CHA Hollywood Presbyterian Medical Center World-renowned Epidemiology Expert Dr. Rohit Varma Co-authors Study to Investigate & Improve Accuracy of COVID-19 Case Fatality Ratios

Through Cross-Country Comparison of COVID-19 Case Fatality Ratios, Researchers Propose Contact Tracing to Mitigate Biases Affecting Case Fatality Ratios and Obtain More Accurate Data to Guide Healthcare Policy Decision Makers

LOS ANGELES–(BUSINESS WIRE)–CHA Hollywood Presbyterian Medical Center (CHA HPMC), a hospital that is a member of CHA Health Systems, a global network providing a full spectrum of dynamic healthcare services, today announced publication of a study co-authored by Rohit Varma, MD, MPH, director of its Southern California Eye Institute, and a team of researchers from the University of California, Berkeley, led by Anastasios Nikolas Angelopoulos, assessing the prevalent biases in COVID-19 case fatality ratios (CFR)—the proportion of deaths among all COVID-19 infected individuals—between population groups to propose contact tracing as a solution to improve the accuracy of CFR to better guide healthcare policy decision making. The study has been published in Harvard Data Science Review.

Through statistical analysis, the researchers show that randomized data obtained through contact tracing—a disease control measure of contacting all people who’ve had close contact with someone who tested positive for COVID-19—can help mitigate the competing biases in time series of deaths, cases, and recoveries affecting CFR to accurately guide policy decisions on medical resource allocation during the pandemic.

“COVID-19 fatality rates are a key indicator of risk when determining policy decisions regarding medical resource allocation during this pandemic. Through this study, we investigate the biases that affect CFR and give a mathematical justification for contact tracing as a powerful data-collection methodology to mitigate the problematic biases at their source and improve accuracy of CFR. Public health organizations and local, state, and national governments must allocate scarce resources to populations especially susceptible to death during this pandemic,” said Angelopoulos.

The researchers utilized open-sourced COVID-19 data from Johns Hopkins University to calculate the relative CFRs for nine countries from April 2 to April 16, 2020. While CFR averages out effects of medical care, age, geography, genetics, and other factors, it is still prone to biases such as under-reporting of mild cases, time lags, interventions, group characteristics, and imperfect reporting and attribution. To minimize these biases, the study proposes contact tracing to expand the sampling frame to include a larger population, regardless of symptoms, which would help reduce data reporting differences between diagnosis and death.

“Contact tracing does not eliminate all biases. However, the population sampled using this strategy would be closer to the target population, since it would include asymptomatic cases. Furthermore, there is no issue with time lag, since these cases can be tracked systematically,” Dr. Varma said. “It is equally important for the statistical community to channel much of its energy into a unified call-to-action for governments to obtain more accurate data estimates to support consequential policy-making.”

An accomplished world-renowned physician-scientist, Dr. Varma has authored or co-authored more than 300 journal articles in peer-reviewed journals and edited or authored three books.

About Southern California Eye Institute

Southern California Eye Institute is dedicated to providing the highest level of vision care, using the latest technology and treatments to deliver the best outcome to patients in Los Angeles and from around the world. The institute’s expert physician-scientists are advancing innovations in stem cell and regenerative therapies, artificial intelligence and bioelectronic implants to further the prevention, early detection and treatment of eye diseases and conditions. Founded by world-renowned ophthalmologist Rohit Varma, MD, MPH, SCEI is located in Los Angeles at CHA Hollywood Presbyterian Medical Center. For more information, visit

About CHA Hollywood Presbyterian Medical Center

CHA Hollywood Presbyterian Medical Center (CHA HPMC) is a nationally recognized acute care facility that has cared for Hollywood and its surrounding communities since 1924. Today, CHA HPMC offers comprehensive health care services with a 434-bed acute care facility, including 89 skilled nursing beds. The hospital has a medical staff of more than 500 physicians and specialists, representing 69 specialties and 75 different countries. CHA HPMC embraces the area’s diverse, multicultural patient populations by providing all who walk through its doors quality care in a compassionate manner. It is a member of CHA Health Systems, a dynamic global healthcare organization that provides a full spectrum of services in seven countries around the world, including 25 hospitals and clinics, 30 research and 14 education institutions and 30 bio/pharmaceutical/healthcare companies. For more information, visit


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