Optimization of a Low-Cost, Sensitive PNA Clamping PCR Method for JAK2 V617F Variant Detection

Background: The JAK2 V617F variant is diagnostic for myeloproliferative neoplasms, a group of clonal disorders of hematopoietic stem and progenitor cells. Although several approaches have been developed to detect the variant, a gold standard diagnostic method has not yet been defined. We describe a simple, fast, and cost-effective PCR-based approach that enhances test specificity and sensitivity by blocking the amplification of the large excess of wild-type DNA. Methods: The method involves using an oligo peptide nucleic acid (PNA) perfectly matching its corresponding DNA sequence. The PCR protocol was optimized by collecting a detailed thermodynamic data set on PNA-DNA wild-type duplexes by circular dichroism melting experiments. The specificity and sensitivity of PNA clamping PCR were assessed by genotyping 50 patients with myeloproliferative neoplasm who carried the JAK2 V617F variant and 50 healthy donors. Results: The optimized protocol enabled selective amplification of the variant alleles, achieving maximum sensitivity (100%) and specificity (100%). Analytical sensitivity was 0.05% of variant alleles as assessed by serial dilutions of DNA from the HEL cell line (which carries the JAK2 V617F variant) mixed to wild-type DNA from healthy donors. The JAK2 V617F variant test performed according to this method has better diagnostic performance than its 2 main PCR-based competitors, at much lower cost. Conclusions: High sensitivity and specificity and cost-effectiveness make PNA clamping PCR a useful testing platform for the detection of minor allele variants in small-scale diagnostic laboratories. It promises to improve patient care while enabling significant healthcare savings

Seroprevalence of SARS-CoV-2 assessed by four chemiluminescence immunoassays and one immunocromatography test for SARS-Cov-2

The onset of the new SARS-CoV-2 coronavirus encouraged the development of new serologic tests that could be additional and complementary to Real Time RT-PCR based assays. In such a context, the study of performances of available tests is urgently needed, as their use has just been initiated for seroprevalence assessment. The aim of this study was to compare four chemiluminescence immunoassays and one immunocromatography test for SARS-Cov-2 antibodies for the evaluation of the degree of diffusion of SARS-CoV-2 infection in Salerno Province (Campania Region, Italy). 3185 specimens from citizens were tested for anti-SARS-CoV-2 antibodies as part of a screening program. Four automated immunoassays (Abbott and Liaison SARS-CoV-2 CLIA IgG and Roche and Siemens SARS-CoV-2 CLIA IgM/IgG/IgA assays) and one lateral flow immunoassay (LFIA Technogenetics IgG-IgM COVID-19) were used. Seroprevalence in the entire cohort was 2.41%, 2.10%, 1.82% and 1.85% according to the Liaison IgG, Abbott IgG, Siemens and Roche total Ig tests, respectively. When we explored the agreement among the rapid tests and the serologic assays, we reported good agreement for Abbott, Siemens, and Roche (Cohen’s Kappa coefficient 0.69, 0.67 and 0.67, respectively), whereas we found moderate agreement for Liaison (Cohen’s Kappa coefficient 0.58). Our study showed that Abbott and Liaison SARS-CoV-2 CLIA IgG, Roche and Siemens SARS-CoV-2 CLIA IgM/IgG/IgA assays and LFIA Technogenetics IgG-IgM COVID-19 have good agreement in seroprevalence assessment. In addition, our findings indicate that the prevalence of IgG and total Ig antibodies against SARS-CoV-2 at the time of the study was as low as around 3%, likely explaining the amplitude of the current second wave