implementation of thin layer agar for mycobacterium culture in rural kenya médecins sans...
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Implementation of Thin Layer Agar for Mycobacterium culture in rural Kenya
Médecins Sans Frontières
Context
MSF support in the HospitalSince 2000
TB program
ART program
Integrated TB/HIV care
TB culture laboratory in 2007
MSF support in the peripheryMobile clinic to 3 health centres
Supply drugs 6 month regimen
Homa Bay District Rural area 350,000 habitants 30% HIV prevalence
Context
HIV patients 13,000 active patients
on care 10,000 active patients
on ART
TB patients 1,500 new TB cases/year in District 400 new TB cases in Chest Clinic 80% HIV/TB co-infected
Methods
Mycobacterium culture laboratory Techniques: Thin Layer Agar, Lowenstein-Jensen Routine activity since November 2007
Patients targeted Patients with cough >2 weeks and at least 2
negative sputum smear microscopy
Retrospective study
Period of the study: 15th Nov 07 to 25th July 08
Methods
TLA technique: Solid culture (7H11)
Petri dish (2 parts: 1 normal media; 1 with PNB)
Incubator CO2
Reading with microscope
Why this technique was chosen? Less logistics, maintenance, technical problems
Lower cost
Solid culture – less contamination expected, bio-safety
Comparison Mycobacterium culture techniques
LJ TLA MGIT MODS
Medium Solid Solid Liquid Liquid
Manual/Automated M M A M
Equipment/Maintenance + + +++ ++
Time to positive (days) 25 10 9 7
Sensitivity*
- Smear + 90 94 93
- Smear – 71 89 94
Cost (USD) 0.14 0.29 3.00 0.77
DST simultaneous No Yes No Yes
* Int J Tuberc Lung Dis 10 (6):613-619, 2006. Robledo et al
Results
Culture result available in 365 patients:
50% negative, 31% positive, 19% contaminated
56% of culture positive had not started treatment
Out of the 63 patients traced: 46% found and started on treatment 11% found and referred to the closest TB site 16% had died 13% could not be found 14% were still being traced
Results
Patients missed through clinical algorithm and
started on treatment after culture: 29 patients = 3.5 patients per month
Patients diagnosed through clinical algorithm: 265 = 31.9 patients per month
Proportion of TB patients diagnosed through
culture: 10.9%
Average time to get a positive result: 24 days
Results
TLA LJ
Positive rate 13% 14%
Negative rate 62% 69%
Contamination rate 24% 17%
Time to positive result
16 days 26 days
Culture results on smear negative samples from Nov 07 to Jul 08
Discussion - Achievements
Almost a third of the TB suspect patients with
negative smear were found positive by culture
More than a half of them had been missed
through clinical algorithm
Culture had allowed the diagnosis of 11% of
the total TB patients
Time for positive results long but improving
Discussion - Challenges
Cost of the laboratory
Contamination rate currently high
Electricity: back-up system required
Keeping the laboratory clean: change shoes,
windows closed, dust coats, etc.
Training of the laboratory technicians is long
BSC maintenance: technician coming from SA
Discussion - Challenges
Expenses for TB culture laboratory (Jan 07-Sept 08)
TOTAL expenses : 280 000 €
17%
30%
25%
28%
Construction Equipment Consumable Staff
48,5 K€
83,6 k€
70 k€
77,8 k€
Conclusions
Routine culture may have an important impact
in the diagnosis of TB in a high HIV prevalence
setting
Is it cost-effective to set up a culture laboratory
in an African rural context? Other alternatives?
TLA has a potential in peripheral settings
compared with others techniques (MGIT, LJ)