3.1. Baseline Characteristics of Participants
The study included 1230 patients with T2DM who had complete electronic medical records. The prevalence of DR was 34.88% (429/1230) and the prevalence of PDR was 8.05% (99/1230) among the T2DM patients. The mean (SD) age of the patients was 59.41 (12.85) years in Non-DR group, 60.51 (11.51) years in NPDR group, 58.74(10.70) years in PDR group, which had no difference among the three groups (P > 0.05) (Table 1).
Table 1. Characteristics of the patients with T2DM by the severity of DR (n = 1230)
|
Non-DR
(n = 801)
|
NPDR
(n = 330)
|
PDR
(n = 99)
|
P-value*
|
Age(years)
|
59.41±12.85
|
60.51±11.51
|
58.74±10.70
|
0.294
|
Male (%)
|
57.80
|
49.09
|
53.54
|
0.026
|
Duration of diabetes(years)
|
8.41±6.47
|
12.09±6.31
|
13.74±7.60
|
0.000
|
BMI (kg/m 2 )
|
24.11±3.50
|
24.96±3.43
|
25.73±8.01
|
0.806
|
HbA1c, %
|
8.76±2.32
|
9.40±2.18
|
9.95±2.25
|
0.002
|
Fasting blood glucose (mg/dl)
|
7.69±2.72
|
8.45±3.24
|
9.30±3.82
|
0.000
|
Total cholesterol (mmol/L)
|
4.12±1.19
|
4.05±1.14
|
4.54±1.44
|
0.001
|
Triglyceride (mmol/L)
|
1.78±1.44
|
1.74±1.30
|
2.14±2.29
|
0.057
|
HDL-C (mmol/L)
|
0.97±0.27
|
0.98±0.28
|
1.03±0.31
|
0.211
|
LDL-C (mmol/L)
|
2.25±0.88
|
2.18±0.84
|
2.37±0.95
|
0.140
|
Hypertension (%)
|
48.31
|
49.70
|
54.55
|
0.493
|
SCr (μmol/L)
|
68.48±24.10
|
70.58±30.72
|
80.90±36.36
|
0.000
|
BUN (mmol/L)
|
5.69±1.86
|
6.09±2.01
|
6.63±2.19
|
0.000
|
eGFR
|
121.32±34.22
|
118.25±37.72
|
102.74±36.01
|
0.000
|
MPV(fl)
|
10.26±1.18
|
10.37±1.19
|
10.55±1.10
|
0.045
|
Plt count/cm2
|
193.56±58.71
|
187.26±53.73
|
182.94±58.04
|
0.084
|
Continuous values are expressed as mean ± SD. P <0.05 is indicated in bold.
Abbreviations: Non-DR: non-diabetic retinopathy, NPDR: non-proliferative diabetic retinopathy, PDR: proliferative diabetic retinopathy; BMI, body mass index; HbA1c, glycated hemoglobin a1c; HDL-C, high-density lipoprotein cholesterol; LDL-C, low-density lipoprotein cholesterol; SCr: serum creatinine; BUN: blood urea nitrogen; eGFR, estimated glomerular filtration rate; MPV: mean platelet volume; Plt: platelets.
3.2. Changes in Systemic Parameters among different DR Groups
Univariate analysis on clinical and laboratory data of the participants was summarized in Table 1. Characteristics of patients among the three groups significantly differed in gender, duration of diabetes, HaemoglobinA1c(HbA1c), fasting plasma glucose(FPG), total cholesterol, serum creatinine(SCr), blood urea nitrogen (BUN), estimated glomerular filtration rate(eGFR) , and MPV (all P < 0.05). There was no significant difference in age, body mass index (BMI), hypertension, triglycerides, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and platelet count among the three groups (all P > 0.05).
MPV was 10.26±1.18fL in non-DR group, 10.37±1.19fL in NPDR group, and 10.55±1.10fL in PDR group. Figure 1 showed that the MPV was highest in the PDR group and the association was statistically significant (P = 0.045).
3.3. Risk Factors and prediction model of PDR
Multiple logistic regression analysis was performed to find variables having independent association with PDR (Table 2, n =1230). Compared with Non-DR, MPV showed significant relation with PDR (OR=1.304, 95% CI, 1.084-1.567). Other variables showing independent association with PDR were duration of diabetes (OR=1.118, 95% CI, 1.082-1.155), HbA1c (OR=1.142, 95% CI, 1.027-1.271), FPG (OR=1.131, 95% CI, 1.049-1.219), total cholesterol (OR=1.253, 95% CI, 1.063-1.476) and eGFR (OR=0.987, 95% CI, 0.976-0.998). Based on these variables, the prediction model of PDR was logit(P)=(-8.434)+0.112×duration of diabetes +0.133×HbA1c+0.123×FPG +0.225×total cholesterol -0.013×eGFR +0.265×MPV.
We performed the ROC analysis to assess the predictive power of the prediction model and these variables which had independent correlation with PDR on multivariate analysis. As shown in Figure 2, the prediction model provided a more excellent forecast for PDR (AUROC = 0.790) than any risk factor. Among the risk factors, duration of diabetes was the strongest predictive factor for PDR (AUROC =0.707), followed by FPG (AUROC =0.620) and HbA1c (AUROC =0.619). And meanwhile, total cholesterol and MPV provided relatively poor prediction for PDR(AUROC =0.579, 0.573).
Table 2. Multiple Logistic Regression Analysis Showing the Parameters with Significant Association with PDR (n = 1230).
|
Variable
|
B
|
Adjusted
OR
|
95% CI
|
P-value*
|
PDR
|
intercept
|
-8.434
|
|
|
|
|
Male (%)
|
0.121
|
1.128
|
0.671-1.897
|
0.649
|
|
Duration of diabetes(years)
|
0.112
|
1.118
|
1.082-1.155
|
0.000
|
|
HbA1c, %
|
0.133
|
1.142
|
1.027-1.271
|
0.015
|
|
Fasting plasma glucose (mg/dl)
|
0.123
|
1.131
|
1.049-1.219
|
0.001
|
|
Total cholesterol (mmol/L)
|
0.225
|
1.253
|
1.063-1.476
|
0.007
|
|
SCr (μmol/L)
|
0.000
|
1.000
|
0.987-1.014
|
0.978
|
|
BUN (mmol/L)
|
0.075
|
1.078
|
0.939-1.238
|
0.286
|
|
eGFR
|
-0.013
|
0.987
|
0.976-0.998
|
0.024
|
|
MPV(fl)
|
0.265
|
1.304
|
1.084-1.567
|
0.005
|
P <0.05 is indicated in bold. The prediction model of PDR was logit(P)=(-8.434)+0.112×duration of diabetes +0.133×HbA1c+0.123×random blood glucose +0.225×total cholesterol -0.013×eGFR +0.265×MPV.
Abbreviations: NPDR: non-proliferative diabetic retinopathy, PDR: proliferative diabetic retinopathy; BMI, body mass index; HbA1c, glycated hemoglobin; SCr: serum creatinine; BUN: blood urea nitrogen; eGFR, estimated glomerular filtration rate; MPV: mean platelet volume.