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Year : 2020  |  Volume : 12  |  Issue : 4  |  Page : 235-236
Comparison of conventional versus molecular semi-quantitative assay in presumptive pulmonary tuberculosis cases: A study from eastern India


1 Department of Microbiology, All India Institute of Medical Sciences, Bhubaneswar, Odisha, India
2 Department of Pulmonary Medicine and Critical Care, All India Institute of Medical Sciences, Bhubaneswar, Odisha, India

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Date of Submission13-Jun-2020
Date of Acceptance21-Jun-2020
Date of Web Publication30-Nov-2020
 

How to cite this article:
Purohit G, Mishra B, Mohapatra PR. Comparison of conventional versus molecular semi-quantitative assay in presumptive pulmonary tuberculosis cases: A study from eastern India. J Global Infect Dis 2020;12:235-6

How to cite this URL:
Purohit G, Mishra B, Mohapatra PR. Comparison of conventional versus molecular semi-quantitative assay in presumptive pulmonary tuberculosis cases: A study from eastern India. J Global Infect Dis [serial online] 2020 [cited 2021 Jan 26];12:235-6. Available from: https://www.jgid.org/text.asp?2020/12/4/235/302009


Sir,

India is one of the high tuberculosis (TB) burden countries. According to WHO global TB report 2018, India accounts for one-fourth of the global TB burden with an estimated 2.79 million incident cases.[1] Measurements of bacillary load have an important role in TB diagnostics. Semi-quantitative or quantitative measures of Mycobacterium tuberculosis bacilli present in pulmonary samples have been useful for determining severity of the disease, assessing risk of transmission or monitoring treatment response.[2],[3]

The present study aimed at comparative analysis of two assays used for semi-quantitation of bacillary load in presumptive pulmonary TB cases: Conventional (smear microscopy i.e., Ziehl Neelsen staining) and molecular (Xpert MTB/RIF assay). From February to July 2018, a total of 288 sputum samples were processed for both the assays. The Xpert MTB/RIF grading of very low (28 < Ct< 38), low (22 < Ct<28), medium (16 < Ct≤ 22) and high (Ct≤ 16) were compared with acid-fast bacilli (AFB) smear grading of negative and scanty, ≤1+, ≥1 + and ≥ 2+ respectively.[4] Spearman correlation test was used to calculate correlation between the two grading methods. P < 0.05 was considered significant.

Out of 288 sputum samples, four (1.4%) found to be Nontuberculous Mycobacteria by culture and MPT64 antigen detection method were excluded from the analysis. Out of 284 samples, M. tuberculosis was detected in 72 (25.3%) by the Xpert MTB/RIF assay, of which 47 (65.3%) could be detected by AFB smear microscopy.

The result for comparison of the Xpert MTB/RIF grading and AFB smear grading is described in [Table 1].
Table 1: Comparison of the Xpert MTB/RIF grading with acid-fast bacilli smear grading

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The Xpert MTB/RIF grading was found to have strong correlation with AFB smear grading (correlation coefficient 0.73, P < 0.001).

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

1.
World Health Organization. Global Tuberculosis Report. Geneva, Switzerland: World Health Organization; 2018.  Back to cited text no. 1
    
2.
Palaci M, Dietze R, Hadad DJ, Ribeiro FK, Peres RL, Vinhas SA, et al. Cavitary disease and quantitative sputum bacillary load in cases of pulmonary tuberculosis. J Clin Microbiol 2007;45:4064-6.  Back to cited text no. 2
    
3.
Perrin FM, Woodward N, Phillips PP, McHugh TD, Nunn AJ, Lipman MC, et al. Radiological cavitation, sputum mycobacterial load and treatment response in pulmonary tuberculosis. Int J Tuberc Lung Dis 2010;14:1596-602.  Back to cited text no. 3
    
4.
Blakemore R, Nabeta P, Davidow AL, Vadwai V, Tahirli R, Munsamy V, et al. A multisite assessment of the quantitative capabilities of the Xpert MTB/RIF assay. Am J Respir Crit Care Med 2011;184:1076-84.  Back to cited text no. 4
    

Top
Correspondence Address:
Dr. Baijayantimala Mishra
Department of Microbiology, All India Institute of Medical Sciences, Bhubaneswar - 751 019, Odisha
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jgid.jgid_179_20

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