TABLE 1.

Selected demographics and plasma retinol concentrations in healthy young people and in subjects with SCD-HbSS before and after vitamin A supplementation¹

	Healthy (n = 20)	SCD-HbSS pre-supplementation (n = 22)	SCD-HbSS post-supplementation (n = 21)
Sex, % males	60	59	57
Age, y	14 (9–19)	14 (9–19)	14 (9–19)
Plasma retinol, μmol/L	1.47 (0.87–2.27)2	1.12 (0.46–2.35)	1.24 (0.74–2.37)

SCD-HbSS, sickle cell disease hemoglobin SS type.

¹Subjects were participants in the studies reported by Brownell et al. [6]. Tabulated values are arithmetic mean (range), except for sex, which is reported as percent males. Plasma retinol concentration was calculated as [¹²C]retinol + [¹³C]retinol. Values for the healthy group include 19 subjects at 3 d after isotope ingestion and 1 at 5 d. For the SCD-HbSS group before supplementation, values include all 22 subjects at 3 d whereas after supplementation, values are for 20 of the same subjects (with n = 14 at 3 d, 4 at 4 d, 1 at 7 d, and 1 at 8 d). Retinol concentrations were compared between healthy subjects and subjects with SCD-HbSS pre-supplementation using Student’s unpaired t test. Subjects with SCD-HbSS were compared before and after vitamin A supplementation using a mixed effects linear regression model adjusting for hydroxyurea use and including a time × dose interaction term. The Benjamini and Hochberg false discovery rate method was applied with a maximum false discovery rate of 0.05 to derive corrected P values to address the issue of multiple testing.

²Significant difference between group means using unpaired t test, P < 0.05.