OBJECTIVETo determine if there are any differences in the number of exclusions from paternity of men using an anonymous parentage testing service compared with that of men using an in-person parentage testing service provided by the same company in Hong Kong SAR of China.

METHODSComparable numbers of consecutive anonymous and in-person parentage tests conducted by the same company were analyzed.

RESULTSMen using an anonymous parentage testing service were excluded from paternity at a significantly greater rate (P < 0.001), compared with men using an in-person parentage test service.

CONCLUSIONSThe results obtained from anonymous parentage testing indicate that the number of families containing children of doubtful parentage is much greater than expected previously. As illegitimate children are known to suffer greater degrees of abuse and neglect, this finding poses serious social questions regarding the welfare of families, which the relevant authorities should acknowledge and address.