BLOOD COMPONENTS Value of calcium and phosphate in a bicarbonate-containing platelet additive solution with low plasma levels in maintaining key in vitro platelet storage parameters Andrey Skripchenko, Annette Turgeon, Dedeene Thompson-Montgomery, Helen Awatefe, and Stephen J. Wagner BACKGROUND: Use of recently developed platelet (PLT) additive solutions (PAS) with 5% plasma levels may reduce the frequency and/or severity of transfusion reactions attributed to plasma. PLTs suspended in bicarbonate-containing PAS-5 with 5% plasma levels can maintain key PLT parameters during 7-day storage. This study evaluates the role of calcium and phosphate, as constituents of PAS-5, in maintaining PLT parameters. STUDY DESIGN AND METHODS: An Amicus apheresis PLTunit (n 5 13) was equally divided into four 60-mL aliquots in CF-250 polyolefin bags. Four different formulations of PAS-5 were prepared: PAS-5, PAS-5 without phosphate (2PO 4 ), PAS-5 without calcium (2Ca), and PAS-5 without Ca and phosphate (2Ca/ 2PO 4 ). PLTs were centrifuged, and the supernatant was expressed and replaced with the respective PAS, yielding PLTs suspended in 95% PAS and 5% plasma. PLTswere stored at 20 to 24  C with agitation for 7 days. PLT in vitro parameters were evaluated on Days 1, 5, and 7. RESULTS: In PLT PAS-5 aliquots, pH levelswere maintained better compared with those in 2Ca and –Ca/ 2PO 4 aliquots. Glycolysis was greater in 2Ca and –Ca/ 2PO 4 PLTaliquots compared with PAS-5 aliquots. Hypotonic stress response and morphology were less and p-selectin (CD62P) binding was greater in –Ca/ 2PO 4 PLTaliquots. The accumulation of reactive oxygen species was greater in –Ca/2PO 4 PLTs. Phosphorylation of p38 mitogen-activated protein kinase (MAPK) was greater in –Ca and 2Ca/2PO 4 PLTaliquots during storage. CONCLUSION: The removal of calcium and phosphate from PAS-5 leads to the activation of p38 MAPK and deterioration of key PLT storage parameters. H istorically, platelets (PLTs) have been collected and stored in 100% plasma using PLT-rich plasma (PRP), buffy coat (BC), and apheresis methods. The development of PLT-additive solutions (PAS) to replace some of the plasma with bal- anced salt solutions and, in some cases, glucose, has the potential to improve storage, reduce the frequency and/or severity of plasma-associated transfusion reactions, reduce the volume of incompatible plasma, and enable the collection of more concurrent plasma during aphere- sis. 1-11 The development of different formulations of PAS may allow for improved storage of PLTs undergoing path- ogen reduction. 12 In a more recently developed PAS, M-Sol, calcium was identified as important for the maintenance of key in vitro storage properties. 13 The absence or presence of cal- cium in PLTs suspended in 95% M-Sol containing 5% plasma affected the expression of P-selectin, PLT activation-dependent granule membrane protein (cluster of differentiation 62P [CD62P]); the extent of shape change (ESC); and the hypotonic stress response (HSR). In addition, calcium is extremely important in signal ABBREVIATIONS: CM-H 2 DCFDA 5 5-[and-6]-chloromethyl- 2 0 ,7 0 -dichlorodihydrofluorescein diacetate, acetyl ester; ESC 5 extent of shape change; HSR 5 hypotonic stress response; MAPK 5 mitogen-activated protein kinase; PAS 5 platelet additive solution(s). From the American Red Cross Biomedical Services, Holland Laboratory, Rockville, Maryland. Address reprint requests to: Stephen J. Wagner, American Red Cross, 15601 Crabbs Branch Way, Rockville, MD 20855; e- mail: stephen.wagner@redcross.org. Received for publication August 2, 2016; revision received September 12, 2016; and accepted September 13, 2016. doi:10.1111/trf.13894 V C 2016 AABB TRANSFUSION 2017;57;349–356 Volume 57, February 2017 TRANSFUSION 349