Polymerase chain reaction determination of RhC, Rhc, and RhE blood types: an evaluation of accuracy and clinical utility.

OBJECTIVE

Polymerase chain reaction amplification of a portion of the RhC/c/E/e gene could lead to a rapid, accurate determination of fetal RhC/c/E status. The purpose of this study was to evaluate the accuracy of this technique by testing for the first time a large number of deoxyribonucleic acid samples derived from individuals whose RhC/c/E status was established by standard serologic methods. We also evaluated the potential clinical utility of polymerase chain reaction to ascertain fetal antigen status.

STUDY

DESIGN

Samples were obtained from Centre d'Etude du Polymorphisme Humain families used for studies of genetic variation (n = 655). Deoxyribonucleic acid was extracted by standard techniques. With few modifications, published primers and reaction conditions were used. Samples were digested with restriction enzymes yielding characteristic electrophoresis patterns for RhC/c/E. Clinical utility was assessed by review of all patients evaluated for erythrocyte sensitization.

RESULTS

RhC-positive (n = 479), RhC-negative (n = 176), Rhc-positive (n = 524), Rhc-negative (n = 131), RhE-positive (n = 131) and RhE-negative (n = 524) samples were evaluated. The sensitivity of RhC/ c and E typing by polymerase chain reaction was 98.3%, 98.1%, and 96.9%, respectively. The specificity of polymerase chain reaction for identifying the RhC/c/E antigens was 91.5%, 94.7%, and 99.2%, respectively.

CONCLUSIONS

Although it would appear that use of polymerase chain reaction to establish RhC/c/E type could aid in evaluation of RhC/c/E sensitization, we are concerned about the instances of antigen-positive individuals characterized as antigen negative. Further study is necessary to determine if this reflects a polymorphism, mutation, a data coding error, or a combination. The Centre d'Etude du Polymorphisme Humain database is known to contain such errors at a rate that may surpass the error rate of our testing. A second molecular technique could be used to achieve better accuracy in the ascertainment of Rh C/c/E type. On the basis of a review of our patient population, molecular deoxyribonucleic acid techniques now available could aid the management of erythrocyte sensitization in pregnancy in > 96% of cases.