Study selection
A total of 3403 articles were identified through the initial literature search. After eliminating duplicates and removing Abstracts, Books & Documents, those not open access, and those not in English, 1039 articles remained. Through screening the titles and abstracts, 22 full texts were assessed for eligibility and retrieved for thorough review, excluding 13 literature reviews and 3 systematic reviews and meta-analyses. Finally, 6 studies with 382 participants were included and analyzed in this systematic review, including four randomised controlled trials, one prospective cohort study, and one retrospective case-control study. The whole process of study selection is summarized and presented in Fig. 1.
Characteristics of studies
The characteristics of studies are presented in Table 2. Four of the six included trials published in 2021 used a randomized controlled design, and the other two published in 2020 used a prospective cohort design and a retrospective case-control design respectively. All included trials were conducted in different cities in China. Among the six included studies, the number of participants in each study ranged from 11 to 157 and the mean age ranged from 46 to 60 years old. The dosage of the CHI given varied ranging between 20–200 ml per day. The duration of CHI administration spanned from 7–14 days. Only one study excluded the participants diagnosed with severe or critical COVID-19, limiting their clinical status to mild and moderate, while the clinical status of COVID-19 patients in other studies ranged from mild to critical, and two studies included only patients with severe or critical COVID-19.
Quality assessment
The risk of bias of the RCTs and non-randomized trials is shown in Fig. 2. The risk of bias in three of the RCTs were graded as “some concerns” mainly due to being open-label studies that introduced bias in deviations from intended interventions, and one RCT had an overall low risk of bias. All RCTs demonstrated a low risk of bias regarding the randomization process, missing outcome data, measurement of outcomes, and selection of the reported result. In terms of non-randomized trials, they were judged to be biased in different domains, including confounding bias, participants selection, intervention classification, and deviation from the intended intervention. One study had serious risk of bias due to confounding, but most of the other domains were at low risk, so the overall risk of bias was graded as moderate.
The quality of evidence of the included studies was assessed by the GRADE system and the results are presented in Table 3. One of the six studies was excluded from the GRADE assessment due to the lack of much of the information needed in the assessment. The evidence was of low quality for four studies, and of very low quality for one study. The factors reducing the evidence quality including limitations and imprecision contributed to the low or very low quality of evidence in these studies. There was no factor that can improve the evidence quality identified in any of the five studies.
Table 2
The characteristics of the included studies.
Study
(year)
|
Design
|
Location
|
Total sample size (mean age)
|
Clinical status of participants
|
Treatment group
|
Control group
|
Main conclusion
|
Zhang et al.
(2021)
[9]
|
A prospective, multicentre, open-label and randomized controlled trial
|
Jiangxi Province, China
|
n = 65
(46 years)
|
Diagnosed
(mild and moderate)
|
XYP injection combined with standard care
|
Standard symptomatic treatments (supplemental oxygen therapy, antiviral medicines, antibiotic agents and immune modulators)
|
XYP is safe and effective in improving the recovery of patients with mild to moderate COVID-19.
|
Xu et al.
(2021)
[8]
|
A randomized, open-labeled, multicenter clinical study
|
China
|
n = 157
(50 years)
|
Diagnosed
(mild to severe)
|
RDN injection combined with routine treatment
|
Routine treatment (supportive (oxygen), antiviral, and symptomatic treatments)
|
RDN might be effective and safe in patients with symptomatic COVID-19.
|
Luo et al.
(2021)
[5]
|
A prospective, single-center, double-blinded, randomized controlled trial
|
Hubei province, China
|
n = 57
(60 and 56 years in treatment and control group, respectively)
|
Diagnosed
(severe)
|
XBJ injection combined with routine medication
|
Routine medication (nutritional support, oxygen therapy, antiviral therapy) plus saline
|
XBJ may support possible therapeutic effects although 28-day mortality was not significantly reduced.
|
Ma et al.
(2021)
[13]
|
A randomized, open-labeled, multicenter, controlled trial
|
Lianyungang, Nanjing and Yichang, China
|
n = 50
(51 years)
|
Diagnosed
(mild except for one severe)
|
RDN injection combined with routine treatment
|
Routine treatment (supportive (oxygen), antiviral, and symptomatic treatments)
|
RDN relieves clinical symptoms in patients with COVID-19 and reduces SARS-CoV-2 infection by regulating inflammatory cytokine-related disorders.
|
Table 2
Study
(year)
|
Design
|
Location
|
Total sample size (mean age)
|
Clinical status of participants
|
Treatment group
|
Control group
|
Main conclusion
|
Ma et al.
(2020)
[21]
|
A prospective cohort study
|
Guangdong Province, China
|
n = 11
(56 years)
|
Diagnosed
(severe and critical)
|
XBJ injection
|
N/A
|
XBJ may improve lung injury in patients with severe or critical COVID-19. Moreover, XBJ could significantly protect cells from SARS-CoV-2-induced cell death and inhibit the average size and plaque number in vitro.
|
Guo et al.
(2020)
[22]
|
A retrospective case-control study
|
Chongqing, China
|
n = 42
(53 years)
|
Diagnosed
(mild and severe)
|
XBJ injection combined with routine treatment
|
Routine treatment (electrolyte balance, blood glucose and blood pressure management, nutritional support, oxygen therapy, and antiviral treatment)
|
Routine treatment combined with XBJ can better improve the clinical outcomes of COVID-19 patients.
|
COVID-19: coronavirus disease 2019; RDN: Reduning; XBJ: Xuebijing; XYP: Xiyanping.
Table 3
The quality of evidence of the included studies assessed by the GRADE system.
Studies
|
Limitations
|
Inconsistency
|
Indirectness
|
Imprecision
|
Publication bias
|
Quality of
evidence
|
Zhang et al., 2021 [9]
|
-1
|
0
|
0
|
-1
|
0
|
Low
|
Xu et al., 2021 [8]
|
-2
|
0
|
0
|
-1
|
0
|
Very low
|
Luo et al., 2021 [5]
|
-1
|
0
|
0
|
-1
|
0
|
Low
|
Ma et al., 2021 [13]
|
-1
|
0
|
0
|
-1
|
0
|
Low
|
Guo et al., 2020 [22]
|
-1
|
0
|
0
|
-1
|
0
|
Low
|
Very low: overall score < -2; Low: overall score = -2; Moderate: overall score = -1; High: overall score = 0 |
Efficacy assessment
Mortality
The cases of death were reported in three of the included studies [5, 8, 13]. Xu et al. [8] and Ma et al. [13] both reported that there were three deaths in the control group and none in the RDN group (P > 0.05). During the early stages of the study by Luo et al. [5], one patient in the XBJ group, alongside two patients in the control group, died within a week and was therefore considered drop-out cases; the results also showed the higher 28-day mortality in the control group than in the XBJ group, although the difference was not statistically significant (7 [25%] vs. 1 [3.45%], P = 0.557). There were no deaths in the other included studies.
Clinical Symptoms
The clinical symptom resolution rate or time to resolution of the clinical symptoms, including fever, cough, shortness of breath, and fatigue, was reported in five studies [5, 8, 9, 13, 22]. They all showed that the treatment group had a higher symptom resolution rate or a shorter time to resolution of the symptoms than the control group. Zhang et al. [9] found a significantly shorter meantime to complete resolution of both fever and cough in the XYP treatment group than in the control group (8.33 days [SD, 4.87] vs. 11.86 days [SD, 6.93], P = 0.006). For the RDN injection, Xu et al. [8] and Ma et al. (2021) both reported a shorter median time to resolution of the clinical symptoms in the treatment group compared to that in the control group (143 vs. 313.5 h, P < 0.001; 120 vs. 220 h, P < 0.0001), as well as the higher symptom resolution rate at 14 days and 7 days, respectively (84.4% vs. 60.0%, P = 0.0004; 96.30% vs. 39.13%, P < 0.0001). In addition, a shorter duration of primary symptoms in the XBJ treatment group than that in the control group was reported in the study by Luo et al. [5] (P < 0.05), and the number of patients who had a fever after treatment in the XBJ group was significantly lower than that in the control group in the study by Guo et al. (2020) (1 [6.25%] vs. 10 [62.5%], P = 0.002). In the study by Ma et al. [21], the pneumonia severity indexes (PSI) before and after XBJ treatment were reported, and the results showed the significantly better PSI grade and score at day 7 than those at day 1 (P < 0.05), suggesting XBJ injection could be effective in reducing the severity of COVID-19.
In terms of clinical deterioration, Zhang et al. [9] reported that there was no patient who developed severe symptoms during the trial in XYP treatment group, and six patients (9.2%) in the control group showed disease deterioration (P = 0.014). Luo et al. [5] also showed that the percentage of patients in the XBJ group who developed a critical illness during the 14 days was lower than that in the control group (10.3% [3/29] vs. 35.7% [10/28], P = 0.032).
Length of hospital stay
The length of hospital stay was reported in four studies [5, 8, 13, 22]. The significantly shorter hospital stay was observed in the RDN group compared with that in the control group in the study by Xu et al. [8] (14.1 vs. 18.1 days, P < 0.001) and the study by Ma et al. [13] (14.8 vs. 18.5 days, P = 0.0002). Additionally, Luo et al. [5] showed that the XBJ group had a significantly shorter intensive care unit (ICU) stay than the control group (8.42 days [SD, 2.26] vs. 10.72 days [SD, 3.64], P = 0.004). On the contrary, Guo et al. [22] found a slightly longer hospital stay in the XBJ group than in the control group (18.4 days [SD, 8.8] vs. 15.1 days [SD, 4.6], P = 0.348).
Although the study by Ma et al. [21] did not report the specific length of hospital stay for each patient, it showed that on day 7 after receiving XBJ treatment, all patients with severe or critical COVID-19 had been healed and discharged from the hospital.
Time taken for a negative nucleic acid test
The time taken to achieve a negative nucleic acid test result was reported in four studies [8, 9, 13, 22]. The XYP group had a significantly shorter time of nucleic acid conversion to negative than the control group in the study by Zhang et al. [9] (7.97 days [SD, 4.08] vs. 12.23 days [SD, 5.77], P < 0.001). As for RDN injection, a shorter median time to achieve a negative nucleic acid test was observed in the treatment group compared with the control group in the study by Xu et al. [8] (146.5 vs. 255.5 h, P < 0.001), as well as the study by Ma et al. [13] (215 vs. 310 h, P = 0.0017). Additionally, Guo et al. [22] found a shorter time for a negative nucleic acid test in the XBJ group compared with that in the control group, although not significantly (10.3 days [SD, 4.5] vs. 13.1 days [SD, 4.5], P = 0.183).
Blood and cell experiments
The results of blood and cell experiments were reported in four studies [5, 13, 21, 22]. There was no significant difference in leukocyte count between the treatment group and the control group (P > 0.05) [5, 21, 22]. The XBJ injections significantly improved the lymphocyte count compared with the controls (P < 0.05) [5, 21], while the the level of C-reactive protein (CRP) was significantly reduced (XBJ: 6.23 vs. control: 16.73, P < 0.01) [5]. In terms of SARS-CoV-2-induced pro-inflammatory cytokines, including IL-2, IL-6, IL-8, IL-10, TNF-𝛼, TNF-α, MCP-1, MIP-1β, IP-10, CCL-5, IFN-γ, and IFN-α, the levels of them were all significantly reduced by XBJ or RDN injections (P < 0.05) [5, 13, 21, 22].
In addition, the studies [13, 21] conducting the plaque formation assays found that RDN and XBJ injections both significantly reduce the average size and number of plaques in the treatment group compared with the control group in a dose-dependent manner. Furthermore, the cytotoxicity assay and cytopathic effect (CPE) inhibition assay were also performed in the studies [13, 21]. In the cytotoxicity assay, the TC50 value for RDN [13] and XBJ [21] in African green monkey kidney epithelial (Vero E6) cells was 168.2 and 470.7 mg/mL, respectively, and the TC50 value for RDN and XBJ in Human hepatocellular carcinoma cell lines (Huh-7) cells was 30.77 and 78.78 mg/mL, respectively. The CPE inhibition assay showed that the IC50 value of RDN [13] and XBJ [21] was 16.19 and 11.75 mg/mL, respectively, and the selectivity index (SI) of RDN and XBJ was 10.39 and 40.06, respectively.
Adverse events
The adverse events were reported in five studies [5, 8, 9, 13, 21]. In these studies, the incidence of adverse events did not differ significantly between the treatment and control groups (P > 0.05), suggesting that the adverse events were not related to the injections. Zhang et al. [9] showed that the adverse events were observed in 55 patients (84.6%) and 53 patients (81.5%) in the XYP treatment and control group, respectively. The adverse events included 1) abnormal laboratory findings, such as lymphocytopenia, neutrophilia, and increased C-reactive protein level, and 2) other common adverse events, such as chest pain, diarrhea, and nausea, most of which were mild and self-limiting. For the RDN injection, the incidence of adverse events was similar between the two groups in the study by Xu et al. [8] (RDN: 3.9% vs. control: 8.8%, P = 0.383) and study by Ma et al. [13] (RDN: 0.0% vs. control: 5.0%, P = 0.2065), and no allergic reactions or anaphylactic shocks were observed in the both studies. Similarly, there was no significant difference in the occurrence of adverse reactions between the XBJ group and control group (P > 0.05) [5, 21].