Recruitment of platelets, white blood cells, and hematopoietic progenitor cells during high-yield plateletpheresis.

Background: Previous observations suggested recruitment of platelets (PLTs) and white blood cells (WBCs) during plateletpheresis and recruitment of hematopoietic progenitor cells (HPCs) by HPC apheresis. Quantification of recruitment helps to optimize yields and safety of these procedures; detection of WBC or HPC recruitment during plateletpheresis may further elucidate the mechanisms.

Study Design And Methods: This study was a prospective cohort study with 68 single-needle plateletpheresis donations (23 double, PLT yield ≥4.8 × 10(11) ; 23 triple, ≥7.2 × 10(11) ; 22 quadruple, ≥9.6 × 10(11) ). We measured PLTs, WBCs, WBC subpopulations, and circulating HPCs (CD34 mRNA) before, during, and after apheresis; calculated PLT recruitment and ratio of recruited to yielded PLT; and propose a novel concept to optimize the prediction of the PLT counts after apheresis (PLT(post) ).

Results: PLT recruitment (mean ± SD, 1.56 ± 0.31) caused a higher PLT(post) than predicted by the instrument (164 × 10(9) ± 23 × 10(9) vs. 111 × 10(9) ± 31 × 10(9) /L; p < 0.0001) in all three groups. The ratio of recruited to yielded PLT was 0.36 ± 0.15. The WBC count decreased by 9% to the time before rinse-back and returned to the baseline thereafter. No changes in circulating HPCs occurred.

Conclusions: PLT recruitment during high-yield plateletpheresis facilitates the harvest of multiple PLT units in a single donation. The use of the ratio of recruited to yielded PLT may optimize the algorithm to predict PLT(post) . There was no recruitment of WBCs and HPCs during plateletpheresis. Therefore, the previously observed recruitment of HPCs during HPC apheresis seems to be related to other factors than the apheresis procedure itself.