TABLE 6.

Methodology of studies investigating the association between RBP4 and IL-6¹

Study design	Study population	Sex	Age,2 y	Study size, n	Cytokine measurement method	RBP4 measurement method	Analysis	Relation	RBP4 specimen	Authors, year (ref)
In	Obese adolescents	NM	14–18	15	ELISA	Particle-enhanced immunonephlometry assay	Correlation	+	Serum	Balagopal et al., 2007 (71)
CS	Normal and impaired glucose-tolerant subjects and obese, nonobese patients with and without T2D	164 M; 69 F	48.3 ± 1.8 to 63.2 ± 3.1	233	ELISA	Gene expression	Multivariate regression	−	Adipose biopsy	Erikstrup et al., 2009 (77)
CS	Normal and impaired glucose-tolerant subjects and obese, nonobese patients with and without T2D	164 M; 69 F	48.3 ± 1.8 to 63.2 ± 3.1	233	Muscle or adipose gene expression	Gene expression	Multivariate regression	None	Adipose biopsy	Erikstrup et al., 2009 (77)
CS	Chinese	910 M; 838 F	50–70	1748	Milliplex (Millipore) human cytokine/chemokine panel	ELISA	Correlation	+	Plasma	Liu et al., 2014 (50)
CS	Healthy Swedish men	M	58	100	ELISA	Western blot	Correlation	None	Serum	Wallenius et al., 2011 (75)
Basement analysis of an intervention	Healthy men	M	19–29	65	Access immunoassay system	RIA kit	Partial correlation for age and BMI	None	Serum	Shea et al., 2007 (78)
CC	Patients with psoriasis	19 M; 11 F	48.6 ± 10.7	30	ELISA	ELISA	Correlation	−	Serum	Nakajima et al., 2013 (79)
CS	Healthy obese and overweight children	45 M; 38 F	15–8	83	ELISA	Immunonenephelometry	Multivariant regression	None	Serum	Codoñer-Franch et al., 2013 (49)
CS	Obese patients with rheumatoid arthritis	NM	NM	217	Solid-phase sandwich ELISA	Solid-phase sandwich ELISA	Mixed regression method	None	Serum	Dessein et al., 2014 (52)

¹CC, case-control; CS, cross-sectional; In, intervention; F, female; M, male; NM, not mentioned; RBP4, retinol binding protein 4; ref, reference; T2D, type 2 diabetes; +, positive; −, negative.

²Values are ranges, means ± SDs, or medians.