Variability of cytokine concentration in whole blood serum and bronchoalveolar lavage over time.

Measurement of cytokines in peripheral blood and bronchoalveolar lavage fluid (BALF) is a useful method to assess human immune responses in a large range of pulmonary diseases. One of the major pre-analytical challenges of cytokine analysis is the quality and stability of cytokines in the timeframe between sample collection and the separation of supernatant from cells. To evaluate if the method of storage may affect cytokine quantification, whole blood and BALF were collected, aliquoted, and left at room temperature (RT) to be processed at different time points. In addition, sera and BALF were left either at RT or at 4 °C for 24 h after cell separation to test cytokine variations in the absence of cells. Samples were analysed by a multiple array containing ten cytokines. Most of the cytokines analysed (interleukin (IL)-4, IL-5, IL-6, IL-12p70, IL-13, IL-17A, IL-23, interferon (IFN)-γ, and tumour necrosis factor (TNF)-α) did not show significant variations in whole blood and BALF. Levels of IL-8 however, increased after storage of whole blood and BALF for 24 h at RT. Ex vivo IL-8 production seems to correlate with higher numbers of macrophages in collected BALF. These data demonstrate that many cytokines are stable for a brief time after sample collection. For IL-8, freshly collected whole blood and BALF should be quickly processed and frozen to avoid false positive results.