TIME-DEPENDENT VARIABILITY OF D-DIMER LEVEL IN BLOOD SAMPLE OF COVID POSITIVE PATIENT

Background: Coronavirus disease 2019 (COVID-19) has emerged as a global health crisis, causing significant morbidity and mortality. Beyond its respiratory manifestations, it has profound systemic effects, particularly on the cardiovascular system, where it predisposes patients to hypercoagulability and disseminated intravascular coagulation (DIC). D-dimer, a fibrin degradation product, is widely used as a biomarker to assess thrombotic activity and disease progression. Establishing whether storage time influences D-dimer values is essential for ensuring laboratory accuracy and reliability, especially under strained healthcare conditions. Objective: This study aimed to evaluate the effect of short-term storage time on D-dimer levels in samples from COVID-19–positive patients compared with healthy controls. Methods: A case–control study was conducted at Hayatabad Medical Complex, Peshawar, between June and August 2021. A total of 100 participants were enrolled, including 50 confirmed COVID-19–positive patients and 50 healthy controls. Venous blood samples (2 mL) were collected in sodium citrate tubes from the antecubital vein of each participant and analyzed using a Cobas c501 analyzer. Samples were tested immediately (0 hours), after 4 hours, and after 8 hours at room temperature. Patients with comorbidities were excluded. Paired sample t-tests were applied to assess time-related differences in D-dimer values, and Pearson correlation was used to explore associations between time and D-dimer levels. Results: In COVID-19–positive patients, the mean baseline D-dimer level was 3.77 ± 3.71 µg/mL FEU, increasing slightly to 3.81 ± 3.73 at 4 hours and 4.00 ± 3.80 at 8 hours. The corresponding two-tailed p-values were 0.366 and 0.174, both above the 0.05 threshold, indicating no statistically significant variation over time. Controls maintained consistently low D-dimer levels (0.69 ± 0.40 at baseline, 0.68 ± 0.39 at 4 hours, and 0.70 ± 0.39 at 8 hours) with p-values of 0.159. Pearson correlation revealed a weak, clinically negligible association between time and D-dimer levels. Conclusion: D-dimer values in COVID-19–positive samples remained stable over 8 hours of storage at room temperature, confirming that short-term delays in analysis do not compromise test accuracy. This stability enhances the practical utility of D-dimer testing in clinical laboratories, particularly during peak workloads in pandemics.