Page 243 - Personalised medicine of fluoropyrimidines using DPYD pharmacogenetics Carin Lunenburg

CYP2D6 and gene duplication. The Luminex and INFINITI assays include 15 SNPs and gene duplications. At Eramsus MC Taqman or PCR-RFLP were used to determine 15 and 25 variants from the Luminex/INFINITI assays and AmpliChip assay respectively. CYP2D6 and CYP2C19 are involved in different drug metabolisms.5 The other routinely tested SNPs are SNPs in genes coding for enzymes involved in drug metabolism from the cytochrome P450 (CYP2C19*17, CYP2C19*2, CYP2C19*3, CYP2C9*2, CYP2C9*3, CYP3A4*22, CYP3A5*3, CYP3A5*6), SNPs correlated to fluoropyrimidine-induced toxicity (DPYD*2A, DPYD*13, c.2846A>T, c.1236G>A),6 simvastatin-induced toxicity (SLCO1B1 rs4149056),7 calcineurin inhibitors pharmacokinetics (ABCB1-c1236t, ABCB1-g2677t, ABCB1-t129c, ABCB1-t3435c),8 warfarin-induced toxicity (VKORC1 rs9934438)9 and thiopurines-induced toxicity (TPMT*2, TPMT*3A/*3B/*3C).10 All results of which a second independent genotyping test was executed were reviewed. For Erasmus MC CYP2D6 genotypes were taken into account. Mismatches between two tests were directly investigated upon discovery and summarized in this study.
Supplementary Results
Current confirmation practice
The 460 laboratories participating in the proficiency testing program organized by RfB received the hard-copy questionnaire focusing on DPYD. In addition, the questionnaire was 9 also sent by e-mail to 16 Dutch laboratories participating in the proficiency testing program
of SKML. In total, we received 35 completed questionnaires, of which six laboratories do not execute genotyping assays. Of 63 of the 460 European laboratories it is known that they test
for DPYD and these laboratories were more likely to reply to our questionnaire compared to laboratories not testing for DPYD. Response rate in European laboratories testing for DPYD
was 27% (17 out of 63) compared to 75% response (twelve out of 16) in Dutch laboratories testing for DPYD. One laboratory responded to both Dutch and European questionnaires,
and was only taken into account once. Supplemental Figure 1 shows the flowchart of invited laboratories and their responses.
The first question was asked to determine which DPYD SNPs are currently tested in different laboratories. 16 out of 22, and eleven out of twelve responders in Europe and the Netherlands execute DPYD genotyping, respectively. Of all centres genotyping for DPYD, only one centre did not test for the most-described DPYD variant in literature: DPYD*2A. Five centres genotyped only one variant (DPYD*2A), whereas the other centres combined multiple SNPs in their genotyping program. The four variants for which dosing guidelines are available, were most frequently tested. The different genotyped DPYD variants against the total number of responders are shown in Supplemental Figure 2.
The second question aimed at gaining insight into which techniques were used for genotyping. Only answers of laboratories testing for DPYD (N=27) were included in the evaluation of questions 2 and 3. Multiple answers could be given to questions 2 and 3. Of all laboratory techniques, the TaqMan assay and melting curve analyses were most frequently used. There were no considerable frequency differences of the applied techniques between Europe and the Netherlands. An overview of all applied genotyping techniques is shown in Supplemental Figure 3.
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