Comparative study of OMNIgene®•SPUTUM reagent versus cold-chain for the transportation of sputum samples to GeneXpert®MTB/RIF testing sites in Malawi

Abstract

Abstract Background The study was conducted in a remote sputum sample collection sites and GeneXpert® MTB/RIF testing centers to detect Mycobacterium tuberculosis in Malawi. The main purpose of the study was to evaluate whether sputum samples stored and transported with OMNIgene®•SPUTUM (OM-S) medium perform comparably to the routine cold-chain stored and transported samples for GeneXpert testing to detect Mycobacterium tuberculosis. Methods Two sputum samples from each of 362 tuberculosis suspects were randomly assigned to the OMNIgene treated (OM-S group) or the standard-of-care group (SOC; transported via cold chain). All specimens were tested at regional GeneXpert testing sites using the expectorated (raw) sputum protocol. Demographic, clinical, transport/storage and Xpert data were recorded for each specimen pair. Agreement between the SOC and OM-S groups’ Xpert results was evaluated using Cohen’s kappa analysis. Results Mean patient age was 42.3 years (range 2–79 years), 77% of patients were female, and 80% were HIV-positive. Mean transport/storage time was 6.7 days (range, 0–29 days). The rates of MTB positivity for the OM-S and SOC groups were comparable (11.8 and 11.2%, respectively), inter-test agreement was “very good” (κ = 0.97), and overall percent agreement was 99%. Two specimen pairs (both mucoid, one 13 days transport, one 1 day transport) had discordant Xpert results. Conclusion OM-S-treated sputum specimens can undergo multi-day ambient-temperature storage as well as transport and yield Xpert results comparable to those of cold-chain-transported samples in Malawi.

Keywords

• OMNIgene
• Sputum
• GeneXpert
• Mycobacterium tuberculosis
• Preservation
• Specimen transport medium