INDIUM-111 PLATELET SURVIVAL STUDIES ON PLATELET CONCENTRATES (PCVSTORED FOR UP TO 14 DAYS
The effect of extended storage on platelet in vitro and in vivo viability was investigated to determine the reliability and efficacy of Indium-111-oxine radiolabeling of long-term stored platelets. The fitness of various mathematical models for measurement of platelet survival and recovery was also evaluated.33 CPDA-1 PC were prepared and stored for various periods of time (see below) according to standard blood bank methods. The volume of the PC was adjusted to 65-75 mL to prevent pH fall with extended storage. After storage, samples were taken for in vitro assays and for radiolabeling witn Indium-111-oxine using standardized methods. None of the PC had pH<6.3. Afxer reinfusion of the labeled platelets, samples for measurement of radioactivity were taken at three hours and daily for seven days.The uptake {%) of Indium-111 and loss of platelets during the labeling showed no correlation with storage time; the means of the 33 studies were 71±8% and 35±6%, respectively. There was no significant correlation between the parameters and recovery or survival which suggests reliable labeling of nonviable platelets. Excellent fit of the survival data to the multiple hit gamma model was found forpall studies as determined by the coefficient of determination, r 2. The survival curves of platelets stored for one and five days were quite linear as shown by r2 ; with longer storage periods they became more exponential as shown by an increasingly better fit (r2 ) to the log model.Using the gamma model, both in vivo recovery and survival showed a progressive loss with increasing storage duration. This was less evident with the linear model. The loss of in vivo viability paralleled closely a decrease in the in vitro , parameters of platelet quality (discoid shape, hypotonic shock response, ATP content, and oxygen consumption) during storage.In conclusion, this study indicates that extended storage not only yields platelets with reduced recovery, but also platelets with shortened survival.