PREVALENCE AND SPECIFICITY OF BLOOD GROUP ANTIBODIES IN SWISS BLOOD DONORS


Edi Matheis, Annelies Böhlen-Bodmer, Karin Hardegger, Annette Schille and Beat M. Frey Stiftung Zürcher Blutspendedienst SRK, CH-8001 Zürich (www.zhbsd.ch)

BACKGROUND:
 Swiss Red Cross descriptions require exclusion of blood donors (BD) carrying red blood cell antibodies (AB) from blood donation. Until 1999, screening for antibodies (AST) was requested after transfusion (tx) or pregnancy (py). Since 2000 every blood donor is screened by AST. The significance of this precautionary measurement might depend on AB specificity, its titer, the blood product (BP) transfused and on receipient factors. Retrospectively, we analysed prevalence and specificity of ever discovered ABs in BDs of our blood transfusion service.

METHODS: 
Files of 306 BDs with confirmed positive ASTs were identified in our donor registry. ASTs were performed by hemagglutination assay in mikrotiter plates using a mixture of two test cells with the following antigen spectrum (D, C, E, c, e, Cw, K, k, Kpb, Fya, Fyb, Lub, Jka, Jkb, M, N, S, s, Lea, Leb, P1, Xga, Coa). Sera with confirmed positive AST were scrutinized by differentiating and titering of antibody(ies) using gel-sedimentation techniques.

RESULTS:
306/56148 (0.55%) of performed ASTs were found positive. 297(97%) positively tested BDs had Allo-AB (alAB) and 9(3%) had Auto-AB (auAB). The female/male ratio of AB carriers was 222(73%)/84(27%). Mainly donors older than 30 years had ABs. Among younger donors (<30 years), equal sex distribution of AB carriers was found, BDs >30 years carrying ABs were mainly women (60%-75%) per age decade. 230(77%) of AB carriers had history of homologous tx or py (induced alAB) and 67(23%) had no sinsibilisation risks (naturally occurring alAB). The specificity of induced alABs were Rhesus>Kell>Duffy>Kidd>Lutheran and of naturally occurring alABs MNS>Lewis>Rhesus, resp. Natural Rh alABs were exclusively low titer anit-E, while induced Rh alABs showed the whole spectrum of Rh specificity, but mainly anti-D. Titer of ABs and other biological characteristics will be presented.

CONCLUSIONS:

  • Mainly female BDs are carrier of alAB, preferentially after the age of 30 years.
  • Increasing frequency of male BDs carrying alAB by age reflects the increasing tx exposure with consecutive sensibilisation risk of these donors.
  • The most prevalent alABs in BDs have Rh-, Kell- or Duffy specificity and therefore may harbour significant risk to potential receipient of the respective BPs.
  • Since some alABs show dose effect (eg. anti-c, anti-M), composition and antigen densities of search cells largely determine test sensitivity of AST.