Validation and performance comparison of three SARS-CoV-2 antibody assays.

Serology testing of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is increasingly being used during the current pandemic of coronavirus disease 2019 (COVID-19), although its clinical and epidemiologic utilities are still debatable. Characterizing these assays provides scientific basis to best use them. The current study assessed one chemiluminescent assay (Abbott COVID-2 IgG) and two lateral flow assays (STANDARD Q [SQ] IgM/IgG Duo and Wondfo total antibody test) using 113 blood samples from 71 PCR-confirmed COVID-19 hospitalized patients, 119 samples with potential cross-reactions, and 1068 negative controls including 942 pre-pandemic samples. SARS-CoV-2 IgM antibodies became detectable 3-4 days post-symptom onset using SQ IgM test and IgG antibodies were first detected 5-6 days post-onset using SQ IgG. Abbott IgG and Wondfo Total were able to detect antibodies 7 to 8 days post-onset. After 14 days post-symptom onset, the SQ IgG, Abbott IgG and Wondfo Total tests were able to detect antibodies from 100% of the PCR-confirmed patients in this series; 87.5% sensitivity for SQ IgM. Overall agreement was 88.5% between SQ IgM/IgG and Wondfo Total and 94.6% between SQ IgG and Abbott IgG. No cross-reaction due to recent sera with three of the endemic coronaviruses was observed. Viral hepatitis and autoimmune samples were the main source of limited cross-reactions. The specificities were 100% for SQ IgG and Wondfo Total, 99.62% for Abbott IgG, and 98.87% for SQ IgM. These findings demonstrated high sensitivity and specificity of appropriately validated SARS-CoV-2 serologic assays with implications for clinical use and epidemiological seroprevalence studies.

Cytomorphology of intraductal papillary neoplasm of the biliary tract.

Intraductal papillary neoplasms of the bile duct (IPNBs) are papillary epithelial proliferations with delicate fibrovascular cores within dilated bile ducts. They are thought to be premalignant lesions with potential to progress invasive tumors. To our knowledge, there are no prior descriptions of IPNB cytomorphology. A 58-year-old male presented with painless jaundice and elevated liver function tests was found to have an intraluminal mass within the left hepatic duct. A bile duct brushing diagnosed as "atypical cells present" showed a cellular specimen composed of papillary groups and linear strips of mostly cuboidal/columnar cells with mild atypia and vacuolated cytoplasm. A left hepatic lobectomy including extrahepatic bile ducts showed the mass consisted of papillary cores lined by pancreatobiliary-type epithelium with mild-to-severe atypia, consistent with IPNB with a focus suspicious for invasion. The cytomorphologic features described in the current case suggest intraductal papillary neoplasm but may not be specific since similar features could be seen in other bile duct tumors and even in nonneoplastic conditions such as stent or cholelithiasis. However, it is worthwhile to report papillary hyperplasia with atypia in common bile duct brushings in order to avoid a false-negative diagnosis, especially in the context of a filling defect by images which does not appear to be a stone.