title: An acute hemolytic transfusion reaction caused by an anti-P1 that reacted at 37 degrees C.
abstract: BACKGROUND
  Hemolytic transfusion reactions (HTRs) due to anti-P1 have rarely been reported. There is only one report (from 1945) of an acute HTR due to anti-P1.
  
  
  METHODS
  A 74-year-old woman with anti-P1 was given blood that had been found to be compatible by the use of prewarmed serum and saline-suspended red cells (RBCs) and of an antiglobulin test with anti-IgG. The test mixtures were not centrifuged or inspected for agglutination after the 37 degrees C incubation phase. After transfusion of 50 mL of P1 + blood, the patient had an acute HTR (hemoglobinemia, hemoglobinuria, and increased blood pressure, temperature, and respiration).
  
  
  RESULTS
  When studied by a reference laboratory, the anti-P1 was shown to be easily detectable (3+ agglutination) by a prewarming technique (saline or low-ionic-strength saline [LISS]), which included centrifugation at 37 degrees C, but only weak reactions were observed when centrifugation after 37 degrees C incubation was omitted. The indirect antiglobulin test was weakly positive (1+) with anti-IgG, but polyspecific anti-human globulin reacted 2+. The anti-P1 agglutinin was IgM, and its titer was 16 at 37 degrees C (prewarmed) and 256 at 23 degrees C; it caused hemolysis of RBCs at 37 degrees C under conditions known to enhance hemolysis. An indirect monocyte monolayer assay gave results of 11.2 and 22 percent in testing of P1 + RBCs incubated with the patient's serum alone and with patient's serum plus fresh normal serum (as a source of complement), respectively (normal < or = 3%).
  
  
  CONCLUSIONS
  An acute HTR was caused by a hemolytic anti-P1 that reacted at 37 degrees C. This antibody was not detected by the hospital in a prewarmed crossmatch that omitted 1) the addition of LISS, 2) the reading for agglutination after the 37 degrees C incubation, and 3) the use of antiglobulin sera containing anti-complement.
authors.affiliation: American Red Cross Blood Services, Southern California Region, Los Angeles, USA.
authors.forename: P A
authors.initials: PA
authors.lastname: Arndt
authors.forename: G
authors.initials: G
authors.lastname: Garratty
authors.forename: R A
authors.initials: RA
authors.lastname: Marfoe
authors.forename: G D
authors.initials: GD
authors.lastname: Zeger
mesh_terms: D000208:Acute Disease; D000368:Aged; D001787:Blood Group Incompatibility / Q000150:complications*; D001788:Blood Grouping and Crossmatching; D005260:Female; D006461:Hemolysis; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D008623:Mercaptoethanol; D009994:Osmolar Concentration; D010127:P Blood-Group System; D013696:Temperature; D017186:Titrimetry; D065227:Transfusion Reaction
chemical_list: D007074:Immunoglobulin G; D007075:Immunoglobulin M; D010127:P Blood-Group System; D008623:Mercaptoethanol