UV-visible spectrophotometric approach to blood typing II: phenotyping of subtype A2 and weak D and whole blood analysis.

Background: A recently introduced quantitative blood typing approach uses antibody-induced changes in the UV-visible spectra of blood. Changes in the blood spectra's slope, caused by RBC agglutination, are translated into a numerical agglutination index (AI). Comparing the AI value against an established threshold yields a "yes and/or no" output from which to determine the phenotype. The efficacy and flexibility of this approach with whole blood use and the ability to analyze weak D, A2, and A2B were examined.

Study Design And Methods: Two hundred randomly selected blood bank donor samples were coded and forward typed directly from whole blood by using the spectrophotometric analysis. Reverse grouping on plasma from each sample was carried out with a new modified procedure by using higher ratios of plasma to RBCs. Results were compared to typing by an FDA-cleared automated typing system. Twenty-seven weak D samples, 15 A2 and 12 A2B, were similarly analyzed from whole blood. PEG improved detection of weak D, A2 and A2B subtypes.

Results: All two hundred coded samples were accurately typed, yielding identical results to the blood bank analysis in both forward and reverse grouping. All the weak D samples and A2 and A2B samples were clearly identified, having AIs above the type threshold indicator value.

Conclusion: Spectrophotometric blood typing successfully phenotyped ABO and D in 200 whole blood samples. Reverse grouping of plasma was equally successful. The same method can identify weak D and A2 and A2B subtypes.