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®â¢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.
Subject(s)
Refrigeration , Specimen Handling/methods , Sputum/microbiology , Tuberculosis/microbiology , Adult , Aged , Child , Child, Preschool , Female , Humans , Indicators and Reagents , Malawi , Male , Middle Aged , Mycobacterium tuberculosis/genetics , Time Factors , Young AdultABSTRACT
OMNIgene·SPUTUM (OM-S) is a sample transport reagent designed to work with all tuberculosis diagnostics while eliminating the need for cold chain. OM-S-treated sputum samples were assayed in several tests after multiday holds. Raw sputa from 100 patients underwent direct smear microscopy, were manually split and assigned to the OM-S group [OM-S added at collection (no other processing required) and tested after 0- to 5-day holds at room temperature] or standard-of-care (SOC) group (NaOH/N-acetyl l-cysteine decontamination, all tested on day of collection). Concentrated smear microscopy, Lowenstein Jensen (LJ) culture, and mycobacteria growth indicator tube (MGIT) culture were performed. For patients with negative direct smear, a second sample was split, with SOC (raw sputum) and OM-S portions (sediment) tested in the Xpert MTB/RIF (Xpert) assay. OM-S group and SOC group results were strongly concordant on all four tests [range, 89% (MGIT)-97% (Xpert)]. OM-S MGIT, LJ, and Xpert tests were in statistical agreement with SOC MGIT as reference. OM-S specimens had lower culture contamination rates (3% vs. 10% LJ; 2% vs. 5% MGIT) but required, on average, 5.6 additional days to become MGIT-positive. The findings suggest that samples held/transported in OM-S are compatible with smear microscopy, LJ or MGIT culture, and Xpert, and perform comparably to fresh sputum samples. Larger feasibility studies are warranted.
Subject(s)
Molecular Diagnostic Techniques/methods , Mycobacterium tuberculosis/isolation & purification , Specimen Handling/methods , Sputum/microbiology , Tuberculosis/diagnosis , Humans , Microscopy , Reproducibility of Results , Sensitivity and Specificity , Time , UgandaABSTRACT
SETTING: German Nepal TB Project, National Tuberculosis Reference Laboratory, Kathmandu, Nepal. OBJECTIVE: To evaluate whether transporting samples in OMNIgene®â¢SPUTUM (OM-S) reagent from a peripheral collection site to a central laboratory in Nepal can improve tuberculosis (TB) detection and increase the sensitivity of Xpert® MTB/RIF testing. DESIGN: One hundred sputum samples were split manually. Each portion was assigned to the OM-S group (OM-S added at collection, airline-couriered without cold chain, no other processing required) or the standard-of-care (SOC) group (samples airline-couriered on ice, sodium hydroxide + N-acetyl-L-cysteine processing required at the laboratory). Smear microscopy and Xpert testing were performed. RESULTS: Transport time was 2-13 days. Overall smear results were comparable (respectively 58% and 56% smear-negative results in the OM-S and SOC groups). The rate of smear-positive, Mycobacterium tuberculosis-positive (MTB+) sample detection was identical for both treatment groups, at 95%. More smear-negative MTB+ samples were detected in the OM-S group (17% vs. 13%, P = 0.0655). CONCLUSION: Sputum samples treated with OM-S can undergo multiday ambient-temperature transport and yield comparable smear and Xpert results to those of SOC samples. Further investigation with larger sample sizes is required to assess whether treating sputum samples with OM-S could increase the sensitivity of Xpert testing in smear-negative samples.
