Validation of a hospital-acquired venous thrombosis risk assessment model: The medical inpatient thrombosis and hemostasis (MITH) study

Background: To reduce the risk of hospital-acquired venous thrombosis (HA-VTE) in medical patients, guidelines recommend assessing HA-VTE risk and providing prophylaxis for those at high risk. Risk assessment models (RAMS) including objective risk factors available at admission remain an unmet clinical need. Aim(s): To develop and validate a RAM for HA-VTE in medical inpatients using data available to providers within 24-h of hospital admission. Method(s): We developed a HA-VTE RAM at the University of Vermont Medical Center (Burlington, Vermont, USA, Table 1) and validated this RAM at Michigan Medicine (Ann Arbor, Michigan, USA, Table 2). HA-VTE and the risk factors were identified using previously validated computable phenotypes. The RAM was developed using a Bayesian LASSO approach with model performance assessed using area under the receiver operating curves (AUC) and the slope of observed versus expected plot. People admitted with VTE were excluded. The research was approved by the Institutional Review Board funded by the National Institutes of Health and the Centers for Disease Control and Prevention, USA. Result(s): Table 1 presents the risk factors, odds ratios (OR) and 95% credible intervals (CI) for the HA-VTE RAM, which included 11 risk factors. For the development cohort, based on 219 events among 62,468 admissions, the AUC of the model was 0.75 and the observed versus expected slope was 1.11 (Table 2). In the validation cohort there were 48,265 admissions and 363 HA-VTE events with a younger population and a higher incidence of HA-VTE. The AUC and the observed versus expected slope were 0.69 and 0.89 (Table 2). Conclusion(s): We developed and validated a HA-VTE RAM in populations. The model fit and calibration are promising especially given these are two geographically diverse institutions. Further validation is in progress at additional hospitals as well as in people hospitalized with COVID-19.

Use of Non-Approved and Approved Treatments for COVID-19 by CKD Status in Medicare

Background: Hydroxychloroquine, chloroquine, and ivermectin gained popularity for treatment of COVID-19 in 2020. Remdesivir was approved for treating hospitalized COVID-19 in late 2020. We studied the uptake of these drugs early in the pandemic in a 5% sample of Medicare fee-for-service beneficiaries with and without CKD. Method(s): We examined the percentage of beneficiaries receiving >=1 Part D covered prescription for hydroxychloroquine or chloroquine and ivermectin in each month of 2020. Among first COVID-19 hospitalizations from November 2020-June 2021, we examined the percentage receiving remdesivir using ICD-10-PCS. Analyses included those aged >=66 years without ESRD;CKD was defined by >=1 inpatient or >=2 outpatient diagnoses. Result(s): Use of hydroxychloroquine and chloroquine increased in March 2020 and then subsided in the ensuing months, remaining slightly elevated though 2020 (Figure A). Receipt of these drugs was higher in patients with CKD than in those without. Ivermectin use was uncommon in both groups before spiking in December 2020 (Figure B). Among COVID-19 inpatients, 55% without CKD and 44% with CKD received remdesivir, which was used more often in men than in women, less often in Blacks than in Whites or Hispanics, and less often in those with the low-income subsidy than in those without. Conclusion(s): In 2020, Medicare beneficiaries with and without CKD showed similar spiking patterns in use of the approval-revoked or non-approved drugs hydroxychloroquine/chloroquine (in March) and ivermectin (in December). Through June 2021, remdesivir was used less in patients with CKD than in those without for hospitalized COVID-19, likely because the FDA recommends not using remdesivir if eGFR is <30 mL/min. Lower income and Black patients were less likely to receive remdesivir than others.

Undercounting of COVID-19 Vaccinations in Fee-for-Service Medicare Claims

Background: Older individuals and those with certain underlying conditions were among the earliest groups offered COVID-19 vaccinations. While patients with ESKD did not initially receive priority, a federal program permitted vaccinations to be administered in dialysis clinics starting in March 2021. We studied early uptake of COVID-19 vaccinations in Medicare fee-for-service beneficiaries with ESKD. Method(s): We included beneficiaries aged >=18 years with ESKD on December 1, 2020 from the US Renal Data System. Vaccinations covered by Medicare were identified using CPT codes. The cumulative monthly incidence of first vaccination dose through June 2021 was compared by modality (HD, PD, transplant) and stratified by age and race/ ethnicity. Death was treated as a competing risk. Result(s): By June 30, 2021, the cumulative incidence of receiving a Medicare-covered first vaccination dose was <40% in patients receiving HD (Figure A), well under the estimate reported by dialysis facilities to the CDC by this date (72%). Although caution is required, some interpretation of the Medicare vaccination data may still be permitted. After the allocation of vaccines to dialysis clinics, Medicare-covered vaccinations surged in patients receiving HD relative to the other modalities. In patients receiving HD, uptake of Medicare-covered vaccinations was initially highest among those aged >=65 years and then surged in younger patients following the federal vaccine allocation (Figure B). Conclusion(s): COVID-19 vaccination rates are severely underestimated using Medicare administrative data. It is unclear whether missingness of vaccination data is differential by demographic groups, such as race/ethnicity. Inferences based on these data should be made with caution.