostic Performance of Line Probe Assay on Smear-Negative Samples of Pulmonary Tuberculosis

Sumi Nandwani; Sanjay Singhal; Dipti Gothi; Ritu Singhal; Naz Perween; Kavita Gupta; Raunak Bir; Jayanthi Gunasekaran; Anushka Soni; Urmila Chaudhary

doi:10.7759/cureus.58298

Evaluation of Diagnostic Performance of Line Probe Assay on Smear-Negative Samples of Pulmonary Tuberculosis

Cureus. 2024 Apr 15;16(4):e58298. doi: 10.7759/cureus.58298. eCollection 2024 Apr.

Authors

Affiliations

¹ Microbiology, Post Graduate Institute of Child Health, Noida, IND.
² Microbiology, Employee's State Insurance Corporation (ESIC) Hospital, Postgraduate Institute of Medical Sciences and Research (PGIMSR), New Delhi, IND.
³ Pulmonary and Critical Care Medicine, Employee's State Insurance Corporation (ESIC) Hospital, Postgraduate Institute of Medical Sciences and Research (PGIMSR), New Delhi, IND.
⁴ Microbiology, WHO National Reference Laboratory and Center of Excellence (TB) and National Institute of Tuberculosis and Respiratory Diseases, New Delhi, IND.

Abstract

Background: This study aims to compare the performance of line probe assay (LPA) on smear-negative samples with that of smear-positive samples for diagnosing pulmonary tuberculosis (PTB) and first-line drug sensitivity testing (FL DST).

Methods: A total of 196 sputum samples including both smear-positive (112) and negative (84) samples of patients suspected of PTB were subjected to LPA for TB detection and FL DST. TB culture followed by MPT 64 Ag was done and conventional FL DST was performed on all culture-positive isolates. Results of LPA on smear-negative were compared with smear-positive samples.

Results: The LPA confirmed the diagnosis of PTB in 104/112 smear-positive cases but in only 36/84 smear-negative cases. The assay had 47.36%, 72.72%, and 88.88% sensitivity and 86.96%, 95.23%, and 95.65% specificity in smear-negative cases compared to 89.09%, 95.83%, and 98.07% sensitivity and 100%, 98.36%, and 98.24% specificity in smear-positive cases for detecting Mycobacterium tuberculosis (MTB), rifampicin (RMP) resistance, and isoniazid (INH) resistance, respectively.

Conclusion: LPA performance was better on smear-positive than smear-negative sputum samples. Further larger studies are needed to justify the use of LPA on smear-negative pulmonary samples for diagnosis.

Keywords: acid-fast bacilli; diagnostic utility of lpa; first-line drug sensitivity testing; isoniazid resistance; line probe assay; mycobacterium tuberculosis complex detection; pulmonary tuberculosis; rifampicin resistance; smear-negative samples; ziehl-neelsen stain.