V. Borrill, T Schaphoff, G. Shiba, N. Roux and E. Du Toit
Provincial Laboratory For Tissue Immunology, Cape Town, South Africa

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DNA based Group Specific Component (GC) typings using AmpliType DQA1 + PM Amplification and Typing kit are able to identify three different alleles in the GC system, namely GC*A, B and C. Using the isoelectric focusing (IEF) subtyping technique as described by Constans and Viau, five alleles, GC*1S, 1F, 2, AM and AB, as well are variants, are detectable.

Initially, two separate groups of SA Whites, SA Mixed Ancestry Group, and SA Blacks were tested by either the IEF or DNA based techniques. These GC gene frequencies are tabulated below.

IEF = tested performed by the IEF technique DNA = tests performed by the DNA based technique

a = allele gf = gene frequency

Subsequently, 50 random SA Black individuals were tested by both methods. There was absolute correlation between the alleles GC*2 and 1S (detected by the IEF technique) and the corresponding alleles GC*A and C (identified by the DNA based technique). Samples which typed GC*B by the latter method failed to correlate with those which were determined to be GC*1f, AM, AB and Variant using the IEF method.

The AmpliType DQA1 + PM Amplification and Typing Kit is extremely useful in analyzing samples which cannot be typed by other methods. However, it should be noted that when using this kit for parentage testing, results may significantly affect the outcome of a disputed parentage test, particularly in the South African population, where the incidence of GC*AM and AB is high. Conventional GC typing should be used whenever possible.