Predictive Ability of Visit-to-Visit Variability of HbA1c Measurements for the Development of Diabetic Kidney Disease: A Retrospective Longitudinal Observational Study

Table 2

Association of the risk of microalbuminuria with visit-to-visit variability of HbA1c, measured as 4 indices using a Cox proportional hazards model.

Index	HR (95% CI)^a	value^b	value^c	PS-matched subjects
				HR (95% CI)	value^b
HbA1c-SD
Q1	1	—	—	1	—
Q2	1.60 (1.11-2.30)	0.011	0.012
Q3	1.52 (1.00-2.30)	0.050	0.076
Q4	1.77 (1.12-2.79)	0.014	0.015	3.18 (1.06-9.58)	0.040
HbA1c-CV
Q1	1	—	—	1	—
Q2	1.51 (1.06-2.17)	0.024	0.022
Q3	1.19 (0.79-1.77)	0.404	0.407
Q4	1.61 (1.06-2.44)	0.026	0.025	1.54 (0.57-4.17)	0.391
HbA1c-AUC
Q1	1	—	—	1	—
Q2	1.28 (0.89-1.85)	0.183	0.158
Q3	1.51 (1.01-2.26)	0.047	0.027
Q4	1.60 (1.02-2.49)	0.039	0.032	3.29 (1.13-9.61)	0.027
HbA1c-HVS
Q1	1	—	—	1	—
Q2	1.52 (1.07-2.17)	0.019	0.018
Q3	1.19 (0.82-1.72)	0.365	0.371
Q4	1.33 (0.83-2.12)	0.235	0.258	4.23 (1.51-11.85)	0.006

The quartiles of each index are represented by Q1, Q2, Q3, and Q4. The lower quartile is denoted as Q1, and the upper quartile is denoted as Q4. ^aAdjusted by age, sex, mean HbA1c over the 3-year period, duration of diabetes, SBP, LDL-C, and presence of ischemic heart disease and heart failure at baseline. ^bAnalyzed using a Cox proportional hazards model. ^cAnalyzed using a bootstrap analysis based on 1,000 replicated datasets. HR: hazard ratio; CI: confidence interval; PS: propensity score; HbA1c-SD: internal standard deviation of HbA1c; HbA1c-CV: coefficient of variation of HbA1c; HbA1c-AUC: area under the HbA1c curve; HbA1c-HVS: HbA1c change score; SBP: systolic blood pressure; LDL-C: low-density lipoprotein cholesterol.