N. Sparks, Z. Ryklief, L. Halliday and E.D. du Toit
Provincial Laboratory for Tissue Immunology, Cape Town, South Africa

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The popular South African media give the impression that DNA tests will solve any problems in cases of disputed paternity. The sentence "DNA tests show that he is the father" may often be seen in articles of this nature.

DNA test results on their own, in rare cases, may give an unexpected result. 1 out of 550 routine cases tested over a 12 month period required extensive investigation.

A case of disputed paternity was referred to our department. The clients were bled in an outlying district and the specimens were received via the postal service.

Routine tests show one first order exclusion, on the ABO blood group system. The mother was typed as a blood group O, the child as a blood group B and the putative father as blood group A. Our policy is to exclude on 2 separate systems. We therefore followed with VNTR single locus probe DNA testing, expecting DNA to confirm our findings. However, the following five probes showed no exclusion: 3' alpha, YNH24, CMM101, TBQ7 and EFD52.

Initially, we considered the possibility of incorrect specimen identification. The clients were re-bled and the original results confirmed.

Family studies were undertaken. Testing on the mother’s family proved uninformative. We have identified a blood group B in the father of the putative father. Further family studies are in progress.

If only DNA testing had been done, it would have been assumed that the paternity of the alleged father had been confirmed.