PB0879 - Association between Serum Anti Platelet Factor 4, Platelet Count, D-dimer, and Vitamin D Status in Patients with Moderate COVID-19 Infection

Background: Anti Platelet Factor 4 (anti-PF4) is commonly associated with heparin-induced thrombocytopenia (HIT). However, anti-PF4 can also initiate platelet activation, which develop into thrombosis. Thrombosis has been a major complication in COVID-19, especially in severe cases. Vitamin D has anti-inflammatory properties and therefore can ameliorate thrombosis. There is limited evidence on their relationship especially in moderate COVID-19.

Aims: This study aims to determine the association between serum anti-PF4, platelet count, D-dimer, and vitamin D status in moderate COVID-19.

Methods: This is a cross-sectional study. Data was obtained from the large dataset of previous studies of vitamin D-COVID-19 and anti-PF4-COVID-19 in two national referral hospital for COVID-19 in Jakarta, Indonesia. Vitamin D was measured as 25-OH Vitamin D3 using chemiluminescence immunoassays (CLIA) method. Anti-PF4 was measured using ELISA. Data was analyzed using SPSS version 29.0.

Results: There were 58 subjects with moderate COVID-19, 43% were male. Mean age was 48.7 years old (SD: 16.28). There was moderate correlation between anti-PF4 and D-dimer (r=-0.53, p< 0.001). Anti-PF4 did not correlate with platelet count. There were significant differences between D-dimer levels of patients with sufficient versus insufficient vitamin D (p=0.002). Increased anti-PF4 and D-dimer are known to be associated with severe COVID-19. In this study, there was a negative correlation between anti-PF4 and D-dimer. The mechanism of this is still unknown, but the hypothesis is that D-dimer is not elevated in moderate disease, while anti-PF4 seems to be triggered early in the course of disease, similar to mechanism in vaccine-induced immune thrombotic thrombocytopenia (VITT), irrespective of platelet count.

Conclusion(s): Anti-PF4 did not correlate with platelet count and was inversely correlated with D-dimer, although Anti-PF4 exerts thrombogenic effect through binding with PF4 on platelets. The data also showed that vitamin D sufficiency is likely to be protective through its antiinflammatory properties. Further studies are needed to confirm these findings.