Diagnostic performance of smear microscopy and incremental yield of Xpert in detection of pulmonary tuberculosis in Rwanda

Abstract

BackgroundTuberculosis control program of Rwanda is currently phasing in light emitting diode-fluorescent microscopy (LED-FM) as an alternative to Ziehl-Neelsen (ZN) smear microscopy. This, alongside the newly introduced Xpert (Cepheid, Sunnyvale, CA, USA) is expected to improve diagnosis of tuberculosis and detection of rifampicin resistance in patients at health facilities. We assessed the accuracy of smear microscopy and the incremental sensitivity of Xpert at tuberculosis laboratories in Rwanda.MethodsThis was a cross-sectional study involving four laboratories performing ZN and four laboratories performing LED-FM microscopy. The laboratories include four intermediate (ILs) and four peripheral (PLs) laboratories. After smear microscopy, the left-over of samples, of a single early-morning sputum from 648 participants, were tested using Xpert and mycobacterial culture as a reference standard. Sensitivity of each test was compared and the incremental sensitivity of Xpert after a negative smear was assessed.ResultsA total of 96 presumptive pulmonary tuberculosis participants were culture positive for M. tuberculosis. The overall sensitivity in PL of ZN was 55.1 % (40.2–69.3 %), LED-FM was 37 % (19.4–57.6 %) and Xpert was 77.6 % (66.6–86.4 %) whereas in ILs the same value for ZN was 58.3 % (27.7–84.8 %), LED-FM was 62.5 % (24.5–91.5 %) and Xpert was 90 (68.3–98.8 %). The sensitivity for all tests was significantly higher among HIV-negative individuals (all test p <0.05). The overall incremental sensitivity of Xpert over smear microscopy was 32.3 %; p < 0.0001. The incremental sensitivity of Xpert was statistically significant for both smear methods at PL (32.9 %; p = 0.001) but not at the ILs (30 %; p = 0.125) for both smear methods.ConclusionsOur study findings of the early implementation of the LED-FM did not reveal significant increment in sensitivity compared to the method being phased out (ZN). This study showed a significant incremental sensitivity for Xpert from both smear methods at peripheral centers where majority of TB patients are diagnosed. Overall our findings support the recommendation for Xpert as an initial diagnostic test in adults and children presumed to have TB.

Diagnostic Accuracy of Xpert MTB Compared to Smear Microscopy in Pulmonary vs Extrapulmonary Tuberculosis

“…The sensitivity of Xpert MTB in our study is 39.8% higher than the smear microscopy while in a study carried by Anwar sheed khan et al has shown a sensitivity 40-50% higher than microscopy technique. 15 Our study depicts the same results regarding sensitivity and specificity.…”

United Kingdom–East and Southern Africa Partnership at the Forefront of Developing the First Ever Test that Measures Patient Tuberculosis Burden in Hours

“…Additionally, because of its low sensitivity, smear microscopy is often negative a few weeks into treatment when patients still have a significant mycobacterial load. 14…”

The analysis of evolution in eradicating mortalities caused by infectious diseases in East and Central African Countries coinciding with gross national income

“…On the same hand, the significance of the economic impact on the livestock production sector is currently distributing tuberculosis, whereas TB prevalence increased with increasing people size and with farms having poor management of income [15][16][17][18]. And then this factor lead to the number of new cases of TB in 2017 was significantly higher than in 2013-2016 in Uganda [19], in Rwanda [20], in Kenya [21,22], especially, most of them are classified in high global TB burden countries [23] and others countries [24]. These infectious diseases not only occurred in Sub-Sahara but general are global, for example in 2013, there were 1.3 million AIDS mortalities in the top 30 countries representing 87% of global AIDS mortalities [25].…”