3.1. Literature Search Results
For the case of MetHb and COVID-19, a total of 201 articles were initially retrieved from PubMed (n = 6) and Google Scholar (n = 196) using the literature search strategy mentioned above. Based on the inclusion and exclusion criteria, seven duplicates were removed and 187 articles were excluded after abstract review. After the full set of remaining articles was screened, seven reports were finally included in the present study [17,18,19,20,21,22,23]. The study selection process is shown in Figure 1a.
For the case of COHb and COVID-19, 73 articles were retrieved from PubMed (n = 1) and Google Scholar (n = 72), one duplicate was removed and 68 articles were excluded after abstract review, leading to three articles that were finally included in the present study [20,24,25]. The study selection process is shown in Figure 1b.