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Prevalence of vitamin K deficiency and associated factors in non-supplemented cystic fibrosis patients.

INTRODUCTION
Vitamin K deficiency is highly prevalent in cystic fibrosis (CF) patients despite supplementation. Moreover, no reliable risk factors for its occurrence are known. The aim was to assess the prevalence of vitamin K deficiency and associated factors in non-supplemented CF patients.


METHODS
Prothrombin concentration induced by vitamin K absence (PIVKA-II) and the undercarboxylated osteocalcin percentage (u-OC) were determined. In all patients clinical status was assessed and its relation to vitamin K deficiency determined. The following tests were used for statistical analysis: Mann-Whitney test, ANOVA test or the Kruskal Wallis test, the chi-squared test or the Fisher-Freeman-Halton test, and multiple linear and multiple forward stepwise logistic regression analysis.


RESULTS
The study group comprised 79 CF patients aged 0.4-25.3 years. PIVKA-II and u-OC were abnormal in 56 (70.9%) and 45 (57.0%) patients. Patients with elevated PIVKA-II were significantly older (p= 0.0184) and had lower Z-score values for body weight (p= 0.0297) than those with normal concentrations. Patients with normal or pathological u-OC percentage did not differ. Abnormal PIVKA-II and u-OC were reported more frequently in subjects with two severe CFTR mutations and with worse/poor nutritional status. Multiple linear and forward stepwise regression analyses did not reveal strong predictive factors of vitamin K deficiency.


CONCLUSION
Vitamin K deficiency is highly prevalent in the natural course of cystic fibrosis. There are no reliable clinical determinants of its occurrence.