Respiratory failure and coagulopathy are life-threatening complications caused by COVID-19 because of a cytokine storm. Low-molecular-weight heparin (LMWH) is the most common anticoagulant used in hospitals. Apart from its potential as an anticoagulant, it also has anti-inflammatory and antiviral effects, so we believe that we can use it as a thromboprophylaxis in COVID-19 cases. Objective: To determine the relationship between the use of LMWH thromboprophylaxis on D-Dimer and the PF ratio in COVID-19 patients. Methods: This study is an observational analytic study with a retrospective cohort design carried out in the isolation room and ICU of RSUP HAM. The study subjects were ≥ 18 years old patients who were confirmed positive for COVID-19 based on RT-PCR results and received anticoagulants for seven days. We divided the study subjects into two groups, the LMWH (+) group, which received 0.5 cc/day enoxaparin subcutaneously for seven days, and the non-LMWH group who received other types of anticoagulants. We took blood samples for blood gas analysis and d-dimer test before giving the intervention, 5 and 7 days after administration. Comparative analysis of PF ratio and d-dimer levels before and after the Paired t-test analyzed the intervention. Results: 34 study subjects comprising 20 men and 14 women followed this study. The mean baseline PF ratio was lower in the LMWH (+) group and increased consistently until day 7. There were differences in the PF ratio before and after thromboprophylaxis in both groups (p = 0.022; 0.018). The baseline D-dimer level was higher in the LMWH (+) group and decreased until day 7 with a more significant reduction difference than the nonLMWH group. There was a significant difference found before and after thromboprophylaxis in both groups (p = 0.016; 0.034). Conclusion: There was a significant relationship between using LMWH thromboprophylaxis in increasing the PF ratio and reducing D-dimer levels in COVID-19 patients.

Keywords : PF Ratio, D-Dimer, Thromboprophylaxis, COVID-19.