ABSTRACT
Background: Clinical and pathological features of vaccine induced immune thrombotic thrombocytopenia (VITT) following first dose ChAdOx1 nCoV19 vaccination (AZD1222) are well described. VITT post 2nd dose AZD1222 is not widely recognised however its plausible undiagnosed platelet activating antibodies formed after dose 1 may be boosted upon subsequent exposure. (Greinacher et al). Aim(s): We describe the clinicopathological features of suspected VITT post 2nd dose AZD1222 in Australia. Method(s): We conducted a prospective cohort study capturing sequential requests for confirmatory testing for suspected VITT after 2nd dose AZD1222. Testing was based upon key clinicopathological features: Thrombosis within timeframe (4-42 days), thrombocytopenia, D-Dimer >5xULN. High probability VITT (all criteria) underwent immunoassay Asserachrom HPIA IgG (Diagnostica Stago) and functional assay (serotonin release assay or procoagulant flow cytometry). Confirmed VITT cases were compared with those presenting after first dose AZD1222. Descriptive and comparative statistics were performed using SAS studio version 9.4. Result(s): 35 high probability VITT cases presented at a median of 14 days (IQR 9,18) post 2nd dose with platelet count 116 x 109/L (IQR 92, 139) and 14.5 fold increase in D-dimer (IQR 9.4,28.8) were tested. Median dose interval was 84 days (range 25-100), age 70 years (IQR 62, 78) with a male predominance of 66%. Platelet count and D-dimer fold change were less severe compared to cases post 1st dose (Table 1). PF4 antibodies by ELISA were detected in 4 (11%) and antibody mediated platelet activation demonstrable in 19 (54%). These cases were classified as confirmed VITT. Three catastrophic cases including 2 fatalities occurred (Graph 2). Concomitant factors were present in all and influenced outcome severity. Conclusion(s): We describe the largest cohort of suspected VITT post 2nd dose AZD1222. Confirmed cases are similar to those post D1 but platelet count and D-Dimer changes were milder. Similarly, catastrophic cases occurred however concomitant factors were present in all including shorter dosing intervals. (Table Presented).
ABSTRACT
BACKGROUND: Barts Health National Health Service Trust (BHNHST) serves a diverse population of 2.5 million people in London, UK. We undertook a health services assessment of factors used to evaluate the risk of severe acute respiratory coronavirus 2 (SARS-CoV-2) infection.METHODS: Patients with confirmed polymerase chain reaction (PCR) test results admitted between 1 March and 1 August 2020 were included, alongwith clinician-diagnosed suspected cases. Prognostic factors from the 4C Mortality score and 4C Deterioration scores were extracted from electronic health records and logistic regression was used to quantify the strength of association with 28-day mortality and clinical deterioration using national death registry linkage.RESULTS: Of 2783 patients, 1621 had a confirmed diagnosis, of whom 61% were male and 54% were from Black and Minority Ethnic groups; 26% died within 28 days of admission. Mortality was strongly associated with older age. The 4C mortality score had good stratification of risk with a calibration slope of 1.14 (95% CI 1.01-1.27). It may have under-estimated mortality risk in those with a high respiratory rate or requiring oxygen.CONCLUSION: Patients in this diverse patient cohort had similar mortality associated with prognostic factors to the 4C score derivation sample, but survival might be poorer in those with respiratory failure.