Application of Home Validated Panel Dna Materials for Proficiency Testing of Who Endorsed Molecular Assays: Mtbdrplus and Xpert Mtb/Rif Assay
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Date
2016-06
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Addis Ababa University
Abstract
Background: Tuberculosis (TB) is a major public health problem in Ethiopia. Laboratory plays an important role in
the diagnosis of TB and its treatment monitoring. Quality assured molecular drug susceptibility assay is an essential
for rapid detection of MDR-TB cases and early treatment initiation Proficiency testing is one of the EQA methods in
evaluating the quality service delivery however, it was not widely applied for molecular assays in Ethiopia mainly
due to the inadequate capacity of preparing PT DNA panels’ in-country.
Objective: The aim of this study was to assess Application of Homemade and validated panel DNA Materials for
Proficiency Testing of the WHO endorsed Molecular Assays (GenoType® MTBDRplus and Xpert MTB/RIF
assays) in TB Culture and DST laboratories, and in selected GeneXpert sites of Ethiopia.
Methods: A cross sectional study was conducted in five regional reference laboratories and two specialized hospital
TB culture and DST laboratories which have molecular GenoType® MTBDRplus assay of Ethiopia, and in eight
selected health facilities with Xpert MTB/RIF testing sites in Addis Ababa during the period between July 2015 and
January 2016. PT DNA materials were validated at EPHI, NTRL and distributed to MTBDRplus and Xpert MTB/RIF
testing facilities. All data from participating laboratories were captured and analyzed using SPSS version 20. A total
of 194 (130 for MTBDRplus and 64 Xpert MTB/RIF) DNA panels were distributed to regional reference and hospital
TB laboratories. Test results agreement between the participant laboratories and reference were estimated using
Kappa statistics. The sensitivity, specificity, predictive value susceptible, predictive value resistance, accuracy and
reproducibility of participant laboratories were calculated against the reference lab.
Results: 130 panel samples with a combination of 65 (50%) spiked sputum and 65 (50%) extracted DNA were tested
in seven Regional Reference Laboratories which have MTBDRplus assay. Almost all, 129 (99.2 %) were correctly
reported to the Isoniazid and Rifampicin susceptibility. Sixty nine (53.1%) reported isolates were resistance to both
INH and RIF (MDR), 41 (31.5%) susceptible to both INH and RIF, and 19 (14.6%) INH susceptible but RIF
resistance strains correctly reported with respect to the reference result. There was 100% agreement in detecting
MDR and resistance to any of the two drugs (INH and RIF) (kappa = 1) but the agreement was 97.8% for the
detection of susceptible strains (Kappa = 0.9). Among 64 spiked sputum strains (32 M. tuberculosis DNA with no
RIF resistance and 32 M. tuberculosis DNA with RIF resistance (probe E Mutant detected ) distributed to GeneXpert
sites, all of them were correctly reported. Overall agreement on detection of M. tuberculosis and RIF susceptibility
was 100 % (Kappa =1.0).
Conclusion: There was an excellent agreement between the participant laboratories and the reference laboratory for
the detection M. tuberculosis and drug susceptibility using MTBDRplus and Xpert MTB/RIF assays. Therefore, we
can apply home validated PT DNA panels as one of the EQA methods for WHO endorsed molecular assays
MTBDRplus, whereas in the Xpert MTB/RIF assay a large scale validation is important to use as Panel test since,
the sites we used for this study in Addis Ababa, are small compared to the general population in Ethiopian context.
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Keywords
Molecular Assays, Validated Panel