Performance of LIFECODES HLA-DQB1 Typing Kit Using Luminex Platform in Koreans

Intermediate-resolution HLA-DQ typing has gained importance in organ transplantation recently. We evaluated the performance of the LIFECODES HLA-DQB1 typing kit (Immucor, USA) using sequence-specific oligonucleotide (SSO) probe and Luminex platform (Luminex Corp., USA) on 100 samples tested by sequence-based typing (SBT) using the AlleleSEQR HLA-DQB1 kit (Abbott Molecular, USA) in Korean individuals. No sample showed ambiguity in the assignment of 4-digit HLA-DQB1 allele with the LIFECODES HLA-DQB1 SSO typing kit, and the results were fully concordant with those of high-resolution typing of AlleleSEQR HLA-DQB1 SBT up to 4-digit level. Three samples required adjustment of false reactions (3/100, 3.0%): two samples with DQB1*03:03/*06:01 showed false-positive result in probe 253, and 1 sample with DQB1*04:02/*05:02 showed false-negative result in probe 217. We tested an additional sample with DQB1*03:03/*06:01, which showed same false-positivity in probe 253 and 2 samples with DQB1*04:02/*05:02, which showed no false reaction. The false reactions did not result in ambiguity or change in the HLA allele assignment. We could assign HLA-DQB1 alleles to 4 digit-level without ambiguity, with 100% concordance with the SBT results. Thus, LIFECODES HLA-DQB1 SSO typing kit showed good performance for intermediate-resolution HLA-DQB1 typing in clinical laboratory for organ transplantation in Koreans.

Evaluation of the Anyplex BRAF V600E Real-Time Detection Assay Using Dual-Priming Oligonucleotide Technology in Fine-Needle Aspirates of Thyroid Nodules

BACKGROUND: Several molecular assays have been developed to detect the BRAF V600E mutation in fine needle aspirates (FNAs) for the diagnosis of papillary thyroid cancer. Using a multiplex PCR technique, we evaluated the Anyplex BRAF V600E Real-time Detection (Anyplex) assay and compared its efficacy with that of the Seeplex BRAF V600E ACE Detection (Seeplex) method. METHODS: We tested 258 consecutive FNA specimens using the Seeplex and Anyplex assays. Any conflicting results between the two assays were confirmed by using mutant enrichment with 3'-modified oligonucleotide (MEMO) sequencing. The limits of detection (LODs) and reproducibility for each assay were evaluated with serially diluted DNA from a BRAF V600E-positive cell line. RESULTS: The BRAF V600E mutation was detected in 36.4% (94/258) FNA specimens by either the Seeplex or Anyplex assay. Results for the two assays showed 93.4% (241/258) agreement, with a kappa value of 0.861 (95% confidence interval, 0.798-0.923). Of the eight specimens that were BRAF V600E-positive by the Anyplex assay but not by the Seeplex assay, five were found to be BRAF V600E-positive by MEMO sequencing. The mutation detection rate of the Seeplex and Anyplex assays was 79.0% and 84.0%, respectively, in the FNA specimens diagnosed as malignant (n=81). The LOD as determined by probit analysis was 0.046% (95% confidence interval, 0.019-0.532%). CONCLUSIONS: The Anyplex assay performed better than the Seeplex assay with respect to the detection of the BRAF V600E mutation.

Multiplex PCR for Rapid Detection of Genes Encoding Class A Carbapenemases

In recent years, there have been increasing reports of KPC-producing Klebsiella pneumoniae in Korea. The modified Hodge test can be used as a phenotypic screening test for class A carbapenamase (CAC)-producing clinical isolates; however, it does not distinguish between carbapenemase types. The confirmation of type of CAC is important to ensure optimal therapy and to prevent transmission. This study applied a novel multiplex PCR assay to detect and differentiate CAC genes in a single reaction. Four primer pairs were designed to amplify fragments encoding 4 CAC families (SME, IMI/NMC-A, KPC, and GES). The multiplex PCR detected all genes tested for 4 CAC families that could be differentiated by fragment size according to gene type. This multiplex PCR offers a simple and useful approach for detecting and distinguishing CAC genes in carbapenem-resistant strains that are metallo-beta-lactamase nonproducers.

Analysis of DNA polymerase activity in vitro using non-radioactive primer extension assay in an automated DNA sequencer

Although different DNA polymerases have distinct functions and substrate affinities, their general mechanism of action is similar. Thus, they can all be studied using the same technical principle, the primer extension assay employing radioactive tags. Even though fluorescence has been used routinely for many years for DNA sequencing, it has not been used in the in vitro primer extension assay. The use of fluorescence labels has obvious advantages over radioactivity, including safety, speed and ease of manipulation. In the present study, we demonstrated the potential of non-radioactive in vitro primer extension for DNA polymerase studies. By using an M13 tag in the substrate, we can use the same fluorescent M13 primer to study different substrate sequences. This technique allows quantification of the DNA polymerase activity of the Klenow fragment using different templates and under different conditions with similar sensitivity to the radioactive assay.