Is post-transplant day + 14 immature reticulocyte fraction (IRF) a reliable surrogate marker for predicting early platelet engraftment in pediatric hematopoietic stem cell transplant?

BackgroundProphylactic platelet transfusion is given to patients when the platelet count is less than ten thousand to prevent clinically significant bleeding till platelet engraftment is documented. Despite a very low platelet count, if platelet engraftment is confidently predicted, then platelet transfusion can be avoided in an otherwise stable patient.ObjectiveTo determine the role of post-transplant day + 14 immature reticulocyte fraction (IRF) and immature platelet fraction (IPF) as surrogate markers for early prediction of platelet engraftment in pediatric hematopoietic stem cell transplant patients.Material and methodsThis prospective study was done at the National Institute of Blood Diseases and Bone Marrow Transplantation between January 2017 and December 2020. A total of 56 and 31 patients were enrolled in the deviation and validation cohorts respectively. IPF and IRF were tested on a Sysmex XN-1000 hematology analyzer on days + 14 and + 21 of the bone marrow transplant. Platelet count on day + 14 and the day of engraftment was documented. Spearman correlation analysis and receiver operating characteristic curve (ROC) calculation were done using the statistical package STATA version 12, to determine IRF and IPF cut-off values to predict a median platelet engraftment day.ResultsThe derivation and validation cohorts were statistically comparable. The area under the receiver operating characteristic curve (ROC) for IPF and IRF was 0.53 (95% CI: 0.37 – 0.68, p = 0.750) and 0.74 (95% CI: 0.61 – 0.89, p = 0.001) respectively. A weak inverse correlation (rs0.36, p = 0.007) between IRF and platelet engraftment day was found. The ROC demonstrated that the cut-off value for Day + 14 IRF of 13% has a sensitivity and specificity of 92.9% and 37% respectively. This finding was confirmed in the validation group with sensitivity and specificity of 88.2% and 45.2% respectively.ConclusionThis study found that Day + 14 IRF but not IPF value can reliably predict platelet engraftment by day + 17 post-transplant.