Elevated plasma factor VIII levels in a mixed patient population on anticoagulation and past venous thrombosis.

BACKGROUND

Thrombophilia conditions are associated with an increased risk of venous thromboembolism. Elevated plasma levels of factor VIII (>150 IU/dL) increase the risk of venous thrombosis. The aim of this report is to analyze a subset of patients in whom plasma factor VIII levels were investigated as part of a thrombophilia panel at a specialty venous clinic at a tertiary care hospital.

METHODS

From January 2019 to December 2019, records of all patients (n = 306) who had a plasma factor VIII level assay performed as part of a thrombophilia panel were retrospectively analyzed. Group 1 (n = 92) had normal factor VIII levels (≤150 IU/dL), whereas group 2 (n = 214) had elevated factor VIII levels (>150 IU/dL). Venous thromboembolic events were classified as provoked if there was an association with surgery, trauma, immobilization, orthopedic fracture, peripartum period, or use of hormones. If there was no associated factor identifiable in the patient's history, the event was considered unprovoked.

RESULTS

The median age for patients in groups 1 and 2 was 55 and 65 years, respectively. Family history of deep venous thrombosis (DVT) was noted in 6 patients in group 1 (6.5%) vs 77 patients in group 2 (36%), P value: .0001. Unprovoked DVT was more commonly noted in group 2 patients (66%) compared with group 1 patients (5%), P value: .0001. In addition, venous ulceration was more commonly encountered in group 2 (23%) than group 1 (11%), P value: .008. Factor VIII level >150 IU/dL was a significant predictor of DVT occurrence itself (odds ratio: 3.3, P value <.005). Factor VIII level >200 IU/dL was a significant predictor of occurrence of two or more episodes of DVT (odds ratio: 12.3, P value < .005).

CONCLUSIONS

Factor VIII levels were found to be elevated in a significant proportion of patients in whom thrombophilia testing was performed at a specialty venous clinic. This elevation was more common in patients with venous ulceration, a positive family history of DVT, and a personal history of an unprovoked DVT. Levels above 200 IU/dL were associated with DVT recurrence. This has important implications for secondary prophylactic strategies for DVT.