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. 2019 Dec 30;19(1):1090.
doi: 10.1186/s12879-019-4728-2.

Diagnosis of tuberculosis from smear-negative presumptive TB cases using Xpert MTB/Rif assay: a cross-sectional study from Nepal

Priyatam Khadka  1   2 , Januka Thapaliya  3 , Ramesh Bahadur Basnet  4 , Gokarna Raj Ghimire  5 , Jyoti Amatya  3 , Basista Parsad Rijal  4
Affiliations

Diagnosis of tuberculosis from smear-negative presumptive TB cases using Xpert MTB/Rif assay: a cross-sectional study from Nepal

Priyatam Khadka et al. BMC Infect Dis. .

Abstract

Background: In most developing countries, smear-negative pulmonary TB (SNPT) often gets missed from the diagnosis of consideration, though it accounts 30-65% of total PTB cases, due to deficient or inaccessible molecular diagnostic modalities.

Methods: The cross-sectional study enrolled 360 patients with clinical-radiological suspicion of SNPT in Tribhuvan University Teaching Hospital (TUTH). The patient selection was done as per the algorithm of Nepal's National Tuberculosis Program (NTP) for Xpert MTB/RIF testing. Participants' demographic and clinical information were collected using a pre-tested questionnaire. The specimens were collected, processed directly for Xpert MTB/RIF test according to the manufacturer's protocol. The same samples were stained using the Ziehl-Neelsen technique then observed microscopically. Both findings were interpreted; rifampicin-resistant, if obtained, on Xpert testing was confirmed with a Line Probe Assay.

Result: Of 360 smear-negative sputum samples analyzed, 85(23.61%) found positive while 3(0.8%) of them were rifampicin resistance. The infection was higher in males, i.e. 60(25.3%) compared to female 25(20.3%). The age group, > 45(nearly 33%) with median age 42 ± 21.5, were prone to the infection. During the study period, 4.6% (515/11048) sputum samples were reported as smear-positive in TUTH. Consequently, with Xpert MTB/RIF assay, the additional case 16.5% (n = 85/515) from smear-negative presumptive TB cases were detected. Among the most occurring clinical presentations, cough and chest pain were positively associated with SNPT. While upper lobe infiltrates (36.4%) and pleural effusion (40.4%) were the most peculiar radiological impression noted in PTB patient. 94 multi-drug resistant(MDR) suspected cases were enrolled; of total suspects, 29(30.8%) samples were rifampicin sensitive, 1(1.06%) indeterminate, 3(3.19%) rifampicin-resistant while remaining of them were negative. 2(2.2%) MDR cases were recovered from the patient with a previous history of ATT, of total 89 previously treated cases enrolled However, a single rifampicin-resistant from the new suspects.

Conclusion: With an application of the assay, the additional cases, missed with smear microscopy, could be sought and exact incidence of the diseases could be revealed.

Keywords: Line probe assay; MDR-TB; Mycobacterium tuberculosis; Smear-negative; Xpert MTB/Rif assay.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
The total case detection of SNPT with Xpert MTB/RIF Assay is shown in the pie chart. Each portion of pie chart indicates the number/percentage of enrolled cases and their result
Fig. 2
Fig. 2
Line probe assay showing mutated genomic sequences
See this image and copyright information in PMC

References

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