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)