[Effectiveness of convalescent plasma for treatment of coronavirus disease 2019 patients]

To evaluate the effectiveness and safety of convalescent plasma therapy in patients with severe and critical coronavirus disease 2019 (COVID-19).

Plasma of 200-400 mL was collected from convalescent patients 2 weeks after being discharged from the hospital. After viral nucleic acid testing and antibody testing, the plasma was infused into 16 severe or critical COVID-19 patients. Time for viral nucleic acid amplification (NAA) test turning negative, total volume of plasma transfusion, average antibody concentration, and total antibody amount were recorded. White blood cell (WBC) counts, lymphocyte (LYM) counts, neutrophil (NEU) counts, alanine aminotransferase (ALT), aspartate aminotransferase (AST), C-reactive protein (CRP), procalcitonin (PCT), lactate dehydrogenase (LDH), creatine kinase (CK), creatine kinase isoenzyme (CK-MB), hypersensitive cardiac troponin T (hs-cTnT), and lactic acid (Lac) levels were measured and the rate of change was calculated at the baseline (d0) before plasma transfusion, and day 1 (d1), day 3 (d3) after transfusion.

(1) Patient characteristics: among the 16 patients, 5 cases (31.25%) were severe COVID-19, and 11 cases (68.75%) were critical COVID-19; 62.50% (10/16) of the patients had primary disease; the percentage of invasive ventilation and use of extracorporeal membrane pulmonary oxygenation (ECMO) in critical patients were 90.91% (10/11) and 45.46% (5/11) respectively. (2) Antibody concentration of convalescent plasma and time for NAA test turning negative: the convalescent plasma antibody concentration in this study was ranged from 10.93 kAU/L to 114.7 kAU/L, with an average value of (56.44±39.40) kAU/L. NAA test was continuously positive before plasma transfusion in 10 patients, and the time for NAA test turning negative could be counted. Eight patients turned negative from day 2 to day 8 after transfusion. Severe patients showed a shorter time for NAA test turning negative than critical patients after transfusion [2 (2-3) vs. 5 (3-8), P = 0.036]. Two critical patients transfused plasma with lower antibody concentration remained a positive result of NAA test, and died on the 3rd and 6th day respectively. (3) Laboratory results: the change rates of WBC (0.81±0.28 vs. 1.00) and NEU (0.75±0.33 vs. 1.00) were significantly decreased at d1 after convalescent plasma treatment (both P < 0.05), and the CRP level decreased to about 63% of that before transfusion (P = 0.017). No adverse events were observed during convalescent plasma transfusion.

Viral NAA test of most patients with COVID-19 who received convalescent plasma transfusion turned negative from day 2 to day 8 after transfusion, and the turning time of severe patients was shorter than that of critical patients. Convalescent plasma therapy can reduce the patients' CRP level, and no adverse events were found during the treatment. The antibody concentration in the convalescent plasma may be one of the factors that affect the time for the nucleic acid turning negative after transfusion. Detection and screening convalescent plasma of high-titer antibody and early application to severe and critical patients are expected to improve the efficacy of convalescent plasma.