76 Preparation for Intrauterine Transfusion: Comparison of Hemoglobin and Hematocrit Measurements Using Spun Hematocrit, Point-of-Care Hemoglobin Analyzer, and Automated Cell Counter

Severe fetal anemia may be treated with intrauterine transfusion (IUT) of red blood cell units (RBCs). Our hospital’s recent practice has been to volume-reduce a RBC that is fresh (<7 days old), leukoreduced (CMV-safe), hemoglobin S negative, and crossmatch-compatible with maternal plasma. Prior to issue, a sample of the volume-reduced RBC would be sent for hematocrit (HCT) measurement on a Sysmex XN-9000 automated hematology analyzer. After ensuring the RBC meets the requested 70% HCT (±5%) and gamma-irradiation, the volume-reduced RBC would be sent to obstetrics (OB) for IUT. The OB team at our hospital will not use an RBC with a spun HCT greater than 75% for IUT due to concern for high viscosity and possibility of catastrophic umbilical vein thrombosis. The OB team currently performs a bedside spun HCT on the volume-reduced RBC and an umbilical venous blood sample. This study examines the correlation between HCT and hemoglobin measurements using spun HCT, automated cell counter Sysmex XN-9000, and point-of-care hemoglobin analyzer Hemocue 201. For five AS-3 RBCs, three volume-reduced RBCs, and 10 cord blood samples, measurements were made on the three platforms of interest. Hemoglobin measurements on the Hemocue and XN-9000 correlated well for all three sample types (y = 0.94x + 0.84 where y = Hemocue hemoglobin and x = XN hemoglobin, r2 = .996 with hemoglobin 12.5–26.7 g/dL). The HCT measurements using spun HCT and XN-9000 also correlated well for all three sample types (y = 1.08x – 4.06 where y = spun HCT and x = XN HCT, r2 = .96 with HCT 42.5–78.5%), but more variability was seen with cord blood samples compared to RBCs (spun HCT and XN HCT difference ranged from –6.4% to +5.8% in cord blood samples vs –0.9 %to +3.3% in RBCs). The XN-9000 HCT/hemoglobin ratio averaged 3.1 (SD = 0.20, maximum 3.4, minimum 2.8). Multiplying the Hemocue hemoglobin by 3.1 yields a calculated HCT that is between –5.3% and 6.2% different from the XN-9000 HCT and with good correlation (y = 0.97x + 1.29 where y = calculated HCT and x = XN HCT, r2 = .93). With this study, our laboratory medicine department has been in discussion with our OB colleagues about using the Hemocue hemoglobin measurement to confirm the need for IUT and calculate the volume of IUT dose based on point-of-care Hemocue hemoglobin measurements rather than bedside spun HCTs performed by the OB team. At the same time, we will be correlating the OB bedside spun HCT performed by OB fellows with the spun HCT performed by medical laboratory scientists in the hematology lab. Finally, we have also determined that unmodified RBCs (n = 5, HCT range 62.9–72.7%, mean 68.5%) can meet the desired HCT requested for IUT. A future study may explore outcomes of IUT with RBCs suspended in AS-3/CP2D/plasma compared to volume-reduced RBCs.