Table 2. The retinol amount measured in plasma versus its amount in DBS and the correlation coefficient between these two methods.

Method	Retinol (mmol/l)	Correlation with plasma
Plasma (n=21)	1.71±0.34 (1)	-
DBS (n=21)	1.63±0.35	0.78 (2)

⁽¹⁾Mean ± SD

⁽²⁾P = 0.00003