Скачать презентацию Improving direct microscopy by overnight bleach sedimentation a Скачать презентацию Improving direct microscopy by overnight bleach sedimentation a

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Improving direct microscopy by overnight bleach sedimentation: a simple tool for peripheral Health 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 1 Epicentre, 2 Centre for Respiratory Diseases Research, Kenya Medical Research Institute, 3 Médecins Sans Frontières, 4 Liverpool School of Tropical Medicine, 5 TDR/WHO

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

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

Objective 1. To evaluate the diagnostic yield and feasibility of microscopy after overnight bleach Objective 1. To evaluate the diagnostic yield and feasibility of microscopy after overnight bleach sedimentation in a peripheral laboratory 1. To compare direct smear microscopy and overnight bleach sedimentation 1. Smear-positive patient detection 2. Smear-positive specimen detection 2. To evaluate practical aspects of overnight bleach sedimentation

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

Bleach 3. 5% Specimen liquifaction with bleach Overnight sedimentation on the bench Ziehl Neelsen Bleach 3. 5% Specimen liquifaction with bleach Overnight sedimentation on the bench Ziehl Neelsen microscopy on the sediment

Method q Case definitions § Smear-positive result: > 9 AFB/100 fields § Smear-positive patient Method q Case definitions § Smear-positive result: > 9 AFB/100 fields § Smear-positive patient § > 2 smear-positive results § > 1 smear-positive result q Analysis § Mc. Nemar test for comparison of matched data § Kappa coefficient for inter-reader and test-retest reliability (K >0. 8: very good reliability)

Results: Trial profile Total screened N= 788 Less than 15 years old =1 Impossibility 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

Patients’ characteristics q Mean age: 32. 5 years (SD 10. 3) q Sex ratio, Patients’ characteristics q Mean age: 32. 5 years (SD 10. 3) q Sex ratio, M/F: 0. 8 q Past TB history: 121 (18. 8%) q Intake of antibiotics in the last 2 weeks: 37 (5. 7%) q Production of 3 sputa: 614 (95. 3%)

Smear-positive TB patient detection q Definition of smear-positive patient : > 2 positive smears Smear-positive TB patient detection q 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

Smear-positive patient detection q Definition of smear-positive patient: > 1 positive smear (N=644) § Smear-positive patient detection q 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

Smear-positive patient detection q Bleach on 2 first sputa versus direct smear microscopy on Smear-positive patient detection q 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

Smear-positive specimen detection Smear-positive specimen detection

Practical aspects q Test reliability § Inter-observer Kappa 0. 81 (95% CI 0. 71 Practical aspects q Test reliability § Inter-observer Kappa 0. 81 (95% CI 0. 71 -0. 85) § Test-retest Kappa 0. 93 (95% CI 0. 89 -0. 95) q Mean duration of bleach sedimentation § Specimen bleaching: 18. 6 min § Overnight sedimentation: 16. 8 hours q 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

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

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

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

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

Smear-positive TB patient detection Smear-positive TB patient detection