Influence of separator gel in blood sampling tubes for perfluoroalkyl and polyfluoroalkyl substances analysis

For several years, concerns about perfluoroalkyl and polyfluoroalkyl substances (PFAS) have been growing, and clinical laboratories may have to perform a growing number of PFAS analyses. The use of serum tubes without a separator gel is currently recommended for the quantification of PFAS due to the concern that the compounds may adsorb to the gel. The impact of gel adsorption on the accuracy of the results, however, has not been evaluated.

Aliquots from a pool of blood spiked with PFAS were stored in gel-free clot activator tubes (CATs) and gel-containing BD SST II Advance tubes (serum separator tubes) for 2, 8, and 24 hours. The CATs and serum separator tubes were collected from 15 volunteers under typical sampling conditions. Concentrations of 16 PFAS were analyzed using liquid chromatography-tandem mass spectrometry, and the percentage of change in PFAS levels between both tube types was computed.

Results showed minimal changes (<5%) for most PFAS within 24 hours, except for long-chain perfluorosulfonates (including perfluorooctane sulfonate), which seemed to exhibit adsorption of the gel. In samples from volunteers, the observed changes were statistically significant for perfluorooctane sulfonate (P <.001).

Based on our analysis, we recommend using CATs to avoid PFAS underestimation.