There was no increase in MDR-TB prevalence in Zambia from 2001 to 2008; results from the two methods were similar. Molecular methods were quicker and simpler to use.

bThe performance of the Capilia TB-Neo assay, a new-generation assay, was assessed by determining its sensitivity, specificity, reproducibility, and cross-reaction with contaminating organisms. The sensitivity and specificity were 99.2 and 96.4% and 89.3 and 100% in pure and mixed-culture isolates, respectively. The kappa statistic was 95.0 and 77.9% in pure and mixed culture isolates, respectively. There was no cross-reaction with contaminating organisms. The Capilia TB assay is a rapid, simple, and inexpensive identification test for identification of mycobacterial culture isolates that has been evaluated extensively (1-7). A new generation of this assay, the Capilia TB-Neo assay (Capilia), has been developed, replacing the original assay (Y. Namba, 8 September 2010, European patent application EP 2226635 A1). The original assay has been shown to have sensitivity and specificity ranging from 92% to 100% (1, 2, 6). Cross-reaction with other mycobacteria and other bacteria has been demonstrated with the original assay (1, 7; Y. Namba, 8 September 2010, European patent application EP 2226635 A1). As a result, a new assay was developed to replace the original assay to take care of the cross-reaction and to improve the specificity (Y. Namba, 8 September 2010, European patent application EP 2226635 A1). So far, there are only two published studies that have evaluated this next-generation assay, and the studies show conflicting results. An overall reduction in sensitivity and specificity was observed by Gomathi et al. (8)-76% and 86%, respectively. However, Pokam et al. reported a sensitivity and specificity approaching 100%, comparable to those of the original assay (9).The study was conducted on isolates from an ongoing study that is evaluating the use of the GeneXpert MTB/RIF test (Xpert) in Lusaka, Zambia. Sputum samples were collected from suspected tuberculosis (TB) and confirmed TB patients attending routine services for whom Xpert detected TB or TB with rifampin resistance and from 10% of those for whom Xpert did not detect TB, for quality assurance, confirmation of rifampin resistance, and treatment monitoring purposes. The study had ethical approval from the University of Zambia Ethics Committee, and all patients provided written informed consent before submitting sputum samples for mycobacterial culture.Sputum specimens were decontaminated using the N-acetyl-L-cysteine (NALC)-NaOH method and were inoculated in a manual mycobacterial growth indicator tube (MGIT; BD) according to standard operating procedures (10, 11). All growth-positive tubes were subjected to Ziehl-Neelsen (ZN) staining, and the Capilia test was performed on all culture isolates confirmed to contain acid-fast bacilli (AFB). Capilia test-negative isolates were confirmed using the GenoType Mycobacterium Common Mycobacteria (GTM_CM) test (Hain Lifescience, Nehren, Germany). Further, isolates from patients with Mycobacterium tuberculosis/ Xpert-detected rifampin resistance were confirmed using the MTBDRplus assay as part of protocols for the ...

The performance of the Xpert© MTB/RIF and MTBDRplus assays for the detection of rifampicin resistant Mycobacterium tuberculosis was compared to culture-based drug susceptibility testing in 30 specimens with rifampicin-resistant and rifampicin-indeterminate Xpert MTB/RIF results collected between March 2012 and March 2014. Xpert MTB/RIF and MTBDRplus were 100% sensitive and 100% concordant for rifampicin resistance detection, but 3 of 13 samples (23%) positive for rifampicin resistance on Xpert MTB/RIF and MTBDRplus were negative for rifampicin resistance on mycobacteria growth indicator tube drug susceptibility testing. Specificity was 72% for Xpert MTB/RIF and 80% for MTBDRplus. Positive predictive value for Xpert MTB/RIF for multidrug resistant tuberculosis was 47.8% for new patients and 77.8% for previously treated patients; negative predictive value was 100% for both new and previously treated patients. The discordant rifampicin resistance test results indicate a need to fully characterise circulating rifampicin resistant Mycobacterium tuberculosis strains in Zambia and to inform the development of guidelines for decision-making in relation to diagnosis of drug-resistant tuberculosis.

ObjectivesTo evaluate the performance of point-of-care C-reactive protein (CRP) as a screening tool for tuberculosis (TB) using a threshold of 10 mg/L in both people living with HIV (PLHIV) and HIV-negative individuals and compare it to symptom screening using a composite reference for bacteriological confirmation of TB.MethodsProspective cross-sectional study.SettingA primary healthcare facility in Lusaka, Zambia.ParticipantsConsecutive adults (≥18 years) presenting for routine outpatient healthcare were enrolled. Of the 816 individuals approached to participate in the study, 804 eligible consenting adults were enrolled into the study, of which 783 were included in the analysis.Primary outcome measuresSensitivity, specificity, positive predictive value and negative predictive value (NPV) of CRP and symptom screening.ResultsOverall, sensitivity of WHO-recommended four-symptom screen (W4SS) and CRP were 87.2% (80.0–92.5) and 86.6% (79.6–91.8) while specificity was 30.3% (26.7–34.1) and 34.8% (31.2–38.6), respectively. Among PLHIV, sensitivity of W4SS and CRP was 92.2% (81.1–97.8) and 94.8% (85.6–98.9) while specificity was 37.0% (31.3–43.0) and 27.5% (22.4–33.1), respectively. Among those with CD4≥350, the NPV for CRP was 100% (92.9–100). In the HIV negative, sensitivity of W4SS and CRP was 83.8% (73.4–91.3) and 80.3% (69.5–88.5) while specificity was 25.4% (20.9–30.2) and 40.5% (35.3–45.6), respectively. Parallel use of CRP and W4SS yielded a sensitivity and NPV of 100% (93.8–100) and 100% (91.6–100) among PLHIV and 93.3% (85.1–97.8) and 90.0% (78.2–96.7) among the HIV negatives, respectively.ConclusionSensitivity and specificity of CRP were similar to symptom screening in HIV-positive outpatients. Independent use of CRP offered limited additional benefit in the HIV negative. CRP can independently accurately rule out TB in PLHIV with CD4≥350. Parallel use of CRP and W4SS improves sensitivity irrespective of HIV status and can accurately rule out TB in PLHIV, irrespective of CD4 count.

Background Combination of genotypic assays (Xpert MTB/ RIF and MTBDRplus (LiPA) would be a powerful tool to shorten the time for diagnosis of MDR tuberculosis (TB). However, the algorithm used for these assays in Zambia has not yet been implemented and the most widely used drug susceptibility testing (DST) method remains MGIT DST. Missed rifampicin resistance on the MGIT 960 system has been reported by several studies due to silent rpoB gene mutations. We report comparative observations made on the performance of Xpert, LiPA and MGIT DST methods for detection of rifampicin resistance (RR) at the ZAMBART Central Laboratory (ZCL). Methods Specimens were collected from consecutive patients with Xpert rifampicin resistance positive (RR+) or rifampicin resistance indeterminate (RRI) results at peripheral site laboratories for further testing at the ZCL. Each sample was tested using Xpert, LiPA and MGIT culture/DST. Results 30 patient samples were received and 17 were RR+, 8 were rifampicin-sensitive (RR-) and 5 were TB-negative by Xpert. All 17 RR+ on Xpert were RR+ on LiPA and all 8 Xpert RR -were sensitive on LiPA giving a 100% concordance for diagnosis of RR. Three isolates that were rifampicin sensitive by the MGIT system (Gold standard) were RR+ by both genotypic tests. Genotypic tests showed evidence of mutation in the codon 526 region of the rpoB gene for all the three isolates with discordant RR MGIT DST results. Xpert positive predictive value for Multidrug Resistance (MDR) TB was 62.5% and 81.2% compared to MGIT DST and LiPA, respectively. Conclusions There is need for Zambia to perform a full classification of rpoB mutations to determine the prevalence of silent mutations. This will optimise national guidelines for diagnosis of RR -and MDR-TB.