Bleach sedimentation: an opportunity to optimize smear microscopy for tuberculosis diagnosis in settings of high prevalence of HIV

BACKGROUND: The purpose of the study was to evaluate the performance and feasibility of tuberculosis diagnosis by sputum microscopy after bleach sedimentation, compared with by conventional direct smear microscopy, in a setting of high prevalence of HIV. METHODS: In a community-based study in Kenya (a population in which 50% of individuals with tuberculosis are infected with HIV), individuals with suspected pulmonary tuberculosis submitted 3 sputum specimens during 2 consecutive days, which were examined by blind evaluation. Ziehl-Neelsen-stained smears were made of fresh specimens and of specimens that were processed with 3.5% household bleach followed by overnight sedimentation. Two different cutoffs for acid-fast bacilli (AFB) per 100 high-power fields (HPF) were used to define a positive smear: >10 AFB/100 HPF and 1 AFB/100 HPF. Four smear-positive case definitions, based on 1 or 2 positive smears with the 1 AFB or 10 AFB cutoff, were used. RESULTS: Of 1879 specimens from 644 patients, 363 (19.3%) and 460 (24.5%) were positive by bleach sedimentation microscopy, compared with 301 (16.0%) and 374 (19.9%) by direct smear microscopy, with use of the 10 AFB/100 HPF (P < .001) and 1 AFB/100 HPF (P < .001) cutoffs, respectively. Regardless of the case definition used, bleach sedimentation microscopy detected significantly more positive cases than did direct smear microscopy: 26.7% (172 of 644) versus 21.7% (140 of 644), respectively, with the case definition of 1 positive smear and the 1 AFB/100 HPF cutoff (P < .001), and 21.4% (138 of 644) versus 18.6% (120 of 644), respectively, with the case definition of 1 positive smear and the 10 AFB/100 HPF cutoff (P < .001). Inter- and intrareader reproducibility were favorable, with kappa coefficients of 0.83 and 0.91, respectively. Bleach sedimentation was relatively inexpensive and was not time consuming. CONCLUSIONS: Bleach sedimentation microscopy is an effective, simple method to improve the yield of smear microscopy in a setting of high prevalence of HIV. Further evaluation of this method, under operational conditions, is urgently needed to determine its potential as a tool for tuberculosis control

Direct microscopy versus sputum cytology analysis and bleach sedimentation for diagnosis of tuberculosis: a prospective diagnostic study.

ABSTRACT: BACKGROUND: Diagnostic options for pulmonary tuberculosis in resource-poor settings are commonly limited to smear microscopy. We investigated whether bleach concentration by sedimentation and sputum cytology analysis (SCA) increased the positivity rate of smear microscopy for smear-positive tuberculosis. METHODS: We did a prospective diagnostic study in a Medecins Sans Frontieres-supported hospital in Mindouli, Republic of Congo. Three sputum samples were obtained from 280 consecutive pulmonary tuberculosis suspects, and were processed according to WHO guidelines for direct smear microscopy. The remainder of each sputum sample was homogenised with 2.6% bleach, sedimented overnight, smeared, and examined blinded to the direct smear result for acid-fast bacilli (AFB). All direct smears were assessed for quality by SCA. If a patient produced fewer than three good-quality sputum samples, further samples were requested. Sediment smear examination was performed independently of SCA result on the corresponding direct smear. Positivity rates were compared using McNemar's test. RESULTS: Excluding SCA, 43.2% of all patients were diagnosed as positive on direct microscopy of up to three samples. 47.9% were diagnosed on sediment microscopy, with 48.2% being diagnosed on direct microscopy, sediment microscopy, or both. The positivity rate increased from 43.2% to 47.9% with a case definition of one positive smear ([greater than or equal to]1 AFB/100 high power fields) of three, and from 42.1% to 43.9% with two positive smears. SCA resulted in 87.9% of patients producing at least two good-quality sputum samples, with 75.7% producing three or more. Using a case definition of one positive smear, the incremental yield of bleach sedimentation was 14/121, or 11.6% (95% CI 6.5-18.6, p=0.001) and in combination with SCA was 15/121, or 12.4% (95% CI 7.1-19.6, p=0.002). Incremental yields with two positive smears were 5/118, or 4.2% (95% CI 1.4-9.6, p=0.062) and 7/118, or 5.9% (95% CI 2.4-11.8, p=0.016), respectively. CONCLUSIONS: The combination of bleach sedimentation and SCA resulted in significantly increased microscopy positivity rates with a case definition of either one or two positive smears. Implementation of bleach sedimentation led to a significant increase in the diagnosis of smear-positive patients. Implementation of SCA did not result in significantly increased diagnosis of tuberculosis, but did result in improved sample quality. Requesting extra sputum samples based on SCA results, combined with bleach sedimentation, could significantly increase the detection of smear-positive patients if routinely implemented in resource-limited settings where gold standard techniques are not available. We recommend that a pilot phase is undertaken before routine implementation to determine the impact in a particular context

Identification of MDR-TB Beijing/W abd igter Ntcibacteruyn tyberculosis genotypes in Nairobi, Kenya

GesondheidswetenskappeMolekul�re Biologie & MensgenetikaPlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]

No increased prevalence of adrenocortical insufficiency in human immunodeficiency virus-associated tuberculosis

Setting: Acute medical wards, Kenyatta National Hospital, Nairobi, Kenya.Objective: To determine the prevalence of adrenocortical insufficiency in human immunodeficiency virus (HIV)-1 infected and non-infected patients with tuberculosis.Design: One hundred and seventy-four patients with proven tuberculosis (90 HIV-1 positive and 84 HIV-1 negative) were assessed for adrenocortical insufficiency with a 30 min synacthen stimulation test.Results: Fifty-one percent of those with pulmonary tuberculosis and 56% of those with extra-pulmonary tuberculosis had a subnormal cortisol response. However there was no statistically significant difference between the HIV-1 infected and non-infected patients in either group.Conclusion: While an impaired cortisol response is common in tuberculosis, it is no more prevalent in HIV-1 infected patients than non-infected patients with tuberculosis