To the Editor.—
In "Therapeutic Effect of Vitamin C: A Co-Twin Study" (237:248, 1977), zygosity was determined by dermatoglyphic analysis and extensive blood typing. We do not criticize, but intend to point out that postnatal diagnosis of zygosity is one of the most difficult tasks when data of placental examination at birth are not available. Diagnosis cannot be accurate unless at least physical characteristics of the twin pairs are also studied.Dermatoglyphics are of limited use in the diagnosis of zygosity. Prints of monozygotic twins may have similar patterns, but they are not identical and may be quite dissimilar.1 Although some studies2-4 have indicated certain differences in the handprints and footprints of monozygotic and dizygotic twins, there are no definite dermatoglyphic parameters for diagnosis of zygosity. In one study,2 diagnosis of zygosity based on fingerprints alone had an average error of 22.6%, but when supplemented with information
Rao VS, Greene CA, Prasarn V. Diagnosis of Twin-Zygosity by Dermatoglyphics. JAMA. 1977;237(25):2718. doi:10.1001/jama.1977.03270520028004
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