Bonnet, Maryline

Gagnidze, L

Guithuy, W

Ramsay, A

Tajahmady, A

Varaine, F

English

MSF Field Research

DATA SOURCE DATA SOURCE
DISCUSSION DISCUSSION
2. CEA: EXCLUSION OF B1 AND B1+B2 WITHOUT TRANSPORT COST 2. CEA: EXCLUSION OF B1 AND B1+B2 WITHOUT TRANSPORT COST
ADDED VALUE OF BLEACH SEDIMENTATION MICROSCOPY  ADDED VALUE OF BLEACH SEDIMENTATION MICROSCOPY 
FOR DIAGNOSIS OF PULMONARY TUBERCULOSIS:  FOR DIAGNOSIS OF PULMONARY TUBERCULOSIS: 
A COST EFFECTIVENESS STUDY A COST EFFECTIVENESS STUDY
LIVERPOOL
SCHOOL OF
TROPICAL
MEDECINE
Maryline Bonnet1, Ayden Tajahmady2,Willie Githui3, Andrew Ramsay4, Laramie Gagnidze1, Francis Varaine5, Philippe J Guerin1
1 Epicentre, Paris, France, 2 Mission nationale d’expertise et d’audit hospitaliers, Paris, France, 3 Centre for Respiratory Diseases Research, Kenya Medical Research Institute, 
4 Liverpool School of Tropical Medicine (Present address: WHO/TDR, Geneva, Switzerland), 5 Médecins Sans Frontières, Paris, France 
BACKGROUND BACKGROUND
• Poor tuberculosis (TB) diagnostic in peripheral health clinics of high HIV prevalence countries 
– Smear microscopy too insensitive and no access to M tuberculosis culture
– No sensitive test expected to replace smear microscopy in a short time
• Overnight bleach sedimentation: simple and affordable method to optimise smear microscopy
– Meta-analysis: average of 23% increase of smear positive detection1
– 20-23% increase in a peripheral health clinic in Mathare (Kenya)2
• How to introduce the bleach sedimentation in current practices?
– Replacement / combination with direct smear microscopy?
– Impact on laboratory workload for setting with human resource crisis?
– Limitations of the method: fragility of smears, poor stability of bleach, delay of results by 1 day
1 Steingart KR, et al . Lancet Infect Dis 2006;6:664–74
2 Bonnet M, et al. Clin Infect Dis. 2008 Jun 1;46(11):1710-6
OBJECTIVES OBJECTIVES
To measure and compare the incremental cost per smear positive (SP) detected case of different 
approaches combining direct (D) and/or bleach (B) smear to diagnose TB among suspects in a 
peripheral health clinic of a high HIV prevalence country
METHODS METHODS
• Cost effectiveness analysis (CEA): Decision analytical model
– Health service provider perspective
• Including all potential smear microscopy approaches combining direct and/or bleach 
sedimentation on 2 sputum specimens examination
• After exclusion of approaches exclusively based on use of bleach sedimentation
– Addition of patients’ transport cost to reflect the difference of health clinic visits per approach
• Sensitivity analysis
– Variation of labour cost
– Variation of patients’ transport cost
• Field evaluation (diagnostic yield and feasibility) of smear microscopy after overnight sodium 
hypochlorite (NaOCl) sedimentation in Mathare, Nairobi (Kenya)1
• Sites and population
– Urban health clinic of Mathare, Nairobi (Kenya)
– 644 consecutive TB suspects presenting cough for more than 2 weeks
– 50% HIV co-infection
• Standardised NaOCl sedimentation method
– Same quantity of 3.5% local NaOCl to the specimen in 15ml conical tube
– Mixture homogenized using a vortex
– Overnight sedimentation on the bench at room temperature
• SP case definition
– 2 sputum specimens examination
• 1st on spot on the 1st day of consultation
• 2nd morning at home on 2nd day
– ≥ 1 smear positive result with ≥ 1AFB/100HPF
1 Bonnet M, et al. Clin Infect Dis. 2008 Jun 1;46(11):1710-6
SMEAR MICROSCOPY APPROACHES SMEAR MICROSCOPY APPROACHES
Approach Description
D1+D2 Standard: direct smear on 1st specimen and direct on 2nd specimen if the 1st smear is
negative
B1 Bleach smear on 1st specimen
B1+B2 Bleach smear on 1st specimen and bleach on 2nd if the 1st smear is negative
D1+B1 Direct smear on 1 st specimen and bleach on 1 st if the 1st smear is negative
B1+D2 Bleach smear on 1st specimen and direct smear on 2nd specimen
D1+B2 Direct smear on 1st specimen and bleach smear on 2nd if the 1st smear is negative
D1+B1+D2   Direct smear on 1st specimen, bleach on first and direct on 2nd if the 1st smear is
negative
D1+D2+B2   Direct smear on 1st specimen, direct on 2nd if 1st is negative and bleach on 2nd
spécimen if 2nd smear also negative
D1+B1+B2   Direct smear on 1st specimen, bleach on first if 1st smear negative and bleach on 2nd
specimen if 2nd smear also negative
B1+D2+B2   Bleach smear on 1st specimen and direct on 2nd specimen. Bleach smear on 2nd
spécimen if 2 previous smears are negative
Approaches based on the examination of only the 2nd specimen were not included
EFFECTIVENESS AND COSTS PARAMETERS EFFECTIVENESS AND COSTS PARAMETERS
• Effectiveness: smear positive case detection rate
• Costs
– Direct health service costs
• Labour cost
– Measure of time spent by laboratory technicians for specimen collection coaching, bleach 
specimen preparation and smear microscopy
– Base-case analysis: 600€ monthly salary
– Sensitivity cases analysis: 200€ and 1000€ per month
• Consumables and reagents based on the Kenyan market cost (2007)
• Increase by 0.2% and 1.9% to take into account unreadable D and B smear, respectively
• Micro costing approach 
– Patients’ transport cost estimates
• Base-case analysis: 1€/return
• Sensitivity analysis: 2€/return
RESULTS RESULTS
Smear Smear positive  positive detection detection rate per  rate per approach approach
Approach Smear positive detection rate Comparison with D1+D2 Visits
n % 95%CI P* n
D1+D2 135  21.0 17.9- 24.3 - 2.79
B1 150  23.3 20.1- 26.7 0.001 2
B1+B2 167  25.9 22.6- 29.5 <0.001 2.767
D1+B1 152  23.6 20.4- 27.1 <0.001 2
B1+D2 153  23.8 20.5- 27.2 <0.001 2.767
D1+B2 159  24.7 21.4- 28.2 <0.001 2.79
D1+B1+D2 153  23.8 20.5- 27.2 <0.001 2.764
D1+D2+B2 159  24.7 21.4- 28.2 <0.001 2.79
D1+B1+B2 167 25.9 22.6- 29.5 <0.001 2.764
B1+D2+B2 159 24.7 21.4- 28.2 <0.001 2.767
* McNemar test for matched data
1. CEA: ALL APPROACHES WITHOUT TRANSPORT COST 1. CEA: ALL APPROACHES WITHOUT TRANSPORT COST
B1
B1+B2
D1+B1
D1+B2
D1+D2
B1+D2
D1+B1+D2
D1+D2+B2
D1+B1+B2
B1+D2+B2
Not Dominated
Sensitivity analysis: no variation when using lower (200€/month) or higher (1000€/month) labour cost
Sensitivity analysis: no variation when using lower (200€/month) or higher (1000€/month) labour cost
3. CEA: ADDITION OF PATIENTS’ TRANSPORT COST 3. CEA: ADDITION OF PATIENTS’ TRANSPORT COST
• All approaches: B1 and B1+B2 most cost-effective approaches
• Exclusion of B1 and B1+B2: variation of results according to transport costs
Base-case analysis (1€ per return) Sensitivity-case analysis (2€/return)
1.5
2
2.5
3
3.5
4
4.5
0.2 0.21 0.22 0.23 0.24 0.25 0.26 0.27
Effectiveness
C
o
s
t
• A simple decision analytical model can give informative programmatic information
• Robust model 
– Using observed and published data collected in a peripheral health clinic in a high HIV prevalence country
– Use of micro costing approach
– Not sensitive to variation of labour cost
• B1 and B1+B2 best approaches based on our model 
• Variability of bleach quality and fragility of smears: CEA after exclusion of B1 and B1+B2
– D1+B2 best option - But most patients will only get results on 3rd day
– D1+B1 good alternative - Would require a good specimen collection (1 specimen) 
LIMITATIONS LIMITATIONS
CONCLUSIONS CONCLUSIONS
• Absence of patient’s cost perspective despite the estimates of transport costs
• Doesn’t reflect the risk of patients’ drop out during smear microscopy 
4.5% in the study conditions of Mathare
• Choice of approach based on different criteria
– Laboratory experiences in using bleach microscopy 
– TB program priority between detection and cost
– Patients’ access to smear microscopy services
• 4 possible scenarios (see table next)
• Improvement of the model using routine 
program data
Scenarios Possibility to use  Program  Access to health Best 
only B approach priority care services approach
1 Yes Cost Indifferent B1
2 Yes Detection Indifferent B1+B2
3 No Indifferent Bad D1+B1
4 No Indifferent Good D1+B2
D1+B1
D1+B2
4.5
5
5.5
6
6.5
7
7.5
0.2 0.21 0.22 0.23 0.24 0.25 0.26 0.27
Effectiveness
C
o
s
t
D1+B1
D1+B2
D1+D2
B1+D2
D1+B1+D2
D1+D2+B2
D1+B1+B2
B1+D2+B2
Not Dominated
D1+B1
6.5
7
7.5
8
8.5
9
9.5
10
0.2 0.21 0.22 0.23 0.24 0.25 0.26 0.27
Effectiveness
C
o
s
t
Maryline Bonnet (Epicentre) 
Rue de Lausanne 78, CH-1211 Genève 21
maryline.bonnet@geneva.msf.org
Costs (€ 2007)
Base- case analysis Sensitivity analysis
200 € 1000€
Labour
Reagents & 
consumables Total
Total + 
transport Labour Total Labour Total
Total + 
transport 
D1+D2 1.76 0.95 2.70 2.79 0.59 1.53 2.93 3.88 5.58
B1 1.22 0.79 2.01 2 0.41 1.20 2.03 2.82 4
D1+B1 1.84 1.10 2.94 2 0.61 1.71 3.07 4.17 4
D1+B2 1.84 1.17 3.01 2.79 0.61 1.78 3.07 4.24 5.58
B1+D2
2
1.83 1.21 3.03 2.77 0.61 1.81 3.05 4.25 5.53
D1+B1+D2 2.45 1.51 2.93 2.77 0.82 1.70 4.09 4.15 5.53
B1+B2 1.92 1.41 3.33 2.77 0.64 2.05 3.19 4.61 5.53
D1+D2+B2 2.48 1.51 3.96 2.79 0.83 2.33 4.14 5.60 5.58
D1+B1+B2 2.54 1.72 4.00 2.77 0.85 2.35 4.23 5.65 5.53
B1+D2+B2 2.52 1.75 4.25 2.77 0.84 2.56 4.20 5.94 5.53
2.5
3
3.5
4
4.5
0.2 0.21 0.22 0.23 0.24 0.25 0.26 0.27
Effectiveness
C
o
s
t
D1+B1
D1+B2
D1+D2
B1+D2
D1+B1+D2
D1+D2+B2
D1+B1+B2
B1+D2+B2
Not Dominated
B1+B2
B1
D1+B2

Added value of bleach sedimentation microscopy for diagnosis of pulmonary tuberculosis: cost-effectiveness study

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