Delayed-Phase Thrombocytopenia in Patients of Coronavirus Disease 2019 (COVID-19)

The pandemic COVID-19 pneumonia has engulfed the entire world. Hematopoietic system can also be affected by COVID-19. Thrombocytopenia at admission was prevalent, while late-phase or delayed-phase thrombocytopenia is obscure. This retrospective single-center case series analyzed patients with COVID-19 at the Union Hospital, Wuhan, China, from January 25th to March 9th, 2020. Analysis began on March 11th, 2020. COVID-19 associated delayed-phase thrombocytopenia was occurred in 11.8% percent of enrolled patients. The delayed-phase thrombocytopenia in COVID-19 is prone to develop in elderly patients or patients with low lymphocyte count on admission. The delayed-phase thrombocytopenia is significantly associated with increased length of hospital stay and higher ICU admission rate. Delayed-phase nadir platelet counts demonstrated a high and significantly negative linear correlation with B cell percentages and serum IL-6 levels. We also presented bone marrow aspiration pathology of three patients with delayed-phase thrombocytopenia, showing impaired maturation of megakaryocytes. We speculated that the delayed-phase platelet destruction might be mediated by antibodies, and suggest immunoregulatory treatment in severe patients to improve outcomes. Besides, clinicians need to pay attention to the delayed-phase thrombocytopenia especially at 3-4 weeks after symptom onset.