Feasibility and cost analysis of programmatic implementation of Microscopic-Observation Drug Susceptibility (MODS) assay in Nigeria

Abstract

Objectives: Detection of Multi-drug resistant tuberculosis in Nigeria still remains a challenge. We evaluated the feasibility of programmatic implementation of the Microscopic-Observation Drug Susceptibility (MODS) assay, a rapid culture and drug susceptibility testing technique for drug susceptibility testing in a low resource setting.

Method: In a novel laboratory setting in Nigeria, we obtained data from the market on the cost of materials necessary for MODS assay. Three routinely collected sputum specimens from 160 tuberculosis suspects were evaluated by smear microscopy while only the early morning specimen was used for MODS culture.

Results: MODS assay detected M. tuberculosis in 97.7% (42/43) of smear positive and 6.0% (7/117) of smear negative TB suspects. There was a statistically significant advantage of a single MODS culture over 3 smear microscopies (P=0.019). The modal time from culture of specimen to detection of M. tuberculosis and availability of drug susceptibility result for MODS was 7days with a mean of 8.4 days (Range= 5-13 days). Culture and susceptibility result was available in 18.4% (9/49) of patients within 5days of culture. Turnaround time for smear microscopy in the centers was 3 days. Cost of processing one specimen by MODS assay in the study was USD2.65. Multi-Drug resistant tuberculosis (MDR-TB) was detected in 4.1% (2/49) while Isoniazid mono-resistance was detected in 2.0% (1/49) of the culture positive cases. All the drug resistant isolates were from re-treatment cases with a statistically significant association (P=0.005).

Conclusion: The MODS technique is simple, and its implementation in this novel setting was feasible. MODS can be scaled up to meet the demand for MDR-TB confirmation in XpertMTB/Rif deployed sites in Nigeria.

Keywords: Tuberculosis, MDR-TB, Mycobacterium tuberculosis