[Vitamin K deficiency in patients with CF despite supplementation]

Cystic fibrosis (CF) patients are at high risk for vitamin K deficiency. Vitamin K supplementation dose has not been clearly defined, and the effects of the supplementation are very ambiguous. Therefore, the aim of the present study was to assess body resources of vitamin K and determine the suitability of the coagulation parameters in the assessment of vitamin K deficiency in patients undergoing supplementation.

The study comprised 30 CF patients aged from 1.5 to 32 years. In all patients, the concentration of the undercarboxylated prothrombin (prothrombin induced by vitamin K deficiency--PIVKA-II), as a marker of vitamin K deficiency, was estimated. For comparison of the diagnostic value of existing methods of assessment of vitamin K status, the coagulation parameters were evaluated (prothrombin ratio and INR).

In spite of applied supplementation vitamin K status was not normal in all CF patients. Increased PIVKA-II concentrations (3.3-97 ng/ml) were found in 8 out of 30 (26.7%) patients, when the cut-off value of 2 ng/ml was used. Abnormal PIVKA-II levels corresponded to pathological values of the coagulation parameters only in one patient. In the remaining 7 CF subjects with increased concentration of the undercarboxylated prothrombin, coagulation parameters were normal.

Vitamin K deficiency occurs in CF patients despite applied supplementation. The accurate supplementation dose should be estimated individually and the assessment of its effectiveness requires studies allowing to determine the real body resources of vitamin K. The coagulation parameters are not a good indicator of vitamin K deficiency.