Complete blood count, coagulation biomarkers, and lung function 6 months after critical COVID-19

Background: Understanding the recovery of post-COVID-19 organ dysfunction is essential. We evaluated coagulation 6 months post-COVID-19, examining its recovery and association with lung function.

Methods: Patients treated for COVID-19 at intensive care units between 3/2020 and 1/2021 were analyzed for complete blood count (CBC) and coagulation biomarkers (prothrombin time activity (%) (PT%), activated partial thromboplastin time (APTT), fibrinogen, coagulation factor VIII (FVIII), antithrombin (AT), and D-dimer) during the 6 months post-hospitalization. Results were compared with acute phase values and correlated with pulmonary function tests (PFT), including forced vital capacity (FVC) and hemoglobin-corrected diffusing capacity percentage of predicted (DLCOc%), recorded 6 months post-hospitalization. We examined the association between coagulation biomarkers and DLCOc% using linear regression with age, sex, and invasive mechanical ventilation (IMV) duration, and FVIII (correlated with DLCOc%) as covariates.

Results: Most CBCs and coagulation biomarkers had median values within the normal range. However, only 21% (15/70) of patients achieved full normalization of all biomarkers. Compared to acute COVID-19, hemoglobin, PT%, and AT increased, while leukocytes, fibrinogen, FVIII, and D-dimer decreased. Despite decreased levels, FVIII remained elevated in 46% (31/68), leukocytes in 26% (18/70), and D-dimer in 27% (18/67) at 6 months. A weak negative correlation (r = -0.37, p = .036) was found between DLCOc% and FVIII. Multivariable analysis revealed a weak, independent association between DLCOc% and FVIII. Excluding patients with anticoagulation therapy, FVIII no longer correlated with DLCOc%, while AT showed a moderate correlation with DLCOc%.

Conclusion: Only a few patients had normal CBC and coagulation biomarker values 6 months after critical COVID-19. A weak negative correlation between DLCOc% and FVIII suggests that deranged coagulation activity may be associated with reduced diffusing capacity.