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Title
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Storage of sputum in cetylpyridinium chloride, OMNIgene.SPUTUM, and ethanol is compatible with molecular tuberculosis diagnostic testing
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Author
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Abstract
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| We compared cetylpyridinium chloride (CPC), ethanol (ETOH), and OMNIgene.SPUTUM (OMNI) for 28-day storage of sputum at ambient temperature before molecular tuberculosis diagnostics. Three sputum samples were collected from each of 133 smear-positive tuberculosis (TB) patients (399 sputum samples). Each patient's sputum was stored with either CPC, ETOH, or OMNI for 28 days at ambient temperature, with subsequent rpoB amplification targeting a short fragment (81 bp, GeneXpert MTB/RIF EXpert]) or a long fragment (1,764 bp, in-house nested PCR). For 36 patients, Xpert was also performed at baseline on all 108 fresh sputum samples. After the 28-day storage (D28), Xpert positivity did not significantly differ between storage methods. In contrast, higher positivity for rpoB nested PCR was obtained with OMNI (n = 125, 94%) than with ETOH (n = 114, 85.7%; P = 0.001). Smears with scanty acid-fast bacilli (AFB) had lower rpoB PCR positivity with ETOH storage (n = 10, 41.7%) than with CPC (n = 16, 66.7%; difference, 25%; 95% confidence interval [CI], 3.5 to 46.5; P = 0.031) or OMNI (n = 16, 69.6%; difference, 26.1%; 95% CI, 3.8 to 48.4; P = 0.031), with no difference between CPC and OMNI. Poststorage, the threshold cycle (C-T) values significantly decreased compared to those prestorage with ETOH (difference, -1.1; 95% CI, -1.6 to -0.6; P = 0.0001) but not with CPC (P = 0.915) or OMNI (P = 0.33). For one patient's ETOH- and CPC-stored specimens with a C-T of <10, Xpert gave results of rifampin false resistant at D28, which was resolved by repeating Xpert on a 1/100 diluted specimen. In conclusion, 28-day storage of sputum in OMNI, CPC, or ETOH at ambient temperature does not impact short-fragment PCR (Xpert), including for low smear grades. However, for long-fragment PCR, ETOH yielded a lower PCR positivity for low smear grades, while the performance of OMNI and CPC was excellent for all smear grades. |
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Language
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English
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Source (journal)
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Journal of clinical microbiology. - Washington, D.C.
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Publication
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Washington, D.C.
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2019
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ISSN
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0095-1137
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DOI
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10.1128/JCM.00275-19
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Volume/pages
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57
:7
(2019)
, 9 p.
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Article Reference
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UNSP e00275-19
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ISI
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000472800800006
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Pubmed ID
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31092592
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Medium
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E-only publicatie
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Full text (Publisher's DOI)
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Full text (open access)
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