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

      Bonnet, M; Ramsay, A; Githui, W; Gagnidze, L; Varaine, F; Guerin, P J; Epicentre, Paris, France; Médecins Sans Frontières, Paris, France; Liverpool School of Tropical Medicine, Liverpool, United Kingdom; Centre for Respiratory Diseases Research, Kenya Medical Research Institute, Nairobi, Kenya (Infectious Diseases Society of America, 2008-06-01)
      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.
    • Evaluation of combined LED-fluorescence microscopy and bleach sedimentation for diagnosis of tuberculosis at peripheral health service level.

      Bonnet, M; Gagnidze, L; Guerin, P J; Bonte, L; Ramsay, A; Githui, W; Varaine, F; Epicentre, Paris, France. maryline.bonnet@geneva.msf.org (2011-05-31)
      Sputum microscopy is the only diagnostic for tuberculosis (TB) available at peripheral levels of health service in resource-poor countries. Its sensitivity is reduced in high HIV-prevalence settings. Sodium hypochlorite (NaOCl) specimen sedimentation prior microscopy and light-emitting diode (LED)-fluorescence microscopy (FM) can individually improve performance of microscopy. This study aimed to evaluate the performance of combined LED-FM and NaOCl sputum sedimentation for TB detection at peripheral level of health services.
    • Evaluation of FASTPlaqueTB to diagnose smear-negative tuberculosis in a peripheral clinic in Kenya

      Bonnet, M; Gagnidze, L; Varaine, F; Ramsay, A; Githui, W; Guerin, P J; Epicentre, Paris, France; Liverpool School of Tropical Medicine, Liverpool, UK; United Nations Children’s Fund/United Nations Development Programme/World Bank/World Health Organization Special Programme for Research and Training for Tropical Diseases (TDR), Geneva, Switzerland; Centre for Respiratory Diseases Research, Kenya Medical Research Institute, Nairobi, Kenya (2009-09-01)
      OBJECTIVE: To evaluate the performance and feasibility of FASTPlaqueTB in smear-negative tuberculosis (TB) suspects in a peripheral clinic after laboratory upgrading. DESIGN: Patients with cough > or=2 weeks, two sputum smear-negative results, no response to 1 week of amoxicillin and abnormal chest X-ray were defined as smear-negative suspects. One sputum sample was collected, decontaminated and divided into two: half was tested with FASTPlaqueTB in the clinic laboratory and the other half was cultured on Löwenstein-Jensen medium in the Kenyan Medical Research Institute. Test sensitivity and specificity were evaluated in all patients and in human immunodeficiency virus (HIV) infected patients. Feasibility was assessed by the contamination rate and the resources required to upgrade the laboratory. RESULTS: Of 208 patients included in the study, 56.2% were HIV-infected. Of 203 FASTPlaqueTB tests, 95 (46.8%) were contaminated, which interfered with result interpretation and led to the interruption of the study. Sensitivity and specificity were respectively 31.2% (95%CI 12.1-58.5) and 94.9% (95%CI 86.8-98.4) in all patients and 33.3% (95%CI 9.9-65.1) and 93.9% (95%CI 83.1-98.7) in HIV-infected patients. Upgrading the laboratory cost euro 20,000. CONCLUSION: FASTPlaqueTB did not perform satisfactorily in this setting. If contamination can be reduced, in addition to laboratory upgrading, its introduction in peripheral clinics would require further assessment in smear-negative and HIV co-infected patients and test adaptation for friendlier use.
    • Performance of LED-Based Fluorescence Microscopy to Diagnose Tuberculosis in a Peripheral Health Centre in Nairobi.

      Bonnet, M; Gagnidze, L; Githui, W; Guérin, P J; Bonte, L; Varaine, F; Ramsay, A; Epicentre, Paris, France. (PloS One, 2011-02)
      Sputum microscopy is the only tuberculosis (TB) diagnostic available at peripheral levels of care in resource limited countries. Its sensitivity is low, particularly in high HIV prevalence settings. Fluorescence microscopy (FM) can improve performance of microscopy and with the new light emitting diode (LED) technologies could be appropriate for peripheral settings. The study aimed to compare the performance of LED-FM versus Ziehl-Neelsen (ZN) microscopy and to assess feasibility of LED-FM at a low level of care in a high HIV prevalence country.
    • Performance of LED-Based Fluorescence Microscopy to Diagnose Tuberculosis in a Peripheral Health Centre in Nairobi.

      Bonnet, M; Gagnidze, L; Githui, W; Guérin, P J; Bonte, L; Varaine, F; Ramsay, A; Epicentre, France; Centre for Respiratory Diseases Research, Kenya Medical Research Institute, Kenya; Médecins Sans Frontières, France; UNICEF/UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases, World Health Organization, Switzerland (2011-02-18)
      Sputum microscopy is the only tuberculosis (TB) diagnostic available at peripheral levels of care in resource limited countries. Its sensitivity is low, particularly in high HIV prevalence settings. Fluorescence microscopy (FM) can improve performance of microscopy and with the new light emitting diode (LED) technologies could be appropriate for peripheral settings. The study aimed to compare the performance of LED-FM versus Ziehl-Neelsen (ZN) microscopy and to assess feasibility of LED-FM at a low level of care in a high HIV prevalence country.
    • Reducing the Number of Sputum Samples Examined and Thresholds for Positivity: An Opportunity to Optimise Smear Microscopy.

      Bonnet, M; Ramsay, A; Gagnidze, L; Githui, W; Guerin, P J J; Varaine, F; Epicentre, Paris, France. maryline.bonnet@geneva.msf.org (International Union Against TB and Lung Disease, 2007-09)
      SETTING: Urban health clinic, Nairobi. OBJECTIVE: To evaluate the impact on tuberculosis (TB) case detection and laboratory workload of reducing the number of sputum smears examined and thresholds for diagnosing positive smears and positive cases. DESIGN: In this prospective study, three Ziehl-Neelsen stained sputum smears from consecutive pulmonary TB suspects were examined blind. The standard approach (A), > or = 2 positive smears out of 3, using a cut-off of 10 acid-fast bacilli (AFB)/100 high-power fields (HPF), was compared with approaches B, > or = 2 positive smears (> or = 4 AFB/100 HPF) out of 3, one of which is > or = 10 AFB/100 HPF; C, > or = 2 positive smears (> or = 4 AFB/100 HPF) out of 3; D, > or = 1 positive smear (> or = 10 AFB/100 HPF) out of 2; and E, > or = 1 positive smear (> or = 4 AFB/100 HPF) out of 2. The microscopy gold standard was detection of at least one positive smear (> or = 4 AFB/100 HPF) out of 3. RESULTS: Among 644 TB suspects, the alternative approaches detected from 114 (17.7%) (approach B) to 123 cases (19.1%) (approach E) compared to 105 cases (16.3%) for approach A (P < 0.005). Sensitivity ranged between 82.0% (105/128) for A and 96.1% (123/128) for E. The single positive smear approaches reduced the number of smears by 36% compared to approach A. CONCLUSION: Reducing the number of specimens and the positivity threshold to define a positive case increased the sensitivity of microscopy and reduced laboratory workload.
    • Sputum, sex and scanty smears: new case definition may reduce sex disparities in smear-positive tuberculosis

      Ramsay, A; Bonnet, M; Gagnidze, L; Githui, W; Varaine, F; Guérin, P J; Liverpool School of Tropical Medicine, Liverpool, UK; Epicentre, Paris, France; Kenya Medical Research Institute, Nairobi, Kenya; Médecins Sans Frontières, Paris, France (2009-05-01)
      SETTING: Urban clinic, Nairobi. OBJECTIVES: To evaluate the impact of specimen quality and different smear-positive tuberculosis (TB) case (SPC) definitions on SPC detection by sex. DESIGN: Prospective study among TB suspects. RESULTS: A total of 695 patients were recruited: 644 produced > or =1 specimen for microscopy. The male/female sex ratio was 0.8. There were no significant differences in numbers of men and women submitting three specimens (274/314 vs. 339/380, P = 0.43). Significantly more men than women produced a set of three 'good' quality specimens (175/274 vs. 182/339, P = 0.01). Lowering thresholds for definitions to include scanty smears resulted in increases in SPC detection in both sexes; the increase was significantly higher for women. The revised World Health Organization (WHO) case definition was associated with the highest detection rates in women. When analysis was restricted only to patients submitting 'good' quality specimen sets, the difference in detection between sexes was on the threshold for significance (P = 0.05). CONCLUSIONS: Higher SPC notification rates in men are commonly reported by TB control programmes. The revised WHO SPC definition may reduce sex disparities in notification. This should be considered when evaluating other interventions aimed at reducing these. Further study is required on the effects of the human immuno-deficiency virus and instructed specimen collection on sex-specific impact of new SPC definition.