Lymphocytopenia during the COVID-19 has been associated with fatality. We tested whether pre-existing lymphocytopenia reported prior to any possible exposure to SARS-COV2 (from 2010 to 2019) was associated with fatality. Using all patients diagnosed on testing in a single regional laboratory, we identified 1137 subjects with PCR positive for SARS-COV2 and at least one available complete blood count from the decade prior to any possible exposure to the virus. Bivariate analysis indicated an

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... iation between pre-existing lymphocytopenia (defined as absolute lymphocyte count <0.9x109 /L) and fatality (18% versus 4%). Furthermore, a logistic regression model, accounting for both patient age and number of blood counts obtained, indicated the subjects with pre-existing lymphocytopenia were 1.4 times as likely to die. Because the absolute lymphocyte count is almost universally available and easily interpreted, this biomarker of the risk of fatality could be widely useful.