Correlation between glycated hemoglobin A1c, urinary microalbumin, urinary creatinine, β2 microglobulin, retinol binding protein and diabetic retinopathy

Table 1 General information of the three groups (mean ± SD)

Group	Age (yr)	Sex (M/F)	Duration of illness (yr)	Systolic blood pressure (mmHg)	Diastolic blood pressure (mmHg)
NDR (n = 68)	57.71 ± 7.18	37/31	4.21 ± 0.81	117.47 ± 19.38	76.05 ± 9.48
NPDR (n = 54)	58.00 ± 8.93	29/25	6.22 ± 1.26	118.32 ± 16.02	75.34 ± 11.91
PDR (n = 58)	56.59 ± 7.12	31/37	8.12 ± 1.47	111.33 ± 18.09	75.69 ± 7.96
F/χ2 value	0.534	0.013	169.133	2.606	0.178
P value	0.587	0.994	< 0.001	0.078	0.836

NDR: Diabetes mellitus without retinopathy; NPDR: Non-proliferative diabetic retinopathy; PDR: Proliferative diabetic retinopathy.

Table 2 Clinical indicators among the groups (mean ± SD)

Group	HbA1c (%)	FPG (mmol/L)	TC (mmol/L)	TG (mmol/L)	LDL-C (mmol/L)	HDL-C (mmol/L)
NDR (n = 68)	8.01 ± 1.86	8.60 ± 1.96	4.86 ± 0.98	1.68 ± 0.21	2.61 ± 0.42	1.15 ± 0.22
NPDR (n = 54)	9.14 ± 2.12	8.55 ± 1.94	4.42 ± 0.75	1.69 ± 0.27	2.62 ± 0.41	1.24 ± 0.20
PDR (n = 58)	10.28 ± 2.66	8.92 ± 2.16	4.55 ± 0.84	1.77 ± 0.29	2.74 ± 0.54	1.22 ± 0.27
F value	15.385	0.572	0.319	2.216	1.476	1.073
P value	< 0.001	0.565	0.726	0.112	0.231	0.344

NDR: Diabetes mellitus without retinopathy; NPDR: Non-proliferative diabetic retinopathy; PDR: Proliferative diabetic retinopathy; HbA1c: Glycated hemoglobin A1c; FBG: Fasting blood glucose; HDL-C: High-density lipoprotein cholesterol; LDL-C: Low-density lipoprotein cholesterol; TC: Total cholesterol; TG: Triglyceride.

Table 3 Comparison of microalbumin, microalbumin/urinary creatinine, urinary creatinine, β2 microglobulin and retinol binding protein levels in each group (mean ± SD)

Group	mALB (mg/L)	mALB/U-CR (mg/mmoL)	U-CR (μmol/L)	β2MG (mg/L)	RBP (μg/L)
NDR (n = 68)	15.04 ± 1.94	2.19 ± 0.86	6.86 ± 1.67	2.28 ± 0.66	12.29 ± 2.82
NPDR (n = 54)	65.69 ± 7.30	3.29 ± 1.26	19.97 ± 5.81	3.13 ± 0.84	21.58 ± 4.83
PDR (n = 58)	170.29 ± 11.63	5.09 ± 1.02	33.35 ± 11.45	4.53 ± 0.97	36.78 ± 7.84
F value	147.103	121.668	206.027	117.619	69.460
P value	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001

NDR: Diabetes mellitus without retinopathy; NPDR: Non-proliferative diabetic retinopathy; PDR: Proliferative diabetic retinopathy; U-mALB: Urinary microalbumin; U-CR: Urinary creatinine; β2MG: β2 microglobulin; RBP: Retinol binding protein.

Table 4 Multiple linear regression analysis of risk factors associated with the development of proliferative diabetic retinopathy

Independent variable	B value	SE	β value	t value	P value
Course of disease	1.203	0.293	0.220	4.106	< 0.001
HbA1c	0.942	0.192	0.755	4.906	< 0.001
mALB	0.874	0.128	0.256	6.828	< 0.001
mALB/U-CR	0.743	0.284	0.525	6.959	< 0.001
U-CR	0.842	0.121	0.254	6.959	< 0.001
β2MG	1.048	0.123	0.157	8.520	< 0.001
RBP	1.262	0.184	0.215	3.271	< 0.001

HbA1c: Glycated hemoglobin A1c; U-mALB: Urinary microalbumin; U-CR: Urinary creatinine; β2MG: β2 microglobulin; RBP: Retinol binding protein.

Table 5 Receiver operator characteristic curve analysis of glycated hemoglobin A1c, microalbumin, microalbumin /urinary creatinine, urinary creatinine, β2 microglobulin, retinol binding protein for predicting proliferative diabetic retinopathy

Item	Cut-off	Standard error	AUC	95%CI	Sensitivity (%)	Specificity (%)
mALB	56.84 mg/L	0.040	0.641	0.530-0.688	68. 82	71.24
mALB/U-CR	2.45 mg/mmoL	0.046	0.726	0.728-0.876	70.38	73.85
U-CR	25.96 μmol/L	0.004	0.757	0.508-0.722	72.49	75.58
β2MG	3.18 mg/L	0.027	0.748	0.637-0.882	76.84	79.84
RBP	26.58 μg/L	0.036	0.807	0.637-0.882	82.48	79.38
HbA1c	9.05%	0.043	0.710	0.638-0.775	72.41	63.11
Combination	-	0.017	0.958	0.917-0.982	94.83	96.72

AUC: Area under the curve; U-mALB: Urinary microalbumin; U-CR: Urinary creatinine; β2MG: β2 microglobulin; RBP: Retinol binding protein; HbA1c: Glycated hemoglobin A1c; Combination: Glycated hemoglobin A1c + microalbumin + microalbumin/urinary creatinine + urinary creatinine + β2 microglobulin + retinol binding protein.