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TB diagnosis in peripheral health care centres

Improving direct microscopy by overnight bleach sedimentation: a simple tool for peripheral Health Centres. Maryline Bonnet 1 , Laramie Gagnidze 1 , Willie Githui 2 , Francis Varaine 3 , Andrew Ramsay 4,5 , Philippe J Guerin 1

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TB diagnosis in peripheral health care centres

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  1. Improving direct microscopy by overnight bleach sedimentation: a simple tool for peripheral Health Centres Maryline Bonnet1, Laramie Gagnidze1, Willie Githui2, Francis Varaine3, Andrew Ramsay4,5, Philippe J Guerin1 1Epicentre, 2Centre for Respiratory Diseases Research, Kenya Medical Research Institute, 3Médecins Sans Frontières, 4Liverpool School of Tropical Medicine, 5TDR/WHO

  2. TB diagnosis in peripheral health care centres • Ziehl-Neelsen Direct Smear microscopy • Only available tool in most settings • 50% sensitivity • No new test expected in near future • Improvement of smear microscopy • Sputum collection (e.g. sputum induction) • Sputum processing (e.g. sputum concentration) • Staining and reading (e.g. fluorescence microscopy)

  3. Rationale • Sodium hypochlorite (“household bleach”) with overnight sedimentation • Encouraging results • Could be implemented in any setting • Still no recommendations due to study limitations

  4. Objective • To evaluate the diagnostic yield and feasibility of microscopy after overnight bleach sedimentation in a peripheral laboratory • To compare direct smear microscopy and overnight bleach sedimentation • Smear-positive patient detection • Smear-positive specimen detection • To evaluate practical aspects of overnight bleach sedimentation

  5. Method • Population • Mathare, Nairobi • High HIV prevalence • > 15 years, pulmonary TB suspects (cough > 2 weeks) • Consecutive sampling • Procedure • Collection of 3 sputa in 2 days • Hot Ziehl Neelsen method

  6. Bleach 3.5% Specimen liquifaction with bleach Overnight sedimentation on the bench Ziehl Neelsen microscopy on the sediment

  7. Method • Case definitions • Smear-positive result: > 9 AFB/100 fields • Smear-positive patient • > 2 smear-positive results • > 1 smear-positive result • Analysis • McNemar test for comparison of matched data • Kappa coefficient for inter-reader and test-retest reliability (K >0.8: very good reliability)

  8. Results: Trial profile Total screened N= 788 Less than 15 years old =1 Impossibility to produce sputum = 7 Cough < 2 weeks = 20 ICF not signed =63 Other =1 Included N= 696 52 no sputum Analysed N= 644 patients

  9. Patients’ characteristics • Mean age: 32.5 years (SD 10.3) • Sex ratio, M/F: 0.8 • Past TB history:121 (18.8%) • Intake of antibiotics in the last 2 weeks: 37 (5.7%) • Production of 3 sputa: 614 (95.3%)

  10. Smear-positive TB patient detection • Definition of smear-positive patient : > 2 positive smears (N=621) • 121 (19.5%) with bleach method compared to 105 (16.9%) with direct smear method, p=0.02 • 16 (15.2%) additional patients detected with bleach method • 4 (3.8%) missed cases

  11. Smear-positive patient detection • Definition of smear-positive patient: > 1 positive smear (N=644) • 138 (21.4%) with bleach method compared to 120 (18.6%) with direct smear method, p=0.001 • 18 (15.0%) additional patients detected with bleach method • 1 (0.8%) missed case

  12. Smear-positive patient detection • Bleach on 2 first sputa versus direct smear microscopy on 3 sputa (N= 644) • Definition of smear-positive patient > 1 positive smear • 133 (20.7%) with bleach method compared to 120 (18.6%) with direct smear method, p=0.01 • 18 (13.5%) additional patients detected with bleach method • 5 (4.2%) missed cases

  13. Smear-positive specimen detection

  14. Practical aspects • Test reliability • Inter-observer Kappa 0.81 (95% CI 0.71-0.85) • Test-retest Kappa 0.93 (95% CI 0.89-0.95) • Mean duration of bleach sedimentation • Specimen bleaching: 18.6 min • Overnight sedimentation: 16.8 hours • Mean duration of Ziehl-Neelsen method • Smearing & drying: 52.9 min versus 21.4 min • Staining: 45.0 min versus 47.1 min • Reading: 3.5 min with both methods

  15. Discussion • Study strengths • Prospective and controlled • Outpatient suspected TB cases in peripheral clinic • Standardised concentration method • Practical aspects • Reliability data • Study limitations Absence of comparison to the culture Gold Standard

  16. Advantages & disadvantages of the bleach method • Disadvantages • Risk of artefacts • Fragile smears • Delay in diagnosis • No standard bleach quality • Advantages • Signifiant increase of TB patient detection • Good reliability • Ease of use • Inexpensive • Bleach readily available

  17. Conclusions • Effective, simple and affordable • Further research needed • Best strategy based on cost-effectiveness analysis • Feasibility in routine program conditions • Overnight BS and fluorescence microscopy • Shorter sedimentation time

  18. Acknowledgements • Médecins Sans Frontières, study promotor • Stéphanie Charrondière • Tom, Purity, Ali, Andrew and Lucy • The team in Blue House • The team in the Mycobacteriological Laboratory, KEMRI • The Kenyan National TB Control Program

  19. Smear-positive TB patient detection

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