Detection of multidrug-resistant tuberculosis from stored DNA Samples: A multicenter study.

Background: In low-income countries, rapid detection of tuberculosis (TB) drug resistance is often restricted by the difficulties of transporting and storing sputum samples from remote health centers to the reference laboratories where molecular tests are available. The aim of this study was to evaluate the performance of four transport and storage systems for molecular detection of rifampicin (RIF) and isoniazid (INH) resistance. Methods: This was a multicenter study. Molecular detection of RIF and INH resistance was performed directly from smear-positive TB sputa spotted on a slide, FTA card, GenoCard, and ethanol using the Genotype MTBDRplus assay. The performance of the DNA extraction method from each storage support to detect drug resistance was assessed by calculating their sensitivity and specificity compared to the phenotypic method. Results: From all sites, the overall sensitivity and specificity for RIF-resistance detection was 88% and 85%, respectively, for slides, 86% and 92%, respectively, for GenoCard, 87% and 89%, respectively, for FTA card, and 88% and 92%, respectively, for ethanol. For INH-resistance detection, the overall sensitivity and specificity was 82% and 90%, respectively, for slides, 85% and 96%, respectively, for GenoCard, 86% and 92%, respectively, for FTA card, and 86% and 94%, respectively, for ethanol. Conclusion: Smear slides and filter cards showed to be very useful tools to facilitate DNA extraction from sputum samples with the potential to accelerate the detection of drug resistance in remote areas.

Evaluation of the Xpert MTB/RIF assay for the diagnosis of smear-negative pulmonary and extrapulmonary tuberculosis in Madagascar.

OBJECTIVE: To evaluate the feasibility of the implementation of a commercial rapid molecular diagnostic test (Xpert MTB/RIF) for the routine diagnosis of smear-negative or extrapulmonary tuberculosis (TB) and its diagnostic accuracy, and to assess HIV prevalence in a real-life setting in Madagascar. This study was set in a tertiary care hospital in Madagascar. METHODS: A prospective cohort study was conducted of all consecutive cases with suspected smear-negative and/or extrapulmonary TB over a 2-year period. Cases were classified as proven, probable, or possible TB cases, or as having an alternative diagnosis. RESULTS: Of the 363 patients included, 183 (50.4%) had suspected smear-negative pulmonary TB and 180 (49.6%) had suspected extrapulmonary TB. For proven cases, the sensitivity, specificity, positive and negative predictive values of Xpert MTB/RIF were 82.4%, 98.8%, 98.3%, and 86.6%, respectively; for proven and probable cases grouped together, these values were 65%, 98.8%, 98.5%, and 64%, respectively. The diagnostic accuracy was slightly lower for extrapulmonary TB compared to smear-negative pulmonary TB. The prevalence of HIV infection was 12.1%, but almost half of these cases did not have TB (alternative diagnosis group). CONCLUSIONS: The implementation of a rapid diagnosis programme for TB in a resource-poor setting is feasible. The performance of the Xpert-MTB/RIF was remarkable in this difficult-to-diagnose population. HIV prevalence in this study was much higher than the prevalence reported in the general population in Madagascar, in patients with TB and patients with conditions other than TB.

First national survey of Mycobacterium tuberculosis drug resistance, Madagascar, 2005-2006.

SETTING: A national survey of Mycobacterium tuberculosis resistance was conducted for the first time in Madagascar between October 2005 and July 2007. OBJECTIVE: To determine resistance rates among new and previously treated cases of pulmonary tuberculosis. METHODS: In a cluster sampling representative of the general population of the country, 1275 smear-positive tuberculosis patients recruited at 34 sites, 926 new patients and 87 previously treated patients underwent drug susceptibility testing against rifampicin (RMP), isoniazid (INH), streptomycin and ethambutol on Löwenstein-Jensen medium using the indirect proportion method. RESULTS: Resistance among new cases was 6.5% (95%CI 4.9-8) and among previously treated cases it was 11.5% (95%CI 4.8-18.2). Monoresistance among new cases was 5.8% (95%CI 4.2-7.3), mainly to INH (3.7%). Multiresistance to INH and RMP was 0.2% (95%CI 0-0.5) among new cases and 3.4% (95%CI 0-7.2) among previously treated cases. No significant difference was noted with regard to sex or age. CONCLUSION: The rates of resistance among new and previously treated cases remain relatively low in Madagascar.

Bacteriological follow-up of tuberculosis treatment: a comparative study of smear microscopy and culture results at the second month of treatment.

SETTING: Significance of a positive bacillary examination of sputum at 2 months of treatment in relation to the viability of the bacilli and the final treatment result. OBJECTIVE: To compare the results of smear microscopy and sputum culture at the second month of tuberculosis treatment and to follow the progress of the patients. METHODS: Follow-up of 297 patients with smear-positive pulmonary tuberculosis in Madagascar, 152 of whom were smear-positive at 2 months of treatment and 145 smear-negative. The number of bacilli was recorded, as were the culture results and the final outcome of treatment. RESULTS: Among the 152 patients who were smear-positive at the second month, 77 (51%) were culture-negative; there were 12 (8%) treatment failures and four relapses (4.6%). Among the 145 smear-negative patients, 22 (15%) were culture-positive, of which one was a treatment failure (1%). CONCLUSION: The majority of failures and relapses were observed in the group of smear-positive patients. It is important to reinforce the surveillance of these patients in order to reduce the number lost to follow-up. Furthermore, a positive smear microscopy at the end of the second month is not sufficiently specific for early identification of treatment failures. It is preferable to wait until the fifth month, as the great majority of patients who are positive at 2 months achieve cure. The treatment strategy currently recommended in Madagascar is satisfactory.

Validity of intradermal tuberculin testing for the screening of bovine tuberculosis in Madagascar.

A sample survey with the objective of determining the prevalence of bovine tuberculosis by means of an intradermal tuberculin test was conducted in Madagascar and it was found that the prevalence rate varied from 0-30% by veterinary district. In order to estimate the true prevalence, the validity of the test was investigated by assessing its sensitivity and specificity in two groups of animals from two different regions, which were destined for slaughter. In the first group where the probability of non-infected animals should have been the highest, sensitivity was estimated at 0.52 (n = 21) and specificity at 0.99 (n = 79). In the second group selected on the basis of apparent ill health of the animals in a high-prevalence bovine tuberculosis area, sensitivity was estimated at 0.8 (n = 10) and specificity at 1 (n = 12). The results obtained from both groups of cattle were not combined for statistical purposes because the sensitivity of the skin test seemed to fluctuate in relation to the chronicity of the disease. These fluctuations are discussed. However, since the first group of zebu cattle was more representative of the cattle population across the country as a whole, its results were retained as operational parameters for further screening.

45/47 kilodalton (APA) antigen capture and antibody detection assays for the diagnosis of tuberculosis.

SETTING: APA complex (45/47 kDa) is an antigen specifically excreted by Mycobacterium tuberculosis and could therefore be a good candidate for diagnosis. OBJECTIVES: To develop three APA immunocapture ELISA assays using monoclonal antibodies (Mabs) and one IgG anti-APA ELISA test, and to determine their usefulness for the diagnosis of tuberculosis in Madagascar. DESIGN: For the Ag assays, 23 negative sputum and serum samples and 64 pairs of sputum and serum from active smear-positive patients (PTM+) were tested. For antibody assay, 116 negative controls, 143 PTM+ and 54 extra-pulmonary tuberculosis patients were tested. RESULTS: The sensitivities of the APA antigen detection assays were low (less than 40%) for a specificity of 95.6%, using either monoclonal antibodies or clinical specimens. The anti-APA serology was more sensitive (76.9% for PTM+ patients) but less specific (73.2%). Due to their poor predictive values, these tests cannot be recommended for the routine diagnosis of tuberculosis in Madagascar.

Predictive values of the ICT Tuberculosis test for the routine diagnosis of tuberculosis in Madagascar.

The rapid commercialised ICT Tuberculosis test has been tested in Madagascar for the diagnosis of smear-positive pulmonary (SM+) and extra-pulmonary tuberculosis (EPT), using microscopy, culture and histopathology as reference tests. Specificity was 83.3% and sensitivity 68.2% for SM+ patients and 65.2% for EPT patients. With a prevalence of 22.2% for SM+ patients and 52.4% for confirmed EPT among consulting patients in the National Reference Laboratory, the ICT Tuberculosis assay was not sufficiently predictive for application in the tuberculosis control programme.

Anti-tuberculosis drug resistance in Madagascar in 1994-1995.

SETTING: A new tuberculosis control programme has been implemented in Madagascar since 1991. A survey on Mycobacterium tuberculosis resistance to the major drugs was conducted between August 1994 and December 1995. OBJECTIVE: To determine primary and acquired resistance in pulmonary tuberculosis patients in four main cities. DESIGN: Were included 401 randomly sampled new smear positive patients (36.2% of declared new patients) and 137 recurrent cases (72.9% of declared cases) from 8 centres. Drug susceptibility testing was performed on Löwenstein Jensen medium according to the proportion method. RESULTS: The male to female ratio was 1.35:1 in new patients (age range 11-74 years) and 1.98:1 in recurrent patients (age range 16-76 years). The primary resistance rate to any drug was 20% (95% Confidence Interval [CI] 16-23) and the acquired resistance rate 40% (95% CI 32-48, P < 2.10(-7). Primary resistance to one drug was 18% (95% CI 15-22), mainly attributable to streptomycin resistance (14.5%). Multidrug resistance (MDR) to isoniazid and rifampicin was 0.25% (95% CI 0-0.7) for primary resistance and 5% (95% CI 2.6-10.6) for secondary resistance. No difference was observed between sexes or ages. CONCLUSION: This survey conducted in big cities gives a very negative picture of resistance in Madagascar.