Retrospective analysis on efficacy of convalescent plasma in acute respiratory distress syndrome due to COVID-19

ABSTRACT BACKGROUND: Coronavirus disease 2019 (COVID-19) is an ongoing global health threat. However, currently, no standard therapy has been approved for the disease. OBJECTIVES: To evaluate the clinical effectiveness of convalescent plasma (CP) in patients with acute respiratory distress syndrome (ARDS) due to COVID-19. DESIGN AND SETTING: Retrospective study conducted at Kayseri City Education and Research Hospital, Kayseri, Turkey. METHODS: The case group consisted of adult patients (> 18 years) with ARDS due to COVID-19 who received CP in combination with antiviral and supportive treatment. These patients were compared with others who only received antiviral and supportive treatment. RESULTS: During the study period, a total of 30 patients with ARDS due to COVID-19 were included. Eleven patients (36%) received CP in combination with antiviral and supportive treatment, whereas nineteen patients (64%) in the control group only received antiviral and supportive treatment. On admission, the median age, demographic and clinical data and initial laboratory test results were similar between the groups (P > 0.05). On the 14th day of treatment, the laboratory values remained similar between the groups (P > 0.05). The mortality rates were not significantly different between the groups. CONCLUSION: CP treatment did not affect mortality or lead to clinical improvement for COVID-19 patients with ARDS.


INTRODUCTION
At the end of 2019, a novel coronavirus was recognized as a cause of viral pneumonia cases in Wuhan, China. Since it had high genetic similarity to severe acute respiratory syndrome coronavirus (SARS-CoV), the virus was officially named SARS-CoV-2 and the disease was named coronavirus disease 2019 (COVID-19). 1 The disease spread in a short time and was declared to be a pandemic by the World Health Organization (WHO) on March 11, 2020. 2 Globally, there have been 119,603,761 confirmed cases of COVID-19, including 2,649,722 deaths, reported to WHO, starting from the day on which it was first identified. 3 Currently, there is no proven effective treatment for COVID-19. 4 Convalescent plasma (CP) treatment is one of the passive immunotherapy methods used. This is a very old procedure. 5 It was used successfully against SARS-CoV in 2003, the influenza A pandemic (H1N1) in 2009, Middle East respiratory syndrome coronavirus in 2012, and Ebola virus in 2015. Mair-Jenkins reviewed the experiences from all of these epidemics and reported that CP therapy was associated with reduced mortality. 6 The use of CP for treating COVID-19 is highly controversial. 7 Ye et al. administered CP to six patients infected with SARS-CoV-2 and reported a rapid and dramatic improvement in patients who presented lung infiltration. 8 It was also reported that CP improved two patients with acute respiratory distress syndrome (ARDS) due to COVID-19. 9 In a systematic review, CP was shown to have reduced the mortality rate among highrisk COVID-19 patients. 10 On the other hand, in another study, a meta-analysis comparing CP therapy with placebo did not demonstrate any evidence of benefit from use of CP compared with placebo or standard care, with regard to clinical improvement or reduction of all-cause mortality. 11

OBJECTIVE
In this present study, we aimed to evaluate the effectiveness of CP for patients with ARDS due to COVID-19. Patients who had a diagnosis of cancer, were receiving any immunosuppressive therapy or had serum IgA deficiency, and pregnant women, were excluded from the study.

Institutional protocol for treating COVID-19 patients
For COVID-19 patients who did not need hospitalization or had mild symptoms, oral hydroxychloroquine and oral azithromycin were prioritized. All critically ill patients were treated with favipiravir. ABO-compatible plasma was used for patients from eligible donors or if the blood type-compatible plasma was already available in the blood center of the hospital. Supportive therapy consisted of oxygen and fluid supplements, and also vasopressor agents if necessary. All patients received favipiravir (1600 mg loading dose and 800 mg/day maintenance dose, orally), methylprednisolone (40-80 mg/day parenterally) and enoxaparin (4,000-6,000 IU).

Selection of CP donors
The criteria for selecting individuals as donors were as follows: I. Evidence of COVID-19 documented by a laboratory test, consisting either of a diagnostic test (e.g. on a nasopharyngeal swab) at the time of illness, or of a positive serological test for SARS-CoV-2 antibodies after recovery, if prior diagnostic testing was not performed at the time when COVID-19 was suspected; II.
Complete resolution of symptoms at least 14 days prior to donation and negative results for COVID-19 either from one or more nasopharyngeal swab specimens or from a molecular diagnostic test on a blood sample. 13 Individuals who had recovered from SARS-CoV-2 infection were invited to donate CP. All donors were informed about the apheresis procedure, and their written consent was obtained.
In addition to a RT-PCR assay for SARS-CoV-2 RNA, all potential donors were serologically screened for HBsAg, anti-HCV, anti-HIV 1-2 and anti-syphilis antibodies. The neutralizing antibody titer was not routinely obtained. The latest generation of cell separator apheresis device (Spectra Optia apheresis system; Terumo BCT, Lakewood, United States) was used to collect CP. 200-600 milliliters (ml) of plasma were collected using the apheresis device, depending on the total blood volume of the donor. Plasma components were labeled using the ISBT128 coding system and were stored below minus 18/25 °C, in storage cabinets at the blood center. No nucleic acid amplification tests or pathogen inactivation processes were routinely performed.

CP infusion
CP was delivered ready-for-use from the blood center to the pan-

Statistical analysis
The information collected was processed using the Statistical Package for Social Sciences (SPSS) for Windows, version 22.0 (IBM, Chicago, United States). The Shapiro-Wilk test was performed to check the normality assumption of the data. Parametric data were presented as mean ± standard deviation (SD), and intergroup significance was determined using Student's t test. All the analyses were performed with the significance level set at P < 0.05.

Ethics statement
The clinical research was approved by the local ethics committee (date: October 1, 2020; number: 2020/10/196). This study was conducted in conformity with the principles outlined in the Helsinki Declaration.

RESULTS
A total of 30 patients with COVID-19-related ARDS were included in this study. The mean age of the patients was 62.16 ± 9.51 years and 73% of them were male. Hypertension (43.3%) was the most common comorbid disease. Sixty percent of the patients had previously received hydroxychloroquine. Two patients (6.7%) had severe ARDS. Four patients (13.3%) needed invasive mechanical ventilation.
There was no significant difference between the groups regarding the severity of ARDS and need for respiratory support on admission (Table 1). Nasal oxygen was administered to eight patients (42%) in the control group and two patients (18%) in the CP group. On the 14 th day of treatment, the mean values ± SD of the PaO 2 /FiO 2 ratio were 227.94 ± 124.98 in the CP group and 294.34 ± 144.59 in the control group. There was no statistically significant difference between the groups (P = 0.722). The length of time taken for the CP group to be discharged from the ICU was statistically significantly longer than that of the control group.
The laboratory findings were not significantly different between the groups on the day of CP infusion (P > 0.05) ( Table 2).
On the 14 th day of treatment, the laboratory findings regarding leukocyte and lymphocyte counts and the levels of acute-phase reactants were similar between the two groups (P > 0.05) ( Table 3). One intubated patient died on the 7 th day after CP infusion. Three patients in the control group were intubated, of whom one became extubated on the 4 th day.
None of the patients developed any side effects either during or after CP infusion.

DISCUSSION
In this study, we retrospectively evaluated the effect of CP on the survival of patients with ARDS due to COVID-19 pneumonia.
We observed that CP treatment did not improve the clinical or laboratory findings. Also, it had no effect regarding improvement of survival, i.e. regarding lowering mortality. Also, the time taken to be discharged from intensive care was longer. On the 14 th day, the PaO 2 /FiO 2 ratio was lower in the CP group.

Characteristics
Discharge from the intensive care unit may have been delayed due to the longer time taken for recovery of the oxygenation level.

CONCLUSION
In our study, in which we investigated the effectiveness of CP for treating patients with ARDS due to COVID-19, we found that CP was not effective with regard to decreasing mortality.
Further prospective controlled studies are needed in order to evaluate the effectiveness of CP for treating patients with COVID-19-related ARDS.