Evaluation of Four Rapid Antigen Tests for the Detection of SARS-CoV-2 Infection with Nasopharyngeal Swabs.

Owing to the high transmissibility of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants, the capacity of testing systems based on the gold standard real-time reverse transcription-polymerase chain reaction (rRT-PCR) is limited. Rapid antigen tests (RATs) can substantially contribute to the prevention of community transmission, but their further assessment is required. Here, using 1503 nasopharyngeal swabs, we compared the diagnostic performance of four RAT kits (Abbott Panbio™ COVID-19 Ag Rapid Test, SD Biosensor Standard™ Q COVID-19 Ag Test, Humasis COVID-19 Ag Test, and SG Medical Acrosis COVID-19 Ag Test) to the cycle threshold (Ct) values obtained from rRT-PCR. The precision values, area under the curve values, SARS-CoV-2 variant detection ability, and non-SARS-CoV-2 specificity of all four kits were similar. An assay using the Acrosis kit had a significantly better positive detection rate with a higher recall value and cut-off value than that using the other three RAT kits. During the current COVID-19 pandemic, the Acrosis kit is an effective tool to prevent the spread of SARS-CoV-2 in communities.

Development of an efficient Sanger sequencing-based assay for detecting SARS-CoV-2 spike mutations.

Novel strains of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) harboring nucleotide changes (mutations) in the spike gene have emerged and are spreading rapidly. These mutations are associated with SARS-CoV-2 transmissibility, virulence, or resistance to some neutralizing antibodies. Thus, the accurate detection of spike mutants is crucial for controlling SARS-CoV-2 transmission and identifying neutralizing antibody-resistance caused by amino acid changes in the receptor-binding domain. Here, we developed five SARS-CoV-2 spike gene primer pairs (5-SSG primer assay; 69S, 144S, 417S, 484S, and 570S) and verified their ability to detect nine key spike mutations (ΔH69/V70, T95I, G142D, ΔY144, K417T/N, L452R, E484K/Q, N501Y, and H655Y) using a Sanger sequencing-based assay. The 5-SSG primer assay showed 100% specificity and a conservative limit of detection with a median tissue culture infective dose (TCID50) values of 1.4 × 102 TCID50/mL. The accuracy of the 5-SSG primer assay was confirmed by next generation sequencing. The results of these two approaches showed 100% consistency. Taken together, the ability of the 5-SSG primer assay to accurately detect key SARS-CoV-2 spike mutants is reliable. Thus, it is a useful tool for detecting SARS-CoV-2 spike gene mutants in a clinical setting, thereby helping to improve the management of patients with COVID-19.

Validation and optimization of the Ion Torrent S5 XL sequencer and Oncomine workflow for BRCA1 and BRCA2 genetic testing.

In this study, we validated the analytical performance of BRCA1/2 sequencing using Ion Torrent's new bench-top sequencer with amplicon panel with optimized bioinformatics pipelines. Using 43 samples that were previously validated by Illumina's MiSeq platform and/or by Sanger sequencing/multiplex ligation-dependent probe amplification, we amplified the target with the Oncomine™ BRCA Research Assay and sequenced on Ion Torrent S5 XL (Thermo Fisher Scientific, Waltham, MA, USA). We compared two bioinformatics pipelines for optimal processing of S5 XL sequence data: the Torrent Suite with a plug-in Torrent Variant Caller (Thermo Fisher Scientific), and commercial NextGENe software (Softgenetics, State College, PA, USA). All expected 681 single nucleotide variants, 15 small indels, and three copy number variants were correctly called, except one common variant adjacent to a rare variant on the primer-binding site. The sensitivity, specificity, false positive rate, and accuracy for detection of single nucleotide variant and small indels of S5 XL sequencing were 99.85%, 100%, 0%, and 99.99% for the Torrent Variant Caller and 99.85%, 99.99%, 0.14%, and 99.99% for NextGENe, respectively. The reproducibility of variant calling was 100%, and the precision of variant frequency also showed good performance with coefficients of variation between 0.32 and 5.29%. We obtained highly accurate data through uniform and sufficient coverage depth over all target regions and through optimization of the bioinformatics pipeline. We confirmed that our platform is accurate and practical for diagnostic BRCA1/2 testing in a clinical laboratory.

Routine chromosomal microarray analysis is necessary in Korean patients with unexplained developmental delay/mental retardation/autism spectrum disorder.

BACKGROUND: All over the world, chromosomal microarray (CMA) is now the first tier diagnostic assay for genetic testing to evaluate developmental delay (DD), mental retardation (MR), and autism spectrum disorder (ASD) with unknown etiology. The average diagnostic yield of the CMA test is known to be about 12.2%, while that of conventional G-banding karyotype is below 3%. This study aimed to assess the usefulness of CMA for the purpose of clinical diagnostic testing in the Korean population. METHODS: We performed CMA and multiplex ligation-dependent probe amplification (MLPA) tests in 96 patients with normal karyotype and unexplained DD, MR, or ASD. The CMA was conducted with CytoScan 750K array (Affymetrix, USA) with an average resolution of 100 kb. RESULTS: Pathogenic copy number variations (CNVs) were detected in 15 patients by CMA and in two patients by MLPA for four known microdeletion syndromes (Prader-Willi/Angelman syndrome, DiGeorge syndrome, Miller-Dieker syndrome and Williams syndrome) designated by National Health Insurance system in Korea. The diagnostic yield was 15.6% and 2.1%, respectively. Thirteen (13.5%) patients (excluding cases with pathogenic CNVs) had variants of uncertain clinical significance. There was one patient with a 17.1-megabase (Mb) region of homozygosity on chromosome 4q. CONCLUSIONS: Our findings suggest the necessity of CMA as a routine diagnostic test for unexplained DD, MR, and ASD in Korea.

Breakpoint mapping by whole genome sequencing identifies PTH2R gene disruption in a patient with midline craniosynostosis and a de novo balanced chromosomal rearrangement.

BACKGROUND: Craniosynostosis (CRS) is a premature closure of calvarial sutures caused by gene mutation or environmental factors or interaction between the two. Only a small proportion of non-syndromic CRS (NSC) patients have a known genetic cause, and thus, it would be meaningful to search for a causative gene disruption for the development NSC. We applied a whole genome sequencing approach on a 15-month-old boy with sagittal and metopic synostosis to identify a gene responsible for the development of the disease. METHODS AND RESULTS: Conventional chromosome study revealed a complex paracentric inversion involving 2q14.3 and 2q34. Array comparative genomic hybridisation did not show any copy number variation. Multicolour banding analysis was carried out and the breakpoints were refined to 2q14 and 2q34. An intronic break of the PTH2R gene was detected by whole genome sequencing and fluorescence in situ hybridisation analysis confirmed disruption of PTH2R. CONCLUSIONS: We report PTH2R as a gene that is disrupted in NSC. The disruption of the PTH2R gene may cause uncontrolled proliferation and differentiation of chondrocytes, which in turn results in premature closure of sutures. This addition of PTH2R to the list of genes associated with NSC expands our understanding of the development of NSC.

Evaluation of the optimal neutrophil gelatinase-associated lipocalin value as a screening biomarker for urinary tract infections in children.

BACKGROUND: Neutrophil gelatinase-associated lipocalin (NGAL) is a promising biomarker in the detection of kidney injury. Early diagnosis of urinary tract infection (UTI), one of the most common infections in children, is important in order to avert long-term consequences. We assessed whether serum NGAL (sNGAL) or urine NGAL (uNGAL) would be reliable markers of UTI and evaluated the appropriate diagnostic cutoff value for the screening of UTI in children. METHODS: A total of 812 urine specimens and 323 serum samples, collected from pediatric patients, were analyzed. UTI was diagnosed on the basis of culture results and symptoms reported by the patients. NGAL values were measured by using ELISA. RESULTS: NGAL values were more elevated in the UTI cases than in the non-UTI cases, but the difference between the values were not statistically significant (P=0.190 for sNGAL and P=0.064 for uNGAL). The optimal diagnostic cutoff values of sNGAL and uNGAL for UTI screening were 65.25 ng/mL and 5.75 ng/mL, respectively. CONCLUSIONS: We suggest that it is not appropriate to use NGAL as a marker for early diagnosis of UTI in children.

The first Korean case of candidemia due to Candida dubliniensis.

Candidemia due to uncommon Candida spp. appears to be increasing in incidence. C. dubliniensis has been increasingly recovered from individuals not infected with HIV. Identification of C. dubliniensis can be problematic in routine clinical practice due to its phenotypic resemblance to C. albicans. We report the first case of C. dubliniensis candidemia in Korea, which occurred in a 64-yr-old woman who presented with partial seizure, drowsiness, and recurrent fever. Germ-tube positive yeast that was isolated from blood and central venous catheter tip cultures formed smooth, white colonies on sheep blood agar and Sabouraud agar plates, indicative of Candida spp. C. dubliniensis was identified using the Vitek 2 system (bioMerieux, USA), latex agglutination, chromogenic agar, and multiplex PCR. The blood isolate was susceptible to flucytosine, fluconazole, voriconazole, and amphotericin B. After removal of the central venous catheter and initiation of fluconazole treatment, the patient's condition gradually improved, and she was cleared for discharge from our hospital. Both clinicians and microbiologists should be aware of predisposing factors to C. dubliniensis candidemia in order to promote early diagnosis and appropriate treatment.

Development of acute megakaryoblastic leukemia with isochromosome (12p) after a primary mediastinal germ cell tumor in Korea.

The association of hematological malignancies with a mediastinal germ cell tumor (GCT) is very rare. We report one case of a young adult male with primary mediastinal GCT who subsequently developed acute megakaryoblastic leukemia involving isochromosome (12p). A 25-yr-old man had been diagnosed with a mediastinal GCT and underwent surgical resection and adjuvant chemotherapy. At 1 week after the last cycle of chemotherapy, his peripheral blood showed leukocytosis with blasts. A bone marrow study confirmed the acute megakaryoblastic leukemia. A cytogenetic study revealed a complex karyotype with i(12p). Although additional chemotherapy was administered, the patient could not attain remission and died of septic shock. This case was definitely distinct from therapy-related secondary leukemia in terms of clinical, morphologic, and cytogenetic features. To our knowledge, this is the first case report of a patient with mediastinal GCT subsequently developing acute megakaryoblastic leukemia involving i(12p) in Korea.

A case of paraneoplastic nephrotic syndrome in a patient with ovarian carcinoma.

Nephrotic syndrome is a rare manifestation of malignancy associated with paraneoplastic syndrome. Paraneoplastic nephrotic syndrome has been reported in various malignancies: malignant lymphoma, colon cancer, lung cancer and prostate cancer. However, an ovarian carcinoma associated with nephrotic syndrome has rarely been reported. Only six cases of ovarian carcinoma associated paraneoplastic nephrotic syndrome has been reported worldwide, but no cases have been reported in Korea. Here, we report a case of paraneoplastic nephrotic syndrome in a patient with an ovarian carcinoma. The patient presented with ascites, proteinuria and hypoalbuminemia. An initial computed tomography (CT) scan and ultrasonography evaluations showed no specific findings suggestive of an ovarian tumor. Despite treatment for nephrotic syndrome, the symptoms became more aggravated. There after, follow up evaluation at Yonsei University Medical Center, including serum CA 125, pelvis MRI and peritoneal fluid examination were performed. On the pelvis MRI, a left ovarian mass was detected with an ascitic fluid collection. The serum CA 125 level was elevated to 2211 U/ml. The peritoneal fluid cytological examination showed malignant cells suggestive of an ovarian carcinoma. Combination chemotherapies including paclitaxel plus carboplatin, topotecan plus gemcitabine and oxaliplatin plus capecitabine were administered to the patient, and complete remission was achieved on image and tumor marker studies. There was complete recovery from the nephrotic syndrome with no evidence of ascites and proteinuria. These findings suggest that nephrotic syndrome caused by paraneoplastic syndrome can be resolved only after the complete control of the underlying malignancy.

The Effect of ZD 1839 (Iressa(R)) in the Treatment of Refractory Non Small Cell Lung Cancer.

PURPOSE: The aim of this study was to evaluate the efficacy and the safety of ZD 1839 (Iressa(R)) as a 3rd or 4th line chemotherapy regimen in NSCLC patients who are refractory to a previous chemotherapy regimen. MATERIALS AND METHODS: Twenty-five patients who were refractory to previous chemotherapy were selected for this study. The eligible patients had an ECOG performance status of 0 to 2, and an appropriate end organ function. ZD 1839 (Iressa(R))250 mg/d was orally administered until the patients experienced disease progression or unacceptable toxicity. RESULTS: Twenty-five patients were analyzed. The median age of the patients was 57 years. The response rate was 12.0% with partial responses in 3 patients. Fourteen patients (56%) remained in the stable disease state and 8 patients progressed. The median overall survival was 9.0 months (95% CI 6.7~11.2). The median progression free survival was 3 months (95% CI 2.2~3.8). Hematological toxicities of grade 3 or 4 neutropenia, anemia and thrombocytopenia were absent. Non-hematological toxicities were grade 2 or 3 skin rashes in 10 (40.0%) patients and 1 (4.0%) patient and grade 3 nausea in 3 (12.0%) patients. No patient failed to continue chemotherapy due to any drug-related adverse events. CONCLUSION: The results suggest that ZD 1839 (Iressa(R)) monotherapy is effective and tolerable as a 3rd or 4th line salvage treatment for NSCLC patients refractory to previous chemotherapy regimens.