Coronavirus disease 2019 (COVID-19) is the third known animal coronavirus, after 
severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome 
coronavirus (MERS-CoV). The mean age of the infected patients was estimated to 
be between 50 and 69 years old. Accordingly, the COVID-19 mortality rate was 
calculated as 15%. In this regard, the essential component of prevention and 
planning is knowledge of laboratory and demographic findings among COVID-19 
patients; therefore, the present study was conducted to investigate laboratory 
and demographic findings among these patients worldwide. This systematic review 
was performed on the articles published in English between January 1, 2019 and 
May 4, 2020, using MeSH-compliant keywords such as "COVID-19", "Laboratory, 
coronavirus disease-19 testing", and " demography " in international databases 
(PubMed, and web of science Scopus). Thereafter, the articles relevant to 
laboratory and demographic findings among COVID-19 patients were included in the 
final review. Reviewing the included articles showed changes in the mean 
lymphocytes count ranged from 0.7 to 39 in hospital or severe cases. Moreover, 
Leukopenia was not observed in patients with thrombocytopenia. In addition, 
C-reactive protein (CRP), leukocytes, D-dimer, FDP, FIB, neutrophils, AST, serum 
creatinine, t-troponin, troponin I, and blood bilirubin levels showed increasing 
trends in most studies conducted on COVID-19 patients. Notably, the elevated LDH 
level was more common among children than adults. According to the results of 
the present study, and by considering the clinical characteristics of COVID-19 
patients on the one hand, and considering the changes in laboratory samples such 
as lymphocytes and other blood markers due to the damaged myocardial, hepatic, 
and renal tissues on the other hand, it is recommended to confirm the diagnosis 
of this infection by evaluating the patients' blood samples using other 
diagnostic methods like lung scan.