Monitoring VEGF levels with low-volume sampling in major vision-threatening diseases: age-related macular degeneration and diabetic retinopathy
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Abstract:
The purpose of this article is to demonstrate the capacity of paper-based ELISA (P-ELISA) to monitor VEGF in patients requiring treatment for vision-threatening diseases.BACKGROUND: There is a global epidemic of diabetes mellitus. Diabetes mellitus causes a myriad of microvascular and macrovascular complications.
Diabetic retinopathy is one of the main microvascular complications. It is preventable. However the extent of diabetic retinopathy in Zimbabwe is unknown.
METHODS: This was a cross-sectional study carried out on consenting participants, = 18years old at Parirenyatwa Group of Hospitals Diabetic Clinic. Retinopathy was assessed taking retinal photographs using an iExaminer ® which is a device comprising of a Welch Allyn Pan-optic, an indirect ophthalmoscope attached to an iPhone 4 using an adapter. Retinopathy was classified as: No Retinopathy, Non-proliferative Diabetic Retinopathy and Proliferative Diabetic Retinopathy.
RESULTS: 150 study participants were recruited with a mean age of 52.6 ± 16.4 years. The prevalence of diabetic retinopathy was observed to be 38% (n = 57) with 30.7% (n = 46) having non-proliferative diabetic retinopathy and 7.3% (n = 11) with proliferative retinopathy. Significant risk factors for diabetic retinopathy were hypertension OR 2.8 (95% CI 1.23 – 6.42), p = 0.015; age O.R 1.02 (95% CI 1.00 -1.04), p = 0.048; Diet OR 4.71 (95% CI 1.80 – 12.34), p = 0.002 and Exercise OR 11.33 (95% CI 2.62 – 49.05), p =
0.001.
CONCLUSION: The prevalence of diabetic retinopathy was 38%. Diabetic retinopathy is therefore common and largely unrecognised. Regular and appropriate easy to use screening methods are highly recommended for early detection of diabetic retinopathy so as to reduce progressive visual impairment.
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Objective To investigate the relationship of serum soluble CD40L with diabetic retinopathy(DR) in patients with type 2 diabetes mellitus(DM). Methods Serum soluble CD40L level was measured by ELISA in 30 diabetic patients without diabetic retinopathy (NDR), 29 patients with background diabetic retinopathy (NPDR), 31 patients with proliferative diabetic retinopathy (PDR), and 32 normal control(NC) subjects. Results The serum soluble CD40L levels were higher in NDR,NPDR and PDR groups [(4.55±3.66), (6.65±4.24), (8.31±5.23) μg/L,P0.01] than in NC group[(2.01±1.35)μg/L]. Conclusions Sorluble CD40L level in serum is significantly increased in type 2 DM with diabetic retinopathy,which may be correlated with pathogenesis of DR.
Pathogenesis
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Diabetic retinopathy is characterised by morphological lesions related to disturbances in retinal blood flow. It has previously been shown that the early development of retinal lesions temporal to the fovea may predict the development of treatment-requiring diabetic maculopathy. The aim of this study was to map accurately the area where lesions could predict progression to vision-threatening retinopathy. The predictive value of the location of the earliest red lesions representing haemorrhages and/or microaneurysms was studied by comparing their occurrence in a group of individuals later developing vision-threatening diabetic retinopathy with that in a group matched with respect to diabetes type, age, sex and age of onset of diabetes mellitus who did not develop vision-threatening diabetic retinopathy during a similar observation period. The probability of progression to vision-threatening diabetic retinopathy was higher in a circular area temporal to the fovea, and the occurrence of the first lesions in this area was predictive of the development of vision-threatening diabetic retinopathy. The calculated peak value showed that the risk of progression was 39.5% higher than the average. There was no significant difference in the early distribution of lesions in participants later developing diabetic maculopathy or proliferative diabetic retinopathy. The location of early red lesions in diabetic retinopathy is predictive of whether or not individuals will later develop vision-threatening diabetic retinopathy. This evidence should be incorporated into risk models used to recommend control intervals in screening programmes for diabetic retinopathy.
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The incidence of moderate visual impairment and blindness due to diabetic retinopathy was studied 5 years after introducing a screening system for early detection of treatable retinopathy. Photocoagulation was performed in patients with clinically significant macular oedema, severe preproliferative, and proliferative retinopathy. Eighty‐eight percent of 470 Type 1 and 88 % of 388 Type 2 diabetic patients were still available for follow‐up. In the Type 1 group, the five‐year incidence of blindness and moderate visual impairment were 0.5 % and 1.2 %, respectively. Corresponding figures for the Type 2 diabetic patients were 0.6 % and 1.7 %, respectively. The majority of patients with loss of vision had severe retinopathy at baseline. Among those who entered the screening programme with no or mild retinopathy, loss of vision occurred in only one of the Type 1 and four of the Type 2 diabetic patients. It is concluded that the risk for visual impairment and blindness due to diabetes can be substantially reduced by using programmes for early detection of and effective treatment of diabetic retinopathy.
Visual Impairment
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Pathophysiology
Clinical Significance
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Diabetic retinopathy, mainly a disorder of retinal vessels is influenced by the duration of the disease. From a total sample of 100 patients, a significant association was observed in the duration of diabetes and prevalence of diabetic retinopathy (P-value=0.000), as well as macrovascular complications of diabetes (P-value=0.001). This implies that with increasing duration of diabetes, the chances of prevalence of its complications increases. there was a significant association observed in duration of diabetes and macrovascular complications of diabetes in the group of 44 patients with diabetic retinopathy (P-value=0.049). There are studies suggesting diabetic retinopathy as a predictor of cardiovascular mortality in individuals both type 1 and type 2 DM. A positive association was not observed between the duration of diabetes and macrovascular complications of diabetes in the remaining 56 patients with no diabetic retinopathy (P-value=0.682). This suggests that presence of diabetic retinopathy can be a predictor of macrovascular complications due to diabetes.
Macrovascular disease
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Objective To investigate the relationship of the levels of serum 8-hydroxydeoxyguanosin (8-OHdG) to diabetic retinopathy (DR) in subjects with type 2 diabetes (T2DM).Methods The patients were classified into groups according to retinopathy (no signs of diabetic retinopathy [DM],nonproliferative diabetic retinopathy [NPDR],and proliferative diabetic retinopathy [PDR]).The concentration of serum 8-OHdG were measured with enzyme-linked immunosorbent assay (ELISA) in all 49 patients with diabetes mellitus and 22 normal control subjects.The correlation between 8-OHdG and diabetic retinopathy were analyzed in all patients with T2DM.Results The concentration of serum 8-OHdG in patients with T2DM were significantly higher than those in the control subjects (Willcoxon W Test,Z =-6.70,P =0.00; Mean Rank of T2DM group and normal control subjects are 47.00 and 11.50 respectively).There was statistical difference in the levels of serum 8-OHdG in the PDR,NPDR,and DM groups (Kruskal Wallis Test,x2=59.50,P =0.00).The levels of serum 8-OHdG was much higher in the patients with PDR than that in patients with diabetes without retinopathy and with NPDR,The concentration of serum 8-OHdG was higher in the patients with NPDR than that in patients with diabetes without retinopathy.The degree of 8-OHdG was correlated with the degree of DR (Spearman correlation coefficients=0.94,P =0.00).Conclusions The elevated serum 8-OHdG may be one of probable risk factors in the diabetic retinopathy in the patients with T2DM.
Key words:
Type 2 diabetes mellitus; 8-hydroxydeoxyguanosin; Diabetic retinopathy
Rank correlation
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