Research Subjects

At Washington University School of Medicine, we included plasma samples from patients presenting to the hospital with COVID-19 between March 26, 2020 to May 9, 2020 (‘WUSM cohort’) (6). Diagnosis of COVID-19 was based on a positive nasopharyngeal swab test. Inclusion criteria required that patients be symptomatic and have a physician-ordered SARS-CoV-2 nasopharyngeal swab test performed in the course of their normal clinical care. The first available sample from the patient was utilized for analysis, primarily within 24 hours of hospital admission. 95% (127/134) of samples assessed for sC5b-9 at WUSM were collected within 24 hours of admission. The other 7 samples were included because they were the earliest available samples for those patients in this cohort. Even after excluding these 7 samples, sC5b-9 levels were significantly higher in those patients needing invasive mechanical ventilation (p=0.025). All samples in which Factor B, Ba, C5a and Factor D were assessed, were collected within 24 hours of admission. Other clinically relevant medical information was collected at the time of enrollment from the patient, their legally authorized representative, or the medical record.

We also report findings from influenza-infected patients enrolled in separate, ongoing studies (i.e., EDFLU study) (58). These patients were sampled between 2017-2020, although most were enrolled during the 2019 to 2020 influenza season, prior to the spread of COVID-19 in the St. Louis region.

To have a comparable cohort of patients with non-COVID acute respiratory failure requiring invasive mechanical ventilation, we utilized samples from the ongoing IPS (Immunity in Pneumonia and Sepsis) study at WUSM. These samples were also collected from 2019-2020 among patients admitted to the ICU, on mechanical ventilation, prior to the spread of COVID-19 in the Saint Louis region.

At Yale School of Medicine, plasma samples from 23 patients with COVID-19 were collected between April 13, 2020 to April 24, 2020 (‘Yale longitudinal cohort’) (59, 60). A second Yale cohort (‘Yale cross-sectional cohort’) was also analyzed, which included blood samples obtained either on day 1 (within 24 hours), day 4, and/or day 7 of hospitalization from 49 consecutive adult patients who were admitted for treatment of laboratory-confirmed COVID-19 between May 23, 2020 and May 28, 2020 and remained hospitalized until at least day 4. Diagnosis of COVID-19 was based on a positive nasopharyngeal swab test using PCR assays. Inclusion criteria required that patients be hospitalized and had a physician-ordered SARS-CoV-2 nasopharyngeal swab test performed in the course of their normal clinical care.