Assessment of vitamin K deficiency in CF--how much sophistication is useful?

Due to maldigestion of dietary lipids, fat soluble vitamins are prone to malabsorption in cystic fibrosis (CF) patients with pancreatic insufficiency (PICF). Routine supplementation of vitamin K(1) in PICF is presently subject of discussion.

Serum vitamin K, prothrombin time, PIVKA-II ('liver marker', by two different ELISAs), hydroxyapatite binding capacity (HBC, 'bone marker') and ApoE genotypes were measured in 32 PICF patients (age: 7 months to 25 years) with (PICFK) or without (PICFN) oral vitamin K(1) supplementation, all receiving lipase supplementation, and in 18 healthy controls (C).

PIVKA-II was positive only in 4/7 PICFN. HBC medians of all groups were 57-60%. HBC values of PIVKA-II positive patients were below HBC median of their group. There was no correlation between HBC and PIVKA-II. There was no correlation between prothrombin time and other measurements. HBC medians with regard to ApoE were ApoE2/3 (62.9%)>ApoE3/3 (57.6%)>ApoE3/4+ApoE4/4=(56.65%).

Vitamin K deficiency of liver or bone may occur independently. Prothrombin time is an insensitive marker. Individuals with ApoE4 allels might be more susceptible to osteopenia. As high expenditures are necessary to detect patients at risk, routine vitamin K supplementation for all PICF patients appears appropriate.