Table 2 .

Correlates of increased frequency of HbA_1c testing

	Excessive HbA1c testing			Frequent HbA1c testing
	Odds ratio (95% CI)	P		Odds ratio (95% CI)	P
Patient age (years)
18-44	Ref	Ref		Ref	Ref
45-54	0.94 (0.85 to 1.05)	0.29		0.97 (0.93 to 1.02)	0.23
55-64	1.08 (0.98, 1.19)	0.10		1.07 (1.03 to 1.12)	<0.001
65-74	1.17 (1.03 to 1.32)	0.01		1.12 (1.06 to 1.19)	<0.001
≥75	1.10 (0.95 to 1.27)	0.21		1.07 (1.00 to 1.15)	0.05
Sex
Male	Ref	Ref		Ref	Ref
Female	0.95 (0.89 to 1.02)	0.13		0.98 (0.96 to 1.01)	0.22
Race
White	Ref	Ref		Ref	Ref
Non-white	0.99 (0.93 to 1.04)	0.64		0.99 (0.97 to 1.01)	0.40
US census region
South	Ref	Ref		Ref	Ref
Midwest	0.67 (0.58 to 0.79)	<0.001		0.95 (0.90 to 1.01)	0.12
Northeast	1.60 (1.44 to 1.78)	<0.001		1.14 (1.08 to 1.19)	<0.001
West	1.01 (0.86 to 1.18)	0.93		0.90 (0.84 to 0.97)	0.004
Year of index HbA1c test
2001-02	Ref	Ref		Ref	Ref
2003-04	0.95 (0.78 to 1.16)	0.61		0.93 (0.85 to 1.01)	0.09
2005-06	0.97 (0.83 to 1.14)	0.73		0.86 (0.80 to 0.92)	<0.001
2007-08	1.11 (0.99 to 1.24)	0.08		1.10 (1.05 to 1.16)	<0.001
2009-10	0.74 (0.67 to 0.83)	<0.001		0.85 (0.80 to 0.89)	<0.001
2011	0.54 (0.46 to 0.64)	<0.001		0.77 (0.72 to 0.83)	<0.001
Index HbA1c
≤5.6%	Ref	Ref		Ref	Ref
5.7-6.4%	0.95 (0.88 to 1.03)	0.19		1.02 (0.99 to 1.06)	0.22
6.5-6.9%	1.29 (1.18 to 1.41)	<0.001		1.31 (1.26 to 1.37)	<0.001
Charlson comorbidity index
0-1	Ref	Ref		Ref	Ref
2	0.97 (0.87 to 1.09)	0.65		0.98 (0.93 to 1.03)	0.43
3	0.99 (0.88 to 1.10)	0.82		1.03 (0.98 to 1.09)	0.23
≥4	1.44 (1.29 to 1.61)	<0.001		1.15 (1.08 to 1.22)	<0.001
Laboratory studies obtained on the same day
HbA1c with or without glucose	Ref	Ref		Ref	Ref
Bundled tests	0.82 (0.77 to 0.88)	<0.001		0.93 (0.90 to 0.95)	<0.001
Baseline treatment
Lifestyle	Ref	Ref		Ref	Ref
1 drug	0.95 (0.87 to 1.03)	0.21		0.95 (0.92 to 0.99)	0.02
2 drugs	1.05 (0.95 to 1.16)	0.38		1.08 (1.03 to 1.14)	<0.001
≥3 drugs	1.61 (1.41 to 1.85)	<0.001		1.39 (1.29 to 1.49)	<0.001
Treatment change
No change	Ref	Ref		Ref	Ref
Deintensification	0.78 (0.65 to 0.93)	0.004		0.80 (0.73 to 0.88)	<0.001
Intensification	1.24 (1.03 to 1.49)	0.02		1.09 (0.98 to 1.20)	0.12
Drug class change only	1.53 (1.04 to 2.25)	0.03		1.32 (1.05 to 1.67)	0.02
No of healthcare providers per year	1.14 (1.10 to 1.18)	<0.001		1.05 (1.04 to 1.07)	<0.001
Coordination of care
Primary care only	Ref	Ref		Ref	Ref
Primary care and specialist care	0.73 (0.60 to 0.87)	<0.001		1.02 (0.91 to 1.15)	0.72
Specialist care only	0.70 (0.55 to 0.90)	0.006		0.77 (0.67 to 0.90)	<0.001
None	3.24 (2.01 to 5.24)	<0.001		1.31 (0.94 to 1.81)	0.11
Specialties seen
Endocrinology	1.87 (1.75 to 2.00)	<0.001		1.34 (1.29 to 1.40)	<0.001
Cardiology	1.04 (0.98 to 1.11)	0.19		1.03 (1.00 to 1.06)	0.06
Ophthalmology	1.06 (0.99 to 1.14)	0.09		1.07 (1.03 to 1.10)	<0.001
Gynecology	1.03 (0.95 to 1.12)	0.41		1.05 (1.02 to 1.09)	0.006
Nephrology	1.36 (1.23 to 1.52)	<0.001		1.09 (1.02 to 1.16)	0.008

Data are odds ratios and 95% confidence intervals (CI) of excessive and frequent testing, versus guideline recommended testing.

Ref=reference group.