Objectives:
Are asymptomatic patients a potential source of transmission of COVID-19?

Study design:
This review article included 506 patients from 34 studies (68 single cases and 438 from case series).

Results and conclusions:   
The investigators found patients with normal radiology were younger (19.59 ± 17.17 years) than patients with abnormal radiology (39.14 ± 26.70 years) [p value = 0.013].

Objectives:
What are common laboratory parameters for coronavirus disease 2019 (COVID-19) case detection?

Study design:
This review article included 26 studies.

Heterogeneity was considerably high in all parameters measured (I2 = between 67 and 90%).

Objectives:
Numerous studies have reported that patients with cancer seem to be more likely to be diagnosed with COVID-19. However, it is still unknown the prevalence of different types of cancer in patients with COVID-19. Therefore, this review article has been conducted.

Which types of cancer are more susceptible to COVID-19 infection?

Study design:
This review article included 6 studies, including 205 patients.

Objectives:
Does coenzyme Q10 supplementation reduce body weight and body mass index (BMI) of patients in randomized controlled clinical trial studies (RCTs)?

Study design:
This review article included 17 RCTs.

Results and conclusions:

Objectives:
Vitamin D (vitD) deficiency is a global childhood health problem. Food fortification is a promising strategy to curb vitamin D deficiency. Therefore, this review article has been conducted.

Does vitamin D fortification reduce vitamin D deficiency in healthy children aged 1-18 years?

Study design:
This review article included 20 parallel RCTs (n = 4,044), including 15 parallel RCTs and 5 cluster RCTs.
All RCTs, except for three, had a low risk of bias.

Objectives:
What is the efficacy and safety of umifenovir in COVID-19?

Study design:
This review article included 12 studies with 1,052 patients.

Results and conclusions:   
The investigators found compared with control group, umifenovir was associated with higher negative rate of PCR on day 14 [RR = 1.27, 95% CI = 1.04 to 1.5].
The results of sensitivity analysis and subgroup analysis were similar to pooled results.

Objectives:
The emergence of coronavirus disease 2019 (COVID-19) has led to high demand for intensive care services worldwide. However, the mortality of patients admitted to the Intensive Care Unit (ICU) with COVID-19 is unclear. Therefore, this review article has been conducted.

Objectives:
Nitric oxide related ergogenic aids such as arginine (Arg) have shown to impact positively on sport performance through several physiological and metabolic mechanisms. However, research results have shown to be controversial. Therefore, this review article has been conducted.

Do both acute and chronic arginine supplementation increase aerobic (≤VO2max) and anaerobic (>VO2max) performance?

Study design:
This review article included 15 RCTs with 386 males and 8 females.

Objectives:
Obesity and COVID-19 are both world epidemics now. There may be some potential relationships between them, but we knew little. Therefore, this review article has been conducted.

Does obesity increase severe COVID-19?

Study design:
This review article included 9 studies.

Results and conclusions:   
The investigators found severe COVID-19 patients had higher BMI than non-severe ones [WMD = 2.67, 95% CI = 1.52 to 3.82].

Objectives:
Is pre-existing diabetes associated with greater risk of severe/critical illness and in-hospital mortality in patients admitted to hospital with COVID-19?

Study design:
This review article included a total of 83 eligible studies with 78,874 hospitalized adult patients with laboratory-confirmed COVID-19 (52.1% men; median age 54 years [inter-quartile range: 49-62 years]).

Funnel plots and Egger's tests did not reveal any significant publication bias.