ACCURACY AND PRECISION OF INTRAVITREAL INJECTIONS OF ANTI-VASCULAR ENDOTHELIAL GROWTH FACTOR AGENTS IN REAL LIFE: What Is Actually in the Syringe?

Abstract

To evaluate the accuracy and precision of anti-vascular endothelial growth factor volume delivery by intravitreal injections in the clinical setup. Volume output was measured in 669 intravitreal injections administered to patients, calculated from the difference in syringe weight before and after expelling the drug. Three groups were included: prefilled bevacizumab 1.0 mL syringe (Group 1, n = 432), pre-filled ranibizumab in a small-volume syringe with low dead-space plunger design (Group 2, n = 125), and aflibercept drawn and injected using a 1.0-mL syringe (Group 3, n = 112). Accuracy was analyzed by mean absolute percentage error, and precision by coefficient of variation. Volume outputs in all 3 groups were significantly different from the target of 50 μL (P < 0.0001 for all), and mean absolute percentage error values were 12.25% ± 5.92% in Group 1, 13.60% ± 8.75% in Group 2, and 24.69% ± 14.84% in Group 3. No difference was found between groups 1 and 2, but both were significantly more accurate than Group 3 (P < 0.0001 for both). The current practices used for intravitreal injections are highly variable, with overdelivery of the anti-vascular endothelial growth factor drugs measured in most cases, but underdelivery in 16.3% of injections. Use of a prefilled syringe was associated with improved accuracy, and low dead-space plunger design may improve precision.