Table 3.

Baseline characteristics of patients with type 2 diabetes on metformin monotherapy. The baseline characteristics are compared across (i) the three clinical sites and (ii) ethnicity

	(i) Clinical site			(ii) Ethnicity		Total
	Marshfield Clinic	Kaiser South East	BioVU	Caucasian	African American
Number	105	73	75	189	64	253
Male	50 (47.6%)	23 (31.5%)	37 (49.3%)	94 (49.7%)	16 (25.0%)	110 (43.5%)
Female	55 (52.4%)	50 (68.5%)	38 (50.7%)	95 (50.3%)	48 (75.0%)	143 (56.5%)
Caucasian	105	20	64	—	—	189 (74.6%)
African American	0	53	11	—	—	64 (25.4%)
Quantitative traits
Age (years)	57 ± 13	59 ± 11	57 ± 13	57 ± 13	58 ± 12	57 ± 12
BMI (kg/m2)	37.5 ± 8.6 (35.7)	38 ± 8.6 (36.1)a	32.8 ± 6.0 (31.1)b	36.0 ± 8.5 (34.2)c	35.0 ± 6.0 (34.0)d	35.9 ± 8.1 (34.2)
Baseline HbA1c (%)	7.72 ± 1.26 (7.50)	8.22 ± 1.39 (8.00)	8.32 ± 1.60 (7.90)	7.97 ± 1.42 (7.60)	8.25 ± 1.45 (8.00)	8.04 ± 1.43 (7.70)
Average metformin daily dose (mg)	901 ± 328	915 ± 454	1013 ± 472	963 ± 392	865 ± 467	938 ± 414
Creatinine clearancee (ml/min/1.73 m2)	81.2 ± 21.1	82.0 ± 17.1	NA	80.2 ± 20.1f	84.8 ± 17.7g	81.6 ± 19.5

Data shown represent mean ± SD (median).

BMI, body mass index; GFR, glomerular filtration rate; HbA_1c, glycated hemoglobin; NA, not available; Scr, serum creatinine.

^aOnly 34 people with BMI information.

^bOnly 74 people with BMI information.

^cOnly 178 people with BMI information.

^dOnly 35 people with BMI information.

^eThe following equation was used to estimate creatinine clearance from serum creatinine levels: Scr.GFR (ml/min/1.73 m²) = 175 × (Scr)^−1.154 × (Age)^−0.203 × (0.742 if female) × (1.212 if African American).⁴⁷ Weight was not required in this equation as the results are normalized to 1.73 m² body surface area, which is an accepted average adult surface area.

^fOnly 125 people with creatinine value.

^gOnly 53 people with creatinine value.