A recent study by Holden and co-workers in 172 subjects with stage 3–5 CKD showed that the criteria for subclinical vitamin K deficiency were met by 6 % of the patients based on circulating K1 measurements, by 60 % based on OC carboxylation and by 97 % based on PIVKA-II levels [9]. Here, KRT1 is linked to chronic kidney disease.