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Elad Moisseiev, Itamar Loewenstein, Michaella Goldstein, Joseph Moisseiev; Accuracy and Precision of Intravitreal Injections of Anti-VEGF Agents in Real Life. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5705. doi: https://doi.org/.
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To evaluate the accuracy and precision of anti-VEGF volume delivery by intravitreal injections in real-life clinical practice.
Volume output was measured in 669 intravitreal injections administered to patients, calculated from the difference in syringe weight before and after expelling the drug. Weight was measured using an electronic analytical balance, with a resolution of 0.1 mg. Volume output was then calculated using the specific densuty of each drug. Three groups were included: institutional pre-filled 1.0 mL syringe with bevacizumab (group 1, n=432), commercially available pre-filled small-volume syringe with low-dead-space plunger design with ranibizumab (group 2, n=125), and aflibercept drawn by the injecting physician and injected with a 1.0 mL syringe (group 3, n=112). The three groups represent different combinations of anti-VEGF agents, drawing techniques and syringes. Accuracy was analyzed by mean absolute percentage error (MAPE), and precision by coefficient of variation (CV).
Volume outputs in all three groups were significantly different from the target of 50 µL (0.05 mL) (p<0.0001 for all). MAPE 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). CV values were 0.086 in group 1, 0.096 in group 2 and 0.136 in group 3. Volume outputs larger than the target of 50 µL were measured in 83.7% of the injectons, and notably more in group 3 (96.4%) than in groups 1 and 2. A deviation of more than 10% of the intended volume delivered by the intravitreal injection was measured in 41.1% of cases.
Current practices of intravitreal injections are highly variable, with over-delivery of the anti-VEGF drugs measured in most cases. Use of a pre-filled (groups 1 and 2) syringe was associated with improved accuracy, and low-dead-space plunger design (as in group 2) may improve precision. This is the first study to evaluate the volume of intravitreal anti-VEGF agents delivery in the clinical setup, and it highlights their sub-optimal accuracy and precision. It also illustrates the need for a specially designed syringe for intravitreal injections, and suggests the optimal syringe for this purpose should be a pre-filled, small volume syringe with a low-dead-space plunger design.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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