Effective immediately, the Kleihauer-Betke (acid elution) test for detection of erythrocytes containing fetal hemoglobin utilized for detection and quantitation of feto-maternal hemorrhage will be replaced by a flow cytometric assay employing anti-hemoglobulin F antibody as the detection reagent. The new test will be performed in the Immunopathology laboratory (5238 RCP) and orders for the K-B test sent to the Hematology Laboratory will be redirected to Immunopathology.

The flow cytometric assay has significantly greater sensitivity than the K-B test and is not dependent upon observer microscopic interpretation. It readily distinguishes fetal erythrocytes from adult erythrocytes with increased concentrations of hemoglobulin F (so-called "F cells") which are present in patients with hemoglobinopathies, thalassemia and hereditary persistence of hemoglobin F, so that even in women having these conditions, feto-maternal hemorrhage can be accurately quantitated.

Specimen required: 1 small lavender-top tube of maternal blood.

Requisition: A new 0-8 Immunopathology Request form listing the new test under "Flow Cytometry" is in press. Until it is available, please write "Flow Rh Cytometry for HbF" on either the 0-4 (Miscellaneous requisition) or the current 0-8 Immunopathology requisition.

Reference range: Less than 0.45%.
Note: This reference range is established as the level at which greater than the usual 300 micrograms dose of Rh immunoglobulin administered to Rh-negative women at delivery is required to prevent sensitization. The "normal HbF value" for non-pregnant adults is less than 0.1%.

Turn-Around Time: 24 hours, Monday-Friday. Specimens received on Saturday or Sunday will be tested on Monday. Special processing will be authorized if a time delay of >72 hours from delivery until a routine workday will occur due to a holiday. Please contact the Clinical Pathology resident on-call (131-3404) to make arrangements.

Questions or comments may be directed to:
James A. Goeken, M.D. (6-1966, <james-goeken@uiowa.edu>)
Director, Immunopathology Laboratory

(or)

Lisa A. Horning, MT, SI (ASCP) (6-2846, <lisa-horning@uiowa.edu>)
Lead Scientist, Immunopathology Laboratory