GEDNAP .4. AND .5. THE 4TH AND 5TH STAIN BLIND TRIALS USING DNA TECHNOLOGY

In the collaborative exercise GEDNAP IV one EDTA blood sample (2 ml) a nd 5 bloodstains (0.5 ml on cotton) were investigated and in GEDNAP V, a total of 8 bloodstains (0.5 ml on cotton), including 2 mixed bloods tains. DNA typing was carried out using the RFLP systems YNH24/Hinf I and MS43a/Hinf I and the PCR systems HLA DQ alpha, D1S80, ApoB and YNZ 22. In both exercises approximately 20 laboratories obtained results u sing the RFLP systems. Of the PCR systems, D1S80 was the most commonly used (14 labs in GEDNAP IV; 18 labs in GEDNAP V). The interlaboratory standard deviation for YNH24 in both exercises was approx. 0.6%, for MS43a 0.7-2.2% (GEDNAP IV) and 0.4-1.4%; (GEDNAP V), depending on the fragment size. The fragment size calculation performed in each laborat ory yielded a standard deviation twice that obtained when the fragment size calculation was performed centrally (IfR, Munster). In GEDNAP II I, a system-specific corridor was developed to define the limits of de viation; this was modified for the present study by combining the frag ment size ranges of YNH24 and MS43a. In both studies a subgroup of lab oratories was involved in preliminary exercises using three PCR VNTRs and the system KLA DQ alpha. Owing to the substantial variation in exp erience of the participating laboratories with PCR typing the results obtained in these two studies do not fulfil the basic quality criteria of the GEDNAP studies.