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Samples from trios were independently tested in two laboratories to compare the rates of exclusion and the cumulative paternity index (CPI) obtained by each battery of tests.

Samples were collected through the Parentage Testing Department of the Memorial Blood Centers of Minnesota. All samples were tested for markers in the following systems: ABO, RH, MNSs, Kell, FY, JK, and a minimum of two RFLPs (D12S11, and D17S79 restricted with Pst I). Whole blood was spotted on filter paper cards and sent to the Medical College of Virginia where the following four STR loci were amplified and analyzed: VWA31/A, TH01, F13A01, and FESEP.

Tested men excluded in two or more systems by the RBC/RFLP test battery were also excluded by one or more of the STR loci. No men were excluded by either battery alone. In 45% of the exclusion cases, only one of the four STR loci provided evidence of non-paternity. Since AABB Parentage Testing Standards require exclusion by more than one STR or other DNA locus, these cases would require testing of additional loci. In 26% of the non-excluded cases tested by RBC/RFLP additional RFLP systems (D7S467 and/or D4S163) were required to achieve a CPI greater than 100. In comparison, additional tests would have been required to obtain a greater than 100 in 14% of the non-excluded trios tested by the STR battery.

Both batteries of tests give similar results in cases of disputed parentage. No trios tested by the RBC/RFLP battery needed additional testing to prove non-paternity. Testing only with the STR battery resulted in a higher percentage of cases with a CPI greater than 100.