Abstract
Objective: In the course of research of QuantiFERON®-TB Gold In-Tube (QFT-GIT), we found that re-centrifugation of plasma samples from blood collection tubes decreased IFN-γ values. Thus, we examined the reasons for this phenomenon.
Subjects and methods: Blood samples were taken for QFT-GIT, incubated and centrifuged after incubation to separate plasma and blood cells. Plasma samples were harvested using pipettes and divided into two tubes. One tube was re-centrifuged and the other was not. After re-centrifugation, IFN-γ values of both samples were measured according to manufacturer's instructions.
Results: Most of re-centrifuged samples showed lower IFN-γ values compared with non re-centrifuged samples. We noticed that debris on the surface of separation gel was included in plasma samples after harvest, and when debris was added in ELISA plates, higher IFN-γ values were produced. Microscopic observations showed that debris included many live lymphocytes and these live lymphocytes adhered on plate wells even after intensive washing.
Conclusion: These observations suggested that live lymphocytes adhered on ELISA plate well may produce non-specific reaction, which result in higher IFN-γ values. Therefore, in order to obtain accurate results, QFT-GIT plasma samples after harvesting from QFT-GIT blood collection tubes should be re-centrifuged to spin down live lymphocytes.
- © 2011 ERS
