Among the studied group, 21 patients had PDR, 10 patients
presented NPDR, and 11 patients had normal fundi. The demographic and
laboratory characteristics of the patients are summarized in
Table 1 . The three groups of patients had similar distributions for sex, age,
body mass index, duration of DM, and systolic BP. However, patients
with PDR had diastolic BPs significantly higher than those with NPDR
and normal fundi (95 ± 13 versus 90 ± 09 and 82 ± 19
mm Hg,
P = 0.02, respectively) and were more likely to
be on antihypertensive therapy (
P = 0.001;
Table 1 ).
The metabolic control, evaluated by HbA
1c levels,
was similar in all groups of studied patients
(Table 1) . AER (geometric
mean [range]) was higher, and GFR (mean ± SD) was lower in
patients with PDR than in those with NPDR and normal fundi (333[
2–5140] versus 32 [5.9–2200] and 6 [1.5 to 306] μg/min,
P = 0.01; and 63 ± 33 versus 99 ± 37 and
93 ± 43 ml/min,
P = 0.02, respectively). The
frequency of patients with micro or macroalbuminuria was higher in
patients with PDR (80%) than in those with NPDR (40%) and normal
fundi (18%) PDR,
P = 0.001. In addition, the mean
level of the total cholesterol was significantly higher in patients
with PDR than in the other groups (6.53 ± 1.80 versus 5.10 ± 0.80 and 4.8 ± 1.2 mM,
P = 0.008).
Figure 1 shows the individual values of the erythrocyte
Na
+/Li
+ CT activity. The
mean value for Na
+/Li
+ CT
activity in patients presenting PDR was significantly higher than that
observed in patients with NPDR, normal fundi, or control group
(0.46 ± 0.20 versus 0.32 ± 0.12, 0.32 ± 11, and
0.21 ± 0.07 mM/L RBC/h, respectively,
P ±
0.0001). This difference in
Na
+/Li
+ CT activity
remained significant even when the micro and macroalbuminuric patients
were excluded from the calculation (0.55 ± 0.29 versus 0.32 ± 0.09 and 0.34 ± 0.12 mM RBC/h,
P < 0.05 for
patients with PDR,
n = 4; NPDR,
n = 6;
and normal fundi,
n = 9; respectively), suggesting that
the difference in mean
Na
+/Li
+ CT activity cannot
be accounted for solely by this group of patients. The presence of
laser therapy had no effect on
Na
+/Li
+ CT because the
activity of this cation transport was similar in patients with PDR that
had laser therapy (
n = 8) and those without laser
therapy (
n = 13; 0.48 ± 0.21 versus 0.42 ±
0.20 mM/L RBC/h,
P = 0.60). The
Na
+/Li
+ CT activity was
above the upper limit of normal (>0.38 mM RBC/h) in 12 of 21 patients
with PDR (58%), in 2 of 10 patients with NPDR (20%), and in 2 of 11
patients with normal fundi (18%;
P = 0.03).
To determine the relationship between PDR and other variables (serum
creatinine, AER, GFR, cholesterol, BP, and
Na
+/Li
+ CT activity) in the
univariate analyses, binary logistic regression models were used while
controlling for multiple potential cofounders. Subsequently, a multiple
logistic regression analysis was carried out, with PDR as the dependent
variable. In this model,
Na
+/Li
+ CT (odds ratio[
OR]: 4.7, confidence interval [CI]: 1.2–17.6;
P =
0.02), diastolic BP (OR, 3.4; CI, 1.3–9.6;
P = 0.018)
and glomerular filtration rate (OR, 5.1; CI, 1.6–17.7;
P = 0.007) were the variables that were maintained in
the equation, indicating that they were the main determinants of the
presence of PDR
(Table 2) .