Van Deun A

Fluorescein diacetate vital staining allows earlier diagnosis of rifampicin-resistant tuberculosis.

SETTING Damien Foundation Project, Bangladesh. OBJECTIVE To evaluate sputum smear fluorescein diacetate (FDA) vital staining to predict culture-defined failure and rifampicin (RMP) resistance. DESIGN A retrospective, operational study. RESULTS A total of 1633 episodes of auramine smear-defined late conversion and failure could be evaluated (respectively 640 and 584 on first treatment and 185 and 224 on retreatment). Negative FDA was 95% predictive of negative culture in patients on first treatment, while its positive predictive value was around 95% during retreatment. The predictive value of a positive (not scanty) result for RMP resistance or environmental non-tuberculous mycobacteria (NTM) was at least 90%, except in late converters on first-line treatment; a negative result was over 95% exclusive of the same except in retreatment failures. FDA correctly identified 88-98% of all RMP resistance. CONCLUSIONS FDA staining increased the proportion of tuberculosis patients put on second-line treatment without receiving the standard first-line retreatment regimen. In our setting, with excellent microscopy, late case presentation and low resistance prevalence, it proved indispensable for efficient culture and referrals of early suspects for rapid drug susceptibility testing (DST). In other settings with low prevalence of NTM and difficult access to accurate and rapid DST, FDA-positive failures might even be considered for immediate start of second-line treatment.

Extension of the intensive phase reduces relapse but not failure in a regimen with rifampicin throughout.

SETTING Damien Foundation tuberculosis (TB) control projects in Bangladesh. OBJECTIVE To assess the effectiveness of extending the intensive phase (P1) of treatment by 1 month for patients who are smear-positive after 2 months of a 6-month regimen containing rifampicin (RMP) throughout. DESIGN Prospective operational study randomising P1 extension for new smear-positive cases with any number of acid-fast bacilli in the 2-month smear (2M+). Smear-defined failures and relapses underwent culture and drug susceptibility testing in addition to DNA sequencing of the rpoB gene before and after treatment. RESULTS Of 16,708 patients evaluated, 12,967 were smear-negative at 2 months (2M-); 1871 and 1870 2M+ were randomised to no extension or extension. Respectively 0.3% (95%CI 0.2-0.4), 1.2% (95%CI 0.7-1.8) and 2.0% (95%CI 1.4-2.8) smear- and culture-positive failures, and 1.2% (95%CI 1.0-1.4), 2.6% (95%CI 1.9-3.4) and 0.9% (95%CI 0.5-1.4) relapses were detected. Extension significantly reversed the relative risk (RR) of relapse of 2M+ vs. 2M- patients from 2.2 (95%CI 1.6-3.0) to 0.7 (95%CI 0.4-1.2). The RR for failure remained high, at 7.3 (95%CI 4.7-11.5) with and 4.2 (95%CI 2.5-7.2) without extension. More multi-drug resistance was found after extension, but acquired RMP resistance was similar in all arms. The fair sensitivity of the 2-month smear for failure or relapse (40%) was offset by a very low positive predictive value (3%). CONCLUSIONS Extension of P1 is very inefficient with this 6-month regimen. Operational research should define appropriate algorithms allowing an earlier switch to the next higher regimen for those in need, using follow-up smears for screening.

Anti-tuberculosis drug resistance in Bangladesh: reflections from the first nationwide survey.

OBJECTIVE To determine the prevalence of tuberculosis (TB) drug resistance in Bangladesh. DESIGN Weighted cluster sampling among smear-positive cases, and standard culture and drug susceptibility testing on solid medium were used. RESULTS Of 1480 patients enrolled during 2011, 12 falsified multidrug-resistant TB (MDR-TB) patients were excluded. Analysis included 1340 cases (90.5% of those enrolled) with valid results and known treatment antecedents. Of 1049 new cases, 12.3% (95%CI 9.3-16.1) had strains resistant to any of the first-line drugs tested, and 1.4% (95%CI 0.7-2.5) were MDR-TB. Among the 291 previously treated cases, this was respectively 43.2% (95%CI 37.1-49.5) and 28.5% (95%CI 23.5-34.1). History of previous anti-tuberculosis treatment was the only predictive factor for first-line drug resistance (OR 34.9). Among the MDR-TB patients, 19.2% (95%CI 11.3-30.5; exclusively previously treated) also showed resistance to ofloxacin. Resistance to kanamycin was not detected. CONCLUSION Although MDR-TB prevalence was relatively low, transmission of MDR-TB may be increasing in Bangladesh. MDR-TB with fluoroquinolone resistance is rapidly rising. Integrating the private sector should be made high priority given the excessive proportion of MDR-TB retreatment cases in large cities. TB control programmes and donors should avoid applying undue pressure towards meeting global targets, which can lead to corruption of data even in national surveys.

In reply to 'Can LED fluorescence microscopy replace Ziehl-Neelsen microscopy in tuberculosis detection?'.

Ziehl-Neelsen (ZN) acid-fast bacilli (AFB) microscopy, which detects only about 50% of pulmonary tuberculosis patients in the community, is the cornerstone worldwide for the diagnosis of tuberculosis, as, apart from other constraints, it is infl uenced by the laboratory workload, stain quality and light microscope conditions in the fi eld. In comparison to ZN microscopy, conventional (mercury vapour lamp) fl uorescence microscopy (CFM), based on auramine phenol staining, can detect approximately 5–10% more AFB positive smears.1 However, CFM is used only in specialised laboratories and not in peripheral health institutions due to the requirement for expensive mercury vapour lamps and darkroom facilities. The light emitting-diode (LED) microscope, with its inexpensive, long-life LED lamps, is a boon to mycobacteriologists. The LED microscope can be housed and slides examined in an ordinary, well-lit room. Its major advantage is the ease of examination with 40×/20× objectives. Laboratory technicians (LTs) feel less fatigue on examining the slides, thus increasing the chances of AFB detection in paucibacillary samples. The World Health Organization recently recommended both the use of LED FM and replacing ZN microscopy in a phased manner. However, this gives rise to the following issues: 1) less experienced LTs are likely to commit false-positive errors,2 as impurities in auramine stains and artefacts such as blood3 in the sputum will fl uoresce like AFB; 2) detection of at least three AFB in a smear is likely to be highly confi rmative of culture-positive TB;4 3) AFB damaged by anti-tuberculosis drugs during treatment stain better with auramine than carbol fuchsin;5 4) positive smears are not checked before reporting the results in the fi eld; and 5) there is a paucity of knowledge about the adequacy of training on LED FM and on the quality of FM reporting in programmatic conditions: doubtful smears encountered with LED FM should be restained by ZN and verifi ed until the technicians are fully familiar with LED FM microscopy.

Sputum bacterial load predicts multidrug-resistant tuberculosis in retreatment patients: a case-control study.

BACKGROUND Rapid and effective diagnosis of multidrug-resistant tuberculosis (MDR-TB) is an essential component of global tuberculosis (TB) control, but most MDR-TB cases are still not diagnosed. OBJECTIVE To assess whether patient sputum bacterial load can be used to identify patients at increased risk of MDR-TB. METHODS We used a case-control study and multivariable logistic regression models to investigate associations between MDR-TB and sputum bacterial load, as measured by semi-quantitative microscopy and automated time to detection (TTD) of liquid culture. We assessed data from retreatment TB patients with MDR-TB (cases) and from those without MDR-TB (controls) at a reference laboratory in Cameroon. RESULTS MDR-TB was associated with a smear microscopy grade of 3+ (OR 21.9, 95%CI 6.2-76.8) or 2+ (OR 10.8, 95%CI 2.9-40.7), compared to a result of 1+, scanty or smear-negative among 80 MDR-TB cases and 521 controls. MDR-TB was associated with automated TTD of ⩿160 h (OR 2.2, 95%CI 1.1-4.7) compared to >160 h among a subpopulation of 47 cases and 350 controls. CONCLUSIONS A higher sputum bacterial load is associated with MDR-TB in retreatment patients in Cameroon.