Blood typing studies in American Indians: Misclassification of R z phenotypes

The detection of exceptional Rh phenotypes (apparently (– –DE–)) among Venezuelan Yanomamo Indians initiated investigation of the reactions of anti‐C (rh′) sera with bloods of the R z phenotypes (CCDEE, CcDEE and CCDEe). It was concluded that since anti‐C reagents may contain differing amounts of two antibodies, anti‐C (rh′) and anti‐Ce (rh i ), the choice of reagent is critical for the detection of R z bloods, such that with an anti‐C serum containing large amounts of anti‐Ce relative to anti‐C, R z R 2 (CcDEE) will be mistyped as R 2 R 2 (ccDEE) and R z r (R 1 R 2 ‐CcDEe) may be mistyped as R 2 r (ccDEe). The error will have its greatest relative effect in populations characterized by substantial R z frequencies and the consequences of such an error (depressed R z gene frequency and elevated R 2 gene frequency) are therefore illustrated from published Indian studies.