title: A gel technology system to determine postpartum RhIG dosage.
abstract: Failures of Rh immune globulin (RhIG) prophylaxis occur when the dose is too small. We report a test using a gel technology (GT) method to replace the Kleihauer-Betke (K-B) test to assess fetomaternal hemorrhage (FMH) and assist in determining the minimum necessary dose of RhIG. Cord blood (O, D+) was mixed with adult blood (O D-) to mimic an FMH of 10 mL, 20 mL, 28 mL, and 40 mL. Test samples were incubated with anti-D at known concentrations and centrifuged. The supernatant was titrated against D+ and D- red cells using GT and an interpretation of the required RhIG dose was made. Results were compared with the K-B test. Results were easily discernible and interpretations leading to determination of recommended RhIG dosage were reproducible. Correlation to standard K-B testing was confirmed. Elapsed time for result availability by GT testing was 60 minutes, with a direct technical time requirement of 30 minutes. The GT system is easier, objective, and quantitative, and compares well to the standard K-B test. A single procedure will allow assessment of the extent of FMH in the great majority of cases. This technique works well in determining the appropriate dose of anti-D required to treat D- patients with D+ newborns. There are potential cost savings in decreased use of RhIG, less direct technical time required, and more rapid availability of results.
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Canada.
authors.forename: J R
authors.initials: JR
authors.lastname: Fernandes
authors.forename: R
authors.initials: R
authors.lastname: Chan
authors.forename: A S
authors.initials: AS
authors.lastname: Coovadia
authors.forename: M D
authors.initials: MD
authors.lastname: Reis
authors.forename: P H
authors.initials: PH
authors.lastname: Pinkerton