CD99, a glycoprotein found on the surfaces of leukocytes and concentrated at the borders of endothelial cells, plays a major role in the migration of leukocytes across endothelial cells into sites of inflammation, and has other roles in thymocyte development. The human and mouse genomes encode only two proteins related to CD99. One of these, XGA, is a red blood cell surface antigen. The function of the other, CD99-like 2 (CD99L2), is not known. We cloned mouse CD99L2 and used CD99L2 isolated from transfected cells to raise specific antibodies. Similar to human CD99, CD99L2 was expressed at the borders between transfected cells as well as on mouse leukocytes and vascular endothelial cells in situ. Transfection of L cell fibroblasts with CD99L2 imparted to them the ability to adhere to each other in a divalent cation-dependent, homophilic manner. Anti-CD99L2 antibody blocked influx of neutrophils and monocytes into a site of inflammation in vivo.

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Objective To estimate the association between COVID-19 and Emergency Department (ED) psychiatric presentations, including suicidal ideation. Methods Using an interrupted time series design, we analyzed psychiatric presentations using electronic health record data in an academic medical center ED between 2018 and 2020. We used regression models to assess the association between the onset of the COVID-19 outbreak and certain psychiatric presentations. The period February 26–March 6, 2020 was used to define patterns in psychiatric presentations before and after the coronavirus outbreak. Results We found a 36.2% decrease (unadjusted) in ED psychiatric consults following the coronavirus outbreak, as compared to the previous year. After accounting for underlying trends, our results estimate significant differential change associated with suicidal ideation and substance use disorder (SUD) presentations following the outbreak. Specifically, we noted a significant differential increase in presentations with suicidal ideation six weeks after the outbreak (36.4 percentage points change; 95% CI: 5.3, 67.6). For presentations with SUD, we found a differential increase in the COVID-19 time series relative to the comparison time series at all post-outbreak time points and this differential increase was significant three weeks (32.8 percentage points; 95% CI: 4.0, 61.6) following the outbreak. Our results estimate no differential changes significant at the P value < 0.05 level associated with affective disorder or psychotic disorder presentations in the COVID-19 time series relative to the comparator time series. Conclusions The COVID-19 outbreak in Boston was associated with significant differential increases in ED presentations with suicidal ideation and SUD.

Objective This study aims to detail changes in presentations at a United States Emergency Department for suicidality before and after the outbreak of COVID-19. Methods A retrospective chart review was conducted of all adult patients who presented to an ED with suicidality and underwent psychiatric consultation during the study period. The cohorts consisted of patients who presented between December 2018 – May 2019 and December 2019 – May 2020. Information was collected on demographics, characteristics of suicidality, reasons for suicidality and disposition. The first wave from March – May 2020 was examined, using a difference-in-differences design to control for factors other than COVID-19 that may have influenced the outcomes' trend. Results Immediately following the pandemic outbreak there was a statistically significant increase in the proportion of undomiciled patients represented in visits for suicidality (40.7% vs. 57.4%; p -value <0.001). In addition, the proportion of patient visits attributed to social (18.0% vs. 29.2%; p-value 0.003) and structural (14.2% vs. 26.4%; p value <0.001) reasons for suicidality increased. Conversely, the proportion of visits due to psychiatric symptoms (70.5% vs 50.0%; p -value <0.001) decreased. Furthermore, patient visits were more likely to result in a medical admission (2.1% vs. 8.3%; p -value 0.002) and less likely to result in a psychiatric admission (68.4% vs 48.6%; p-value <0.001) during the initial phase of the pandemic. Conclusions COVID-19 was associated with increased ED presentations for suicidality among undomiciled patients, as well as greater likelihood of social and structural reasons driving suicidality among all visits.

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