Objective: To measure directly plasma vitamin K1 in patients with primary biliary cirrhosis (PBC) and to examine the relationship between vitamin K1 level, prothrombin time, other fat-soluble vitamin levels, and severity of cholestasis.
Methods: We directly measured levels of vitamin K1 (phylloquinone) in the plasma of 77 patients with PBC using reverse-phase high-performance liquid chromatography, along with serum levels of vitamins A, E, and 25-OH vitamin D.
Results: Median plasma vitamin K1 level was significantly lower in PBC patients compared with 255 normal subjects (0.65 nmol/L; range, 0.05-4.13, vs 0.95 nmol/L; range, 0.2-4.92; p < 0.0001). Of 77 PBC patients, 18 (23%) patients had levels below the normal range for plasma vitamin K1 (<0.3 nmol/L). Only 1 of the 18 patients with decreased vitamin K1 had a prolonged prothrombin time. There was no correlation between vitamin K1 level and prothrombin time in the PBC patients (p = 0.75); there was also no difference in prothrombin time between PBC patients with low vitamin K1 level and PBC patients with normal vitamin K1 level (10.3 vs 10.0 seconds; p = 0.28). PBC patients with decreased vitamin K1 levels had significantly lower vitamin A and vitamin E levels, and significantly higher serum bilirubin levels than those with normal vitamin K1 levels.
Conclusion: Decreased plasma vitamin K1 level is common in PBC, and is associated with decreased serum levels of vitamins A and E. However, the majority of PBC patients with decreased plasma vitamin K1 levels have normal prothrombin times. Although the prothrombin time is an insensitive marker of vitamin K1 status in PBC patients, clinically important vitamin K deficiency seems uncommon.