Evaluation of the Genotype® MTBDRplus assay as a tool for drug resistance surveys.

SETTING: A national tuberculosis (TB) drug resistance survey in Tanzania. OBJECTIVE: To compare the performance of the Genotype® MTBDRplus line-probe assay (LPA) on smear-positive sputum specimens with conventional culture and isoniazid (INH) plus rifampicin (RMP) drug susceptibility testing (DST). DESIGN: Mycobacterium tuberculosis isolates tested at the Tanzanian Central TB Reference Laboratory (CTRL) were submitted for quality assurance of phenotypic DST to its supranational reference laboratory (SRL), together with ethanol-preserved sputum specimens for LPA DST. RESULTS: Only 321 samples could be tested using LPA; of these, three were identified as being non-tuberculous mycobacteria using CTRL DST. Both tests had 269 sets with interpretable results. CTRL DST yielded almost the same number of interpretable results as LPA, with 90% concordance (κ = 0.612, P < 0.001). Five (1.9%) multidrug-resistant (MDR) strains, 46 (17.1%) resistant to INH only and 0 RMP only, were found by CTRL DST. For the LPA, these results were respectively 5 (1.9%), 26 (9.7%) and 2 (0.7%). With SRL DST as the gold standard, LPA was more accurate than CTRL DST for RMP, but missed almost half the INH-resistant samples. CONCLUSION: LPA applied directly on ethanol-preserved sputum specimens was similar to phenotypic DST in terms of yield of interpretable results. Although probably more accurate for RMP and MDR-TB, it appears to seriously underestimate INH resistance. Considering speed, easy and safe specimen transportation and low infrastructure requirements, LPA DST from sputum can be recommended for surveys in resource-poor settings.

National anti-tuberculosis drug resistance study in Tanzania.

OBJECTIVE: To assess the prevalence of anti-tuberculosis drug resistance in a national representative sample of tuberculosis (TB) patients in Tanzania according to recommended methodology. DESIGN: Cluster survey, with 40 clusters sampled proportional to size, of notified TB patients from all diagnostic centres in the country. RESULTS: The survey enrolled 1019 new and 148 retreatment patients. The adjusted prevalence of Mycobacterium tuberculosis strains resistant to any of the four first-line drugs in new patients was 8.3%, while the prevalence of multidrug-resistant TB (MDR-TB) was 1.1%. In retreatment patients, the crude prevalence for any resistance and for MDR-TB was respectively 20.6% and 3.9%. The prevalence of drug resistance did not differ in relapse patients compared to failure patients. These estimates are among the lowest in those African countries with an estimated level of drug resistance in the last 5 years. CONCLUSION: The low levels of drug resistance in Tanzania are likely due to a well performing TB control programme and the absence of noticeable involvement of the private sector in TB treatment.

Performance and acceptability of the FluoLED Easy module for tuberculosis fluorescence microscopy.

SETTING: Tuberculosis (TB) reference laboratory in Bangkok, Thailand, and two health centres in Dar es Salaam, Tanzania. OBJECTIVES: To assess the performance and user-friendliness of a light-emitting diode (LED) module (FluoLED Easy) for TB fluorescence microscopy (FM). DESIGN: Equivalence study vs. conventional FM in Bangkok using blinded re-reading; routine detection in the health centres in Dar es Salaam compared to Ziehl-Neelsen (ZN) over 2 years, with rechecking of FM smears. RESULTS: For 461 smears re-read, 99.1% concordance with conventional FM was obtained. FluoLED introduction caused a lasting increase in detection in the routine of each of the health centres by on average 20%. Blinded rechecking failed due to unreliable registration. Onsite rechecking of a convenience sample showed absence of false-positive results in one centre and confusion with artefacts that could have been avoided by more training in the other. LED FM was highly appreciated, with both laboratories refusing to revert to ZN as originally intended. CONCLUSIONS: A simple microscope with a FluoLED module can yield results equivalent to those of conventional FM. Low cost, technical appropriateness and excellent acceptance justify its use in low-income settings, contrary to classical systems. LED FM can lead to increased sensitivity, but for optimal yield good training and quality assurance remain essential requirements.

The quality of sputum smear microscopy diagnosis of pulmonary tuberculosis in Dar es Salaam, Tanzania.

This study was carried out to determine the rate of agreement or disagreement of microscopy reading and culture positivity rate among smear positixe and negative specimens between peripheral tuberculosis diagnostic centres (PDCs) and Central Reference luberculosis laboratory (CTRL). In this study 13 PDCs in Dar es Salaam, Tanzania were involved. Lot Quality Assurance Sampling (LQAS) method was used to collect 222 sputum smear slides. A total of 190 morning sputum specimens with corresponding slides were selected for culture. First readings were done by technicians at PDCs and thereafter selected slides and specimens were sent to CTRL for re-examination and culture. Culture results were used as a gold standard. Of 222 slides selected, 214 were suitable for re-examination. Percentage of agreement of smear reading between PDCs and CTRL was 42.9% and 100% for positive and negative slides, respectively. Measure of agreement (Kappa statistic) was 0.5, indicating moderate agreement. Of 190 samples cultured, percentage of agreement between smear reading from PDCs and CTRL was 37% and 88.9% for smear positive and negative slides, respectively. Kappa statistic was 0.3 indicating poor-fair agreements. Comparison of smear reading from PDCs with culture showed sensitivity of 36.9% and specificity of 88.9%. Comparison of smear readings from CTRL with culture results showed sensitivity of 95.6% and specificity of 98.6%. In conclusion there was inadequate performance in diagnosis of TB using smear microscopy among peripheral diagnostic centres in Dar es Salaam. This calls for immediate and rigorous measures to improve the quality of smear microscopy. It is therefore important to strengthen the capacity of laboratory personnel in smear microscopy techniques through supportive supervision and training.

Trend in HIV prevalence among tuberculosis patients in Tanzania, 1991-1998.

OBJECTIVE: To determine the trend in human immunodeficiency virus (HIV) prevalence among tuberculosis patients in Tanzania and estimate what proportion of the increase in notification rates between the surveys was directly attributable to HIV infection. METHODS: Consecutive tuberculosis patients were enrolled over 6-month periods in most regions. Demographic and clinical data were collected on standard forms and a single HIV ELISA test performed. Trends in tuberculosis incidence were estimated from regional notification data. RESULTS: Of 10612 eligible tuberculosis patients, 44% had HIV infection, compared with 32% in the previous survey. The largest increase was observed in the youngest birth cohorts, suggesting active HIV transmission. Approximately 60% of the increase in notification rates of smear-positive tuberculosis between surveys was directly attributable to HIV infection. CONCLUSION: The HIV epidemic has had a strong influence on tuberculosis incidence. However, since 1995, tuberculosis notification data have increased less steeply, AIDS notifications have gone down, and HIV prevalence in blood donors has not increased a great deal. Another survey among tuberculosis patients in 5 years' time may show whether the HIV epidemic in Tanzania has reached a maximum or steady state.

Diagnosis of tuberculosis in sputum negative patients in Dar es Salaam.

OBJECTIVE: To determine diagnostic criteria for tuberculosis among sputum smear acid fast bacilli negative patients with chronic cough, based on symptoms, signs and simple laboratory tests. DESIGN: A two-month prospective follow up study. SETTING: Muhimbili Medical Centre, Dar es Salaam, Tanzania. SUBJECTS: One hundred and seventy- eight consecutive patients admitted between 1st November, 1994 and 31st March, 1995 with chronic productive cough. MAIN OUTCOME MEASURES: Sputum smear acid fast bacilli (AAFB) negative with TB, discriminating ability of clinical and laboratory parameters. RESULTS: Forty three (24.2%) were sputum smear positive for acid fast bacilli (AAFB). In 90 (50.6%) patients, AAFB could be isolated in specimen other than sputum and in 45 (25.3%) no AAFB could be isolated. In a univariate analysis of all symptoms, signs and laboratory test results, cough of four or more weeks, haemoptysis, oral candidiasis, chest consolidation, pleural effusion, mid zone and upper zone chest x-ray opacities were significantly different between sputum AAFB negative TB and non TB patients. Discriminant analysis revealed six highly significant variables: Mantoux reaction, pleural effusion, Kaposi's lesion, cervical lymphadenopathy, matted lymph node, mid zone and upper zone CXR infiltrates. From these variables an equation was derived to calculate the probability that a sputum smear negative patient had tuberculosis. Then a scoring system was developed that classified correctly 84% of cases of sputum AAFB negative patients into tuberculosis or non tuberculosis. CONCLUSION: In sputum smear AAFB negative patient clinically suspected to have tuberculosis, Mantoux reaction, cervical lymphadenopathy, matted lymph nodes, absence of mid lower zone infiltration on CXR and presence of pleural effusion could be used for presumptive diagnosis, but they would not make a therapeutic trial unnecessary.

An epidemiological study of tuberculosis and HIV infection in Tanzania, 1991-1993.

OBJECTIVE: In Tanzania during the past 6 years reported tuberculosis (TB) cases have nearly doubled, with proportionately much greater increases in smear-negative and extrapulmonary cases compared with smear-positive cases. At the same time, HIV infection has become widespread throughout the country. This survey was undertaken in order to study the association of TB and HIV and to determine the impact of HIV on present and future TB cases in Tanzania. METHODS: The survey design provided for HIV testing of a representative country-wide sample of approximately one-sixth of all new and relapse cases registered between January 1991 and December 1993, with linkage to demographic, clinical and bacteriological data for these cases. HIV surveillance data were used for comparison purposes. RESULTS: A total of 6928 TB cases from all of the country's 20 mainland regions were tested. The overall HIV seroprevalence was 32%. Both crude and adjusted odds ratios (OR) for HIV infection were higher in women, those aged 25-44 years, urban residents, cases of smear-negative and extrapulmonary disease, and persons with a bacille Calmette-Guérin (BCG) vaccination scar. The age-and sex-adjusted relative risk for HIV infection in TB patients compared to blood donors in the same regions was 7.1 (95% confidence interval, 6.6-7.5), and was significantly higher among those aged 25-34 years. Of 3360 patients with bacteriological culture results 46% were culture-positive for Mycobacterium tuberculosis. Drug susceptibility tests were performed on 1164 isolates with the overall rate of drug resistance of 6.2%. Rates of initial resistance were low in both HIV-positive (4%) and HIV-negative (5.8%) patients. Rates of acquired resistance were higher (19% overall) and did not vary significantly by HIV serostatus. Initial combined resistance to both isoniazid and rifampicin was uncommon (0.4%) as was monoresistance to rifampicin (0.3%). CONCLUSIONS: The higher OR for women and young adults reflect the higher rates of HIV infection in those populations. The finding that smear-positive relapse cases were no more likely to have HIV infection than new smear-positive cases suggests that the treatment regimen for new cases is effective in HIV-associated TB. The low rates of both initial and acquired drug resistance in HIV-positive patients is further evidence of adequacy of treatment. The higher relative risk for HIV infection among patients aged 25-34 years suggests increased HIV-related TB transmission. Finally, it is estimated that approximately two-thirds of the increase in the rate of smear-positive tuberculosis in the country can be directly attributed to HIV infection.

PIP: The number of tuberculosis (TB) cases reported in Tanzania during the past six years has nearly doubled. Concurrently, HIV infection has become widespread throughout the country. This survey was conducted to study the association between TB and HIV, and to determine the impact of HIV upon present and future TB cases in the country. The survey design provided for HIV testing of a representative country-wide sample of approximately 17% of all new and relapse TB cases registered between January 1991 and December 1993. 6928 TB cases were tested from all of the country's mainland regions to find an overall HIV seroprevalence of 32%. Both crude and adjusted odds ratios for HIV infection were higher in women, those aged 25-44 years, urban residents, cases of smear-negative and extrapulmonary disease, and persons with a BCG vaccination scar. The age- and sex-adjusted relative risk for HIV infection in TB patients compared to blood donors in the same regions was 7.1, and was significantly higher among those aged 25-34 years. 46% of the 3360 patients with bacteriological culture results were culture-positive for Mycobacterium tuberculosis. Drug susceptibility tests were performed on 1164 isolates with the overall drug resistance rate of 6.2%. Rates of initial resistance were 4% among HIV-positive patients and 5.8% among HIV-negative patients. There was a 19% overall rate of acquired resistance which did not vary significantly by HIV serostatus. Initial combined resistance to both isoniazid and rifampicin was 0.4%; there was a 0.3% monoresistance to rifampicin. The authors estimate that approximately two-thirds of the increase in the rate of smear-positive TB in Tanzania can be directly attributed to HIV infection.