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



This 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.



A 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.



Our 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.
National Reference Laboratory Division, Rwanda Biomedical Centre, Kigali, Rwanda. cldsemuto@gmail.com.
Jean Claude Semuto
JC
Ngabonziza
Department of Medical Microbiology, Makerere University College of Health Sciences, School of Biomedical Sciences, Kampala, Uganda.|Department of Global Health and Amsterdam Institute of Global Health and Development, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands.
Willy
W
Ssengooba
Department of Medical Microbiology, School of Medicine, College of Health Sciences, University of Nairobi, Nairobi, Kenya.
Florence
F
Mutua
Mycobacteriology Unit, Institute of Tropical Medicine Prince Leopold, Antwerp, Belgium.
Gabriela
G
Torrea
Tuberculosis and other respiratory diseases Division, Rwanda Biomedical Centre, Kigali, Rwanda.
Augustin
A
Dushime
Tuberculosis and other respiratory diseases Division, Rwanda Biomedical Centre, Kigali, Rwanda.
Michel
M
Gasana
Pôle de microbiologie médicale, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium.
Emmanuel
E
Andre
Biomedical Laboratory Sciences Department, School of Allied Health Sciences, College of Medicine and Health Sciences, University of Rwanda, Kigali, Rwanda.
Schifra
S
Uwamungu
Management Sciences for Health, Pretoria, South Africa.
Alaine Umubyeyi
AU
Nyaruhirira
Department of Medical Microbiology, School of Medicine, College of Health Sciences, University of Nairobi, Nairobi, Kenya.
Dufton
D
Mwaengo
Clinical Biology Department, School of Medicine and Pharmacy, College of Medicine and Health Sciences, University of Rwanda, Butare, Rwanda.
Claude Mambo
CM
Muvunyi
D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D003955:Diagnostic Tests, Routine; D024881:Drug Resistance, Bacterial; D005260:Female; D006268:Health Facilities; D006801:Humans; D007753:Laboratories; D008297:Male; D008856:Microscopy, Fluorescence / Q000379:methods*; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000472:pathogenicity; D012293:Rifampin / Q000627:therapeutic use; D012432:Rwanda; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D055815:Young Adult
D012293:Rifampin
Incremental yield of Xpert; LED-FM versus ZN; Tuberculosis diagnosis in Rwanda; Tuberculosis microscopy in routine conditions