Evaluating platelet concentrates by platelet indices, thromboelastography, and flow cytometry

Platelet transfusion has been therapeutically used in patients with thrombocytopenia and platelet function defects over the years. The use of advanced techniques may add value in assessing the quality of platelet products. The aim of the study was to assess stored platelet concentrates (PCs) prepared in blood banks for platelet indices, clot strength, and platelet function.

Apart from the routine quality check parameters (platelet count, volume, pH, swirling, and sterility), 24-h-old PCs derived by the platelet-rich plasma method (PRP-PC) were prospectively assessed for various platelet indices using hematology analyzer and clot strength using thromboelastography (TEG). Platelet function (platelet activation and aggregation) was assessed using flow cytometry and compared with freshly prepared PRP.

A total of 43 PRP-PCs that were analyzed had a mean volume of 69.1 ± 5.1 mL, a pH of 6.8 ± 0.3, and a platelet count of 738.8 ± 312.9 × 10³ cells/μL. Swirling was present in all. The platelet distribution width, mean platelet volume, platelet-large cell ratio, plateletcrit, and immature platelet fraction were 9.4 ± 2.7 fL, 8.7 ± 1.2 fL, 16.9% ± 8.9%, 0.6% ± 0.3%, and 4.4% ± 3.9%, respectively. The r-time, k-time, alpha angle, and maximum amplitude were 15 ± 0.3 min, 2.1 ± 0.4 min, 65.2° ± 2.3°, and 76.1 ± 10.1 mm, respectively. Delayed clot initiation and higher clot strength were observed in in 60% (n = 21) and 71.4% (n = 25) of products, respectively Platelet activation of PRP-PC was significantly lower than PRP (0.4 [0.1%-42%] vs. 10.5 [0.8%-32.4%]; P = 0.002). However, platelet aggregation of PRP-PC was significantly higher than PRP (62.0 [26.7%-88.7%] vs. 33.4 [4.9%-55.8%]; P = 0.003).

Platelet indices, TEG, and flow cytometry analysis provides useful information to assess the quality of PCs. However, the variable effects of processing and storage on platelet activity need further exploration.