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BackgroundBreakthrough infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant (B.1.1.529) has occurred in populations with high vaccination rates. These infections are due to sequence variation in the spike protein leading to a reduction in protection afforded by the current vaccines, which are based on the original Wuhan-Hu-1 strain, or by natural infection with pre-Omicron strains.MethodsIn a longitudinal cohort study, pre-breakthrough infection sera for Omicron breakthroughs (n=12) were analyzed. Assays utilized include a laboratory-developed solid phase binding assay to recombinant spike protein, a commercial assay to the S1 domain of the spike protein calibrated to the World Health Organization (WHO) standard, and a commercial solid-phase surrogate neutralizing activity (SNA) assay. All assays employed spike protein preparations based on sequences from the Wuhan-Hu-1 strain. Participant demographics and clinical characteristics were captured.ResultsPre-breakthrough binding antibody (bAB) titers ranged from 1:800-1:51,200 for the laboratory-developed binding assay, which correlated well and agreed quantitatively with the commercial spike S1 domain WHO calibrated assay. SNA was detected in 10/12 (83%) samples.ConclusionsNeither high bAB nor SNA were markers of protection from Omicron infection/re-infection. Laboratory tests with antigen targets based on Wuhan-Hu-1 may not accurately reflect the degree of immune protection from variants with significant spike protein differences. Omicron breakthrough infections are likely due to high sequence variation of the spike protein and reflect incomplete immune protection from previous infection with strains that preceded Omicron or with vaccinations based on the original Wuhan-Hu-1 strain.

Background 1,3-β-D-glucan (BDG) is a cell wall component of fungi such as Aspergillus spp., Candida spp., and Pneumocystis jirovecii. BDG assay is used as a screening test to aid early diagnosis of invasive fungal infections (IFI) that are associated with significant morbidity and mortality in immunocompromised patients. The diagnostic performance varies depending on IFI risks among study populations, thus it is important to appropriately select patients with risk factors for IFI to optimize utilization of the BDG test. Figure 1. Figure 2. Methods An intervention to improve BDG test utilization was initiated at Truman Medical Center on November 28, 2018. The BDG test order was replaced by a BDG test request. The request was sent to the inbox of an on-call pathology team. Patient information was reviewed and the on-call pathology team called the ordering physician to discuss the case based on the approval algorithm chart. The criteria for BDG test approval were 1) immunocompromised or ICU patient, and 2) on empiric antifungal therapy, or inability to perform specific diagnostic tests such as bronchoscopy. If approved, a BDG test order was immediately processed. Retrospective chart review was conducted for 1 year pre- and post- intervention to obtain demographic, clinical, and laboratory data for 4 patient groups. Group 1 included patients who had BDG tests during pre-intervention period. Group 2 was composed of all patients who had BDG test requests during post-intervention period. Group 2a and 2b were the post-intervention patients with approved and rejected BDG test requests, respectively. Figure 3. Results The number of BDG tests performed per year decreased from 156 pre-intervention to 24 post-intervention. The number of test requests was 65 and 41 of them were rejected which led to $7,380 direct cost savings. There was no significant difference in age or the proportion of immunocompromised and ICU patients between Group 1 and 2. The test positivity rate was significantly higher in Group 2-a compared to Group 1 (45.8 % vs. 25.3%, p=0.038). There was no delay in IFI diagnosis or IFI-related mortality in patients for whom BDG test requests were rejected. Conclusion We successfully and safely implemented a diagnostic stewardship intervention for BDG testing and improved test utilization. Disclosures All Authors: No reported disclosures

Abdominal lymphangiectasia is a rare disease manifestation with a variety of anatomic locations and clinical presentations. The gastrointestinal tract may be affected, and lymphangiectasia originating in the wall of the intestine has rarely been described. We present a case of primary small bowel lymphangiectasia causing intussusception in a 30-year-old woman who presented with emesis and gastrointestinal bleeding. This case emphasizes the clinical presentation, diagnosis, and management in adults with abdominal lymphangiectasia. We highlight the importance of a high clinical suspicion for lymphangiectasia in an adult with acute abdomen to avoid catastrophic morbidity.

An Atypical Fibroxanthoma (AFX) is a benign skin tumor of mesenchymal origin most commonly found on the sun-exposed or radiation-damaged skin of the elderly. AFX may share many common histologic and clinical characteristics with squamous cell carcinoma and melanoma; however, it is a benign process. Therefore, differentiating between these lesions is important. Differences in histologic features and patterns of immunohistochemical staining for CD68, CD10, cytokeratins, S-100 and Fi-67 may diagnose AFX. The presence of an AFX on the conjunctiva is rare with only five other reported cases. We report a case of AFX that developed in the bulbar conjunctiva near the limbus.