A blood bank medical technologist wonders about the use of RhIg in children, if it should become necessary to use platelets from an Rh-positive donor for a female Rh-negative child. The inquiring colleague requests input as to what might be the minimum age at which it is recommended to administer RhIg to prevent possible anti-D formation? He wonders if it is advisable to give RhIg to a child as young as 4 months old? He claims to have asked this question of at least one of the RhIg manufactures and was told that it is OK to administer RhIg to children. Please share your policies about the minimum age for using RhIg, and any scientific evidence to support your policy.

The editor advises forum members to review a related discussion posted on this forum in April 2004.

The following responses have been received.

ADDENDA July 26, 2004

1. A transfusion medicine colleague in Buenos Aires reports that his understanding of the literature is that the minimum quantity of red blood cells required to produce primary alloimmunization is 0.03 ml. [Shirley RS et al. in Anderson KC et al. Scientific Basis of Transfusion Medicine. Implications for Clinical Practice. Phil. PA 2000 pp 393-400]. He adds that platelets prepared from whole blood contained 0.42 mL of erythrocytes (Goldfinger and McGinniss (N Engl J Med 1971;284:942) or 0.59 mL (Cid et al, Transfusion 2002; 42: 173-176). In contrast platelets obtained by apheresis contain 0.005 to 0.007 ml of erythocytes (Atoyebi et al., Br J Haematol 2000;111:980) or less (0.00017 ml) with a Gambro-Spectra counter (Molnar et al., Transfusion 2002;42:177). In view of the aforementioned evidence the Buenos Aires colleague would suggest that if an Rh(D) negative patient is transfused with platelets that were collected by apheresis from a Rh (D) positive donor, that there is probably no need to give Rh Immune Globulin (RHIG), whereas if the patient receives platelets prepared from whole blood (buffy or PRP) the patient probably should receive RHIG. According to the Guidelines for the use of platelet transfusion (Br J Haematol 2003;122:1) the Buenos Aires colleague would recomnend a dose of 250 IU of RHIG to cover 5 therapeutic units given in a period of 6 weeks, by a subcutaneous route if the patient is thrombocytopenic.

Editor's note: An IV formulation of RHIG is also available for thrombocytopenic patients.

Please submit comments to the e-Network Forum.

Ira A. Shulman, MD
CBBS e-Network Forum Editor & Moderator