Table 1.

Selected observational trials on the incidence of vitamin D deficiency in ICU patients.

Author, Journal, Year	Design	No of patients	Vitamin D deficiency definition	Outcomes
	Population
Braun A, Critical Care Medicine, 2011Boston, Massachusetts, USA (5)	Retrospective observational studyMedical and surgical ICU patients	2399	Pre-admission 25(OH)D was categorized as deficiency in 25(OH)D (≤15 ng/mL), insufficiency (16–29 ng/mL) and sufficiency (≥30 ng/mL)	Deficiency: 27% (637 patients)Insufficiency: 38% (918 patients)Sufficiency: 35% (844 patients)
Amrein K, Critical Care, 2014Graz, Austria (13)	Retrospective observational studyMedical and surgical ICU patients	655	25(OH)D was categorized as deficiency in 25(OH)D (≤20 ng/mL), insufficiency (20–30 ng/mL), normal (>30 ng/mL)	Deficiency: 60% of patientsInsufficiency: 26% of patientsNormal level: 14% of patients
Matthews LR, American Journal of Surgery, 2012Atlanta, USA (74)	Prospective observational studySurgical ICU patients	258	25(OH)D was categorized as severe deficiency in 25(OH)D (≤13 ng/mL), moderate deficiency (14–26 ng/mL) and mild deficiency (27–39 ng/mL), sufficiency (>40 ng/mL)	Severe deficiency: 54% (138 patients)Moderate deficiency: 37% (96 patients)Mild deficiency: 7% (18 patients)Sufficiency: 1% (3 patients)
Venkatram S, Critical Care, 2011New York, USA (75)	Retrospective studyMedical ICU patients	437	25(OH)D was categorized as deficiency in 25(OH)D (0–19 ng/dL), insufficiency (20–29.9 ng/dL) and normal levels (≥30 ng/mL)	Deficiency: 78% (340 patients)Insufficiency: 17% (74 patients)Normal level: 5% (23 patients)
Higgins DM, Journal of Parenteral and Enteral Nutrition, 2012Ontario, Canada (76)	Prospective studyMedical and surgical ICU patients	196	25(OH)D was categorized as deficiency in 25(OH)D (<12 ng/mL), insufficiency (12–24 ng/mL) and normal levels (>24 ng/mL)	Deficiency: 26% (50 patients)Insufficiency: 56% (109 patients)Normal level: 19% (37 patients)
Nair P, Intensive Care Medicine, 2015Sydney, Australia (25)	Prospective multicenter cohort studyICU patients	100	25(OH)D was categorized as deficiency in 25(OH)D (<10 ng/mL), insufficiency (10–20 ng/mL) and normal levels (>20 ng/mL)	Deficiency: 21% (21 patients)Insufficiency: 55% (55 patients)Normal level: 24% (24 patients)