Table 2.

Number of blood samples used for the assessment of serum vitamin D levels in the JIA and control groups and for each season for each geographical region included in our study.

Regions	Group	Samples ( n )
		Winter	Spring	Summer	Autumn	Total
Moscow	JIA	22	4	23	17	66
	Healthy	54	11	20	39	124
Stavropol	JIA	21	16	22	21	80
	Healthy	29	25	28	68	150
Krasnoyarsk	JIA	16	9	31	16	72
	Healthy	28	27	34	28	117
Total	JIA	59	29	76	54	218
	Healthy	111	63	82	135	391

Serum vitamin D levels were interpreted as per the 2011 recommendations of the International Society of Endocrinologists (20, 21): deficiency, calcidiol (25(OH)D) level <20 ng/mL; insufficiency, 20–29 ng/mL; and normal, 30–100 ng/mL.

JIA, juvenile idiopathic arthritis.