title: Antibodies to co-trimoxazole (trimethoprim and/or sulfamethoxazole) related to the presence of the drug in a commercial low-ionic-strength solution.
abstract: BACKGROUND
  Drug-dependent antibodies have been associated with approximately 10% of acquired immune hemolytic anemia cases. These antibodies are a rare cause of interference in pretransfusion red blood cell (RBC) serologic testing. The aim of this work was to report three cases of subjects developing antibodies against co-trimoxazole, a combination of trimethoprim (TMP) and sulfamethoxazole (SMX).
  
  
  METHODS
  Blood samples of donor/patients were referred to our laboratory for the exploration of a positive antibody detection test. There was no recent history of drug taking. Antibody identification was performed by gel test using an indirect antiglobulin test, with reagent RBCs in low-ionic-strength solutions (LISS) containing co-trimoxazole or not.
  
  
  RESULTS
  All three sera showed positive reactions when RBCs were resuspended in LISS containing co-trimoxazole, but negative reactions when RBCs were resuspended in LISS without antibiotic. We detected antibodies against co-trimoxazole showing three different antibody patterns: anti-TMP plus anti-SMX, anti-TMP alone, or anti-SMX alone. Anti-TMP showed an apparent anti-Ku specificity in the two cases where it was present. Anti-SMX showed an apparent anti-H specificity in one of the two cases described. The drug-dependent antibodies were not associated with acquired hemolytic anemia or other pathologies.
  
  
  CONCLUSIONS
  Antibodies against co-trimoxazole may only be detected when using a diluent for reagent RBCs containing the drug in question. Antibody pattern (anti-TMP and/or anti-SMX) may vary according to individuals' immune response. Drug-dependent antibodies may react as antibodies against a high-prevalence antigen, supporting the hypothesis of antibodies to drug and membrane components. Drug-dependent antibodies such as anti-co-trimoxazole may be a serologic finding without clinical features.
authors.affiliation: Institut National de la Transfusion Sanguine, CNRGS-INSERM U665, Paris, France. bnpham@ints.fr
authors.forename: Bach-Nga
authors.initials: BN
authors.lastname: Pham
authors.forename: Dominique
authors.initials: D
authors.lastname: Gien
authors.forename: Farid
authors.initials: F
authors.lastname: Bensaad
authors.forename: Jérome
authors.initials: J
authors.lastname: Babinet
authors.forename: Isabelle
authors.initials: I
authors.lastname: Dubeaux
authors.forename: Philippe
authors.initials: P
authors.lastname: Rouger
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Le Pennec
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000890:Anti-Infective Agents / Q000276:immunology*; D000906:Antibodies / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D012996:Solutions; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000276:immunology*
chemical_list: D000890:Anti-Infective Agents; D000906:Antibodies; D012996:Solutions; D015662:Trimethoprim, Sulfamethoxazole Drug Combination