False-positive pregnancy test after passive transfusion of beta-human chorionic gonadotropin from donor red blood cells during erythrocytapheresis.
BACKGROUND
Patients transfused with blood products may passively receive soluble antibodies, proteins, and other analytes that persist during the collection, processing, and transfusion of the blood product. In this report, a female patient who received transfusion of five red blood cell (RBC) units during erythrocytapheresis later demonstrated an unexpected positive result in assays for the beta-subunit of human chorionic gonadotropin (bHCG), a screening test for pregnancy. The result caused postponement of an elective surgical procedure. A follow-up test 1 week later was negative.


METHODS
To investigate the possibility of passive transfusion of the hormone from a donor RBC unit, a sample from each of the units transfused was assayed for the level of bHCG.


RESULTS
One of the 5 units transfused to the patient had a high level of bHCG. The observed bHCG level in the recipient was found to be comparable to the predicted level, given the donor's plasma bHCG level and accounting for the dilution factors in the preparation of the RBC unit and the erythrocytapheresis procedure and the in vivo t((1/2)) of the hormone.


CONCLUSIONS
The donor, who was unaware of her pregnancy status at the time of donation, harbored a high bHCG level that caused the positive test result in the recipient patient's serum and urine. If an unexpected analyte or serology is detected in a recipient of a blood transfusion, it is important to consider the possibility of passive transfusion of the analyte.
Shelat
Suresh G
SG
Apheresis and Transfusion Medicine, Hematology Laboratory, Children's Hospital of Philadelphia, Abramson Research Center, Philadelphia, Pennsylvania 19104, USA. Shelat@mail.med.upenn.edu
Friedman
David F
DF
Meny
Geralyn M
GM
Smith-Whitley
Kim
K
Carlow
Dean
D
Norris
Robin
R
D000293:Adolescent; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000032:analysis* / Q000652:urine; D017707:Erythrocyte Transfusion; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D011247:Pregnancy; D011258:Pregnancy Tests / Q000592:standards
D018997:Chorionic Gonadotropin, beta Subunit, Human