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J Infect. 2010 May;60(5):344-50. doi: 10.1016/j.jinf.2010.01.012. Epub 2010 Feb 10.

Comparison of same day versus delayed enumeration of TB-specific T cell responses.

Author information

1
Lung Infection and Immunity Unit, Division of Pulmonology & UCT Lung Institute, University of Cape Town, Department of Medicine, H floor, Old Main Building, Groote Schuur Hospital, Observatory, Cape Town 7925, South Africa.

Abstract

BACKGROUND/OBJECTIVE:

Flexibility in sample processing may improve test utility of the quantitative antigen-specific T cell assay (T-SPOT.TB). We investigated whether delayed sample processing with and without the use of T-Cell Xtend, a proprietary reagent, impacted upon test accuracy.

METHODS:

Blood samples obtained from 363 sequentially recruited tuberculosis suspects or treated patients were processed immediately (day 0) and at different times after receipt of the sample [approximately 24-h (day 1) or approximately 32-h (day 2)] with and without adding T-Cell Xtend.

RESULTS:

T-Cell-Xtend-independent median ELISPOT counts (spot forming cells per million peripheral blood mononuclear cells) were significantly higher at day 1 versus day 0 (114 vs. 100; n=66; p=0.03); inter-time-point agreement between the results was 95.45% and the conversion/reversion rate was 4.55%. By contrast, counts on day 0 without T-Cell Xtend versus day 1 with T-Cell Xtend were similar (56 vs. 56; n=215), inter-time-point agreement between the results was 97.17%, and the conversion/reversion rate was 2.83%. Counts performed at day 2 with T-Cell Xtend were not significantly different from day 0. These findings were independent of HIV status.

CONCLUSION:

There was high agreement between results when samples were processed immediately and after a 24-h delay. However, although the use of T-Cell Xtend appeared to reduce the number of conversions/reversions this reduction was not statistically significant. Larger studies are required to clarify these findings.

PMID:
20152856
DOI:
10.1016/j.jinf.2010.01.012
[Indexed for MEDLINE]

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