Interference in measurement of potassium caused by bacterial contamination of an analyzer.

with the replacement of A1298C wild-type reverse primer with A1298C mutant reverse primer, which had the following sequence: 5 -GGTAAAGAACAAAGACTTCAAAGACACTGTG-3 (Sigma-Aldrich). ARMS PCR conditions were 95 °C for 5 min; 40 cycles of 95 °C for 30 s, 57 °C for 30 s, and 72 °C for 30 s; and 72 °C for 5 min. The wild-type reaction produces a 120-bp product, whereas the mutant reaction produces a 127-bp fragment (Fig. 1). The CF22 primers were used as internal control primers and produce a 578-bp fragment in each reaction. Statistical analysis was performed using the Z-test for two independent proportions. Statistical significance was set at Z 1.96. Of the 120 healthy Irish participants, 56 were heterozygous carriers, giving a genotype frequency of 46.7%, whereas 11 (14.2%) were homozygous for A1298C. Of the MTHFR C677T/A1298C genotype combinations, 28 participants (23.3%) were double heterozygotes. The prevalence of 1298CC homozygotes in this Irish study is significantly higher than that reported for most European populations, including a UK study (Z 1.97) (7 ), an Italian cohort (Z 2.51) (8 ), and an American study (Z 1.99) (9 ). Only two studies from Northern Scotland (10, 11) have reported a higher prevalence. The results of the ARMS PCR were in complete concordance with the results obtained by standard PCRRFLP. The ability of the ARMS PCR to distinguish between genotypes for the A1298C mutation is much higher than that of the standard method.