Reddy S, Ntoyanto S, Sakadavan Y, Reddy T, Mahomed S, Dlamini M, Spooner B, Ramjee G, Coutsoudis A, Ngomane N, Naidoo K, Mlisana K, Kiepiela P. Detecting
Mycobacterium tuberculosis using the loop-mediated isothermal amplification test in South Africa.
Int J Tuberc Lung Dis 2018;
21:1154-1160. [PMID:
28911361 DOI:
10.5588/ijtld.16.0863]
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Abstract
SETTING
In South Africa, KwaZulu-Natal is the epicentre of the human immunodeficiency virus (HIV) epidemic, where approximately 70% of people with tuberculosis (TB) are co-infected with HIV. Undiagnosed TB contributes to high mortality in HIV-infected patients. Delays in diagnosing TB and treatment initiation result in prolonged transmission and increased infectiousness.
OBJECTIVE
To evaluate the LoopampTM MTBC Detection kit (TB-LAMP; based on the loop-mediated isothermal amplification assay), smear microscopy and Xpert test with the gold standard of mycobacterial culture.
METHODS
Sputum samples were collected from 705 patients with symptoms of pulmonary TB attending a primary health care clinic.
RESULTS
The TB-LAMP assay had significantly higher sensitivity than smear microscopy (72.6% vs. 45.4%, P < 0.001), whereas specificity was slightly lower (99% vs. 96.8%, P = 0.05), but significantly higher than Xpert (92.9%, P = 0.004). There was no significant difference in sensitivity of smear-positive, culture-positive and smear-negative, culture-positive sputum samples using TB-LAMP vs. Xpert (respectively 95.9%/55.9% vs. 97.6%/66.1%; P =0.65, P = 0.27). The positive predictive value of TB-LAMP was significantly higher than that of Xpert (87.5% vs. 77.0%; P = 0.02), but similar to that of smear microscopy (94.2%; P = 0.18). The negative predictive value was respectively 91.9%, 92.5% (P = 0.73) and 83.1% (P = 0.0001).
CONCLUSION
Given its ease of operability, the TB-LAMP assay could be implemented as a point-of-care test in primary health care settings, and contribute to reducing treatment waiting times and TB prevalence.
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