Freezing adversely affects measurement of vascular endothelial growth factor levels in human aqueous samples

Figures & data

Table 1 VEGF levels in aqueous measured fresh and after storage at −80°C for 21 days

Sample no. (n = 31)	Diagnosis	Fresh VEGF levels on day 1 (pg/mL)	Frozen VEGF levels on day 21 (pg/mL)	Difference	Percentage change from day 1
1	MD	5.60	0.60	−5.01	−89.36
2	CME	6.80	5.22	−1.59	−23.34
3	MD	9.21	1.59	−7.62	−82.73
4	CME	8.41	5.47	−2.94	−34.99
5	CME	12.01	7.75	−4.26	−35.48
6	MD	2.11	2.00	−0.10	−4.94
7	MD	1.33	1.334	+0.00	+0.30
8	MD	6.26	1.73	−4.53	−72.39
9	MD	6.35	2.83	−3.52	−55.46
10	MD	7.47	2.28	−5.20	−69.54
11	CME	1.12	0.63	−0.49	−43.93
12	DME	25.40	8.17	−17.23	−67.84
13	CME	17.81	19.41	+1.61	+9.03
14	MD	2.12	2.69	+0.57	+26.79
15	MD	2.04	1.93	−0.11	−5.29
16	MD	3.06	3.53	+0.46	+15.14
17	MD	2.04	2.90	+0.86	+42.06
18	DME	3.95	3.00	−0.95	−23.96
19	MD	13.77	10.32	−3.45	−25.04
20	MD	4.20	2.93	−1.27	−30.17
21	CME	4.94	3.08	−1.86	−37.68
22	CME	17.45	23.74	+6.29	+36.07
23	CME	13.04	11.24	−1.80	−13.80
24	DME	13.42	16.04	+2.62	+19.54
25	MD	17.31	17.86	+0.55	+3.18
26	MD	4.06	4.63	+0.57	+13.94
27	CME	5.99	8.00	+2.01	+33.60
28	MD	2.52	2.51	−0.01	−0.48
29	MD	8.27	11.50	+3.23	+39.01
30	CME	4.54	3.63	−0.90	−19.93
31	MD	11.84	13.01	+1.17	+9.90

Abbreviations: MD, macular degeneration; CME, cystoid macular edema; DME, diabetic macular edema; VEGF, vascular endothelial growth factor.

Figure 1 Comparative analysis of vascular endothelial growth factor (VEGF) concentration between fresh and frozen samples.

Note: Mean values are represented by solid red circles.

Table 2 Vascular endothelial growth factor (VEGF) levels in aqueous samples measured fresh and after storage at −80°C for 21 days based on clinical diagnosis

Serial no.	Macular degeneration		Cystoid macular edema		Diabetic macular edema
	Fresh VEGF levels on day 1 (pg/mL)	Frozen VEGF levels on day 21 (pg/mL)	Fresh VEGF levels on day 1 (pg/mL)	Frozen VEGF levels on day 21 (pg/mL)	Fresh VEGF levels on day 1 (pg/mL)	Frozen VEGF levels on day 21 (pg/mL)
1	5.60	0.60	6.8	5.22	25.40	8.17
2	9.21	1.59	8.41	5.47	3.95	3.00
3	2.11	2.00	12.01	7.75	13.42	16.04
4	1.33	1.334	1.12	0.63	–	–
5	6.26	1.73	17.81	19.41	–	–
6	6.35	2.83	4.94	3.08	–	–
7	7.47	2.28	17.45	23.74	–	–
8	2.12	2.69	13.04	11.24	–	–
9	2.04	1.93	5.99	8.00	–	–
10	3.06	3.53	4.54	3.63	–	–
11	2.04	2.90	–	–	–	–
12	13.77	10.32	–	–	–	–
13	4.20	2.93	–	–	–	–
14	17.31	17.86	–	–	–	–
15	4.06	4.63	–	–	–	–
16	2.52	2.51	–	–	–	–
17	8.27	11.50	–	–	–	–
18	11.84	13.01	–	–	–	–
Col1	Col2	Col3	Col4	Col5	Col6	Col7
Mean	6.09	4.79	9.21	8.82	14.26	9.07
SD	4.55	4.90	5.64	7.41	10.75	6.57