A historical perspective on platelet radiolabeling techniques

Abstract

Procedures to evaluate platelet (PLT) recovery and survival have continued to evolve through the years. In the early 1960s, PLT labeling with 51Cr required a large volume of PLTs and labeling in a bag with low efficiency. In 1977, the ICSH recommended standardization of PLT survival determination with 51Cr and labeling the PLT‐rich plasma in a bag; however, issues of poor 51Cr uptake and label manipulation in a large bag still existed. In the mid 1970s, a new radiolabel with 111In was established. Similar recovery and survival results to 51Cr were reported, with the benefits of less blood required and the ability to perform external imaging. A symposium in 1984 detailed recommendations of protocols for radiolabeling of stored PLT concentrates with either 111In or 51Cr and for statistical analysis. Although label preparations did not become standardized, agreement was reached that the best method to determine survival was the gamma nonlinear multiple‐hit model. In 1992, Heaton and Holme showed that concurrent double PLT labels showed a much higher correlation than those separated chronologically and that radiolabel corrections for elution and cell contamination and similar 111In and 51Cr labeling procedures were necessary. The 2004 NIH symposium proposed standardization of the PLT‐labeling method with a control of fresh PLTs compared to the stored PLT product, both from the same donor and with the double‐label 111In‐51Cr method. The procedure included in this supplement represents the evolutionary distillation of numerous approaches and provides a well‐researched, standardized, and dependable means of radiolabeling PLTs.