Table 2.

Sampling schedule

Serum concentration	Day 0 (day of enrolment)	Day 2	Day 5	Day of intensive care unit discharge
25-hydroxyvitamin D	√	–	√	√
1,25-dihydroxyvitamin D	√	√	√	√
Calcium (Ca)	√	√	√	√
Phosphate (P)	√	√	√	√
Parathyroid hormone	√	√	√	√
Fibroblast growth factor 23	√	–	√	√
Vitamin D binding protein	√	–	√	√