Policies and procedures related to weak D phenotype testing and Rh immune globulin administration. Results from supplementary questions to the Comprehensive Transfusion Medicine Survey of the College of American Pathologists.

OBJECTIVE: To determine and evaluate policies and procedures related to weak D phenotype testing and terminology and the administration of Rh immune globulin in selected clinical situations. Design, Setting, and Participants.-Institutions participating in the College of American Pathologists 1999 J-A Comprehensive Transfusion Medicine Survey program were asked to respond to a series of supplementary questions related to weak D phenotype testing and Rh immune globulin administration. More than 3500 institutions and transfusion services participated.

RESULTS: Most supplementary questions elicited more than 3000 responses. Despite no clinical or regulatory mandate, 58. 2% of transfusion services routinely perform an antiglobulin test for the weak D phenotype in patients who test negative with anti-D reagents. Significant differences were found concerning the transfusion of blood components to patients with the weak D phenotype and the administration of Rh immune globulin to these individuals. At least one patient with the weak D phenotype with anti-D alloantibody formation was observed during a 12-month period by 31.8% of transfusion services.

CONCLUSIONS: Significant variability concerning policies and procedures related to weak D typing and terminology was found in this survey. Transfusion of blood components to patients with the weak D phenotype and the administration of Rh immune globulin also demonstrated variations. Anti-D alloantibody formation by patients with the weak D phenotype may not be as rare as previously thought. Additional study related to the clinical significance of these results is warranted.