Intravitreal vascular endothelial growth factor.
OBJECTIVE
To evaluate whether a specific pre-analytical stabilization regimen is needed for naïve vitreous taps to detect true values of intrinsic VEGF levels.


METHODS
Fourteen consecutive patients with different vitreomacular pathologies without blood-retina-barrier breakdown were scheduled for standard 23-gauge three-port pars plana vitrectomy, and naïve vitreous taps were sampled at the beginning of each procedure. The extracted vitreous specimen was split; one half was immediately stored in a -20 °C freezer (unstabilized samples) and the other half was instantly stabilized with albumin (2.5 % final conc.), followed by arginine stabilization (1.25 M final conc.) and consecutively stored in a -20 °C freezer (stabilized samples).


RESULTS
Intravitreal VEGF was detected in all 14 analyzed samples (100 %). VEGF levels were shown to be 46.5 pg/ml  ±  62.3 pg/ml (MV ± SD; range: 5.99-232.3 pg/ml) in unstabilized, and 120.4 pg/ml ± 94.4 pg/ml (range: 42.9 pg/ml-289.6 pg/ml) in stabilized vitreous samples. Intravitreal VEGF levels in stabilized vitreous samples were on average 2.6-fold, and thus significantly higher than in unstabilized taps of same eyes (p = 0.001, Wilcoxon test). VEGF levels in stabilized vitreous samples can be up to 8.5 times higher than in corresponding unstabilized vitreous taps of same eyes (bootstrap analysis). Intravitreal VEGF levels in unstabilized samples correlate with those in stabilized vitreous taps (r = 0.594; p = 0.025; Pearson).


CONCLUSIONS
An adequate pre-analytic stabilization regimen is needed to evaluate the most accurate intravitreal VEGF levels. This in turn will result in a better understanding of the physiological as well as pathological role of VEGF within the eye. Furthermore, knowing the true value of intravitreal VEGF levels will help to calculate the dosage of intravitrealy applied anti-VEGF drugs.
Department of Ophthalmology, Philipps-University Marburg, Baldingerstraße, 35043, Marburg, Germany, thomas.bertelmann@staff.uni-marburg.de.
Thomas
T
Bertelmann
Stephan
S
Schulze
Reka
R
Bölöni
Walter
W
Sekundo
Sebastian
S
Irle
Thomas
T
Stief
Stefan
S
Mennel
D000368:Aged; D000369:Aged, 80 and over; D001813:Blood-Retinal Barrier / Q000502:physiology; D004355:Drug Stability; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013048:Specimen Handling; D042461:Vascular Endothelial Growth Factor A / Q000032:analysis*; D014821:Vitrectomy; D057586:Vitreoretinal Surgery; D014822:Vitreous Body / Q000737:chemistry*
C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A