Letter to the editor about the article entitled "Proportion and mortality of Iranian diabetes mellitus, chronic kidney disease, hypertension and cardiovascular disease patients with COVID-19: a meta-analysis".

Mirjalili et al. carried out a meta-analysis to estimate the proportion and mortality of SARS-COV-2 infection among Iranian patients with diabetes mellitus (DM), chronic kidney disease (CKD), hypertension, and cardiovascular disease (CVDs) [1]. We read the study with great interest as they are still unclear what proportion of Iranian hospitalized patients with COVID-19 had the comorbidities mentioned above and to which extent these patients are at a higher risk of death [2]. They have compared the odds of death occurring in patients without comorbidity (DM, CVD, etc.) to the odds of it occurring in patients with them; so, the calculated odds ratios show the protective effect of not having DM, CVD, (all OR < 1). However, the interpretation of odds ratios is focused on the risk factor role of the assessed comorbidities throughout the text. This easily can confuse the readers. Also, on close inspection of the raw data used to generate the pooled estimates, we noticed some critical errors in data extracted from the Rastad et al. study [2], one of the largest included studies that could influence conclusions. Specifically: a) Their meta-analysis failed to calculate the prevalence of mortality and odds ratio (OR) and confidence interval in the original article. b) The corresponding sample sizes for diabetic patients deviate from the numbers reported in the original publication. The correct published values for the total number of patients with DM was 267 of whom, 48 died. c) However, the original article reported data for the patients with CVDs, but their meta-analysis failed to report them.