VEGF Suppression Times in DME Treated With Ranibizumab
VEGF Suppression Times in DME Treated With Ranibizumab
Seventeen eyes of seventeen patients were included in the study. The clinical characteristics of the study population are depicted in Table 1. We were able to acquire 110 aqueous humour samples out of a total of 123 intravitreal ranibizumab injections in all patients that were administered during the study. For each patient, we determined VEGF levels (y-axis) in relation to the time interval from the previous ranibizumab injection (x-axis) (figure 1). The first injection was defined as day 0.
(Enlarge Image)
Figure 1.
Scatter diagrams of two patients showing the time interval since the previous intravitreal ranibizumab injection and the corresponding vascular endothelial growth factor levels in aqueous humour.
Complete VEGF suppression was assumed when VEGF levels were below 4 pg/mL, near to the detection limit of the analytic method. Measurements were clustered between 30 and 40 days because monthly injections were scheduled as treatment series. Measurements with longer intervals correspond to new treatment series. For the analysis of the duration of VEGF suppression, we determined the latest time point of complete suppression. VEGF was completely suppressed below detection limit in all patients for a minimum of 27 days. We observed a mean VEGF suppression time of 33.7 days (SD±5.1, range 27–42, median 34). The distribution of individual VEGF suppression times is shown in figure 2. VEGF suppression times were individually stable: In individual patients, no measurement showed non-suppression at a time point when suppression would have been expected from other measurements in this patient. VEGF levels at baseline and before the beginning of a new injection series are shown in Table 1. There was no statistical difference between these two time points (p=1.0, Wilcoxon), and there was no correlation between VEGF levels at baseline and VEGF suppression time (rs=−0.338, p=0.201, Pearson).
(Enlarge Image)
Figure 2.
Distribution of individual vascular endothelial growth factor suppression times.
Results
Seventeen eyes of seventeen patients were included in the study. The clinical characteristics of the study population are depicted in Table 1. We were able to acquire 110 aqueous humour samples out of a total of 123 intravitreal ranibizumab injections in all patients that were administered during the study. For each patient, we determined VEGF levels (y-axis) in relation to the time interval from the previous ranibizumab injection (x-axis) (figure 1). The first injection was defined as day 0.
(Enlarge Image)
Figure 1.
Scatter diagrams of two patients showing the time interval since the previous intravitreal ranibizumab injection and the corresponding vascular endothelial growth factor levels in aqueous humour.
Complete VEGF suppression was assumed when VEGF levels were below 4 pg/mL, near to the detection limit of the analytic method. Measurements were clustered between 30 and 40 days because monthly injections were scheduled as treatment series. Measurements with longer intervals correspond to new treatment series. For the analysis of the duration of VEGF suppression, we determined the latest time point of complete suppression. VEGF was completely suppressed below detection limit in all patients for a minimum of 27 days. We observed a mean VEGF suppression time of 33.7 days (SD±5.1, range 27–42, median 34). The distribution of individual VEGF suppression times is shown in figure 2. VEGF suppression times were individually stable: In individual patients, no measurement showed non-suppression at a time point when suppression would have been expected from other measurements in this patient. VEGF levels at baseline and before the beginning of a new injection series are shown in Table 1. There was no statistical difference between these two time points (p=1.0, Wilcoxon), and there was no correlation between VEGF levels at baseline and VEGF suppression time (rs=−0.338, p=0.201, Pearson).
(Enlarge Image)
Figure 2.
Distribution of individual vascular endothelial growth factor suppression times.
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