Human Reproduction, Vol. 19, No. 1, 221,
January 2004
© 2004 European Society of Human Reproduction and Embryology
Reply: Methological concerns regarding levels of vascular endothelial growth factor (VEGF) in serum of patients with endometriosis
Metriogene BioSciences (a subsidiary of PROCREA BioSciences), Montréal, Canada, H4P 2R2
1 To whom correspondence should be addressed. e-mail: dgosselin{at}metriogene.com
Ferrero et al. questioned our approach to measure VEGF levels in serum (Gagné et al., 2003
) because it may reflect VEGF secreted by platelet degranulation during clotting, which could have been minimized by adding anticoagulant to the blood samples. However, we would like to recall that the objective of our study was chiefly to shed some light on the controversy concerning the modulation of VEGF measured in the serum of patients with endometriosis compared to controls. As clearly stated, we thus have compared our results with those of Pellicer et al. (1998) and Matalliotakis et al. (2003) who have reported apparent inconsistent results concerning VEGF serum levels in patients with endometriosis. Therefore, the study of VEGF levels in plasma samples was totally out of the scope of our study. Although the study of VEGF plasma levels could bring additional information, the interpretation of the results from such plasma samples still remains ambiguous. Indeed, this is even acknowledged in the study quoted by Ferrero et al. (Hormbrey et al., 2002), where >75% of plasma levels are below the standard range with a coefficient of variation as high as 35%. Furthermore, Hormbrey et al. (2002) have also highlighted the lack of consensus on whether platelet count, platelet size or any other parameters should be taken into account to correctly interpret plasma VEGF levels.
Also, according to Ferrero et al., our blood samples should have been processed within 1 h following collection (in contrast with 5 h, as mentionned in our study). In support of this assumption, Ferrero et al. referred to the study of Hormbrey et al. (2002), who reported a significant difference in VEGF serum levels when the samples were processed between 2 and 6 h after blood collection. However, after a careful look at the results presented in figure 4 of Hormbrey’s study, it appears that such modulations are below the 10% variation limit of the detection kit and are, thus, not biologically meaningful.
Ferrero et al. finally referred to the results of Banks et al. (1998) and mentioned that the interpersonal variation in generation of VEGF in clotted samples may make the interpretation of any observed difference between disease and control groups very difficult and may invalidate the results. The interpersonal variation reported by Banks et al. (1998) is not surprising, as their study includes only four individuals. We agree that interindividual variations exist in VEGF levels and underline the importance of studying a large number of samples in any comparative studies. We circumvented this limitation in our study by including a total of 277 individual samples, thus minimizing the impact of any possible interindividual variations in VEGF serum levels.
References
Banks RE, Forbes MA, Kinsey SE, Stanley A, Ingham E, Walters C and Selby PJ (1998) Release of the angiogenic cytokine vascular endothelial growth factor (VEGF) from platelets: significance for VEGF measurements and cancer biology. Br J Cancer 77,956–964.[Web of Science][Medline]
Gagné D, Pagé M, Robitaille G, Hugo P and Gosselin D (2003) Levels of vascular endothelial growth factor (VEGF) in serum of patients with endometriosis. Hum Reprod 18,1674–1680.
Hormbrey E, Gillespie P, Turner K, Han C, Roberts A, McGrouther D and Harris AL (2002) A critical review of vascular endothelial growth factor (VEGF) analysis in peripheral blood: is the current literature meaningful? Clin Exp Metastasis 19,651–663.[CrossRef][Web of Science][Medline]
Matalliotakis IM, Goumenou AG, Koumantakis GE, Neonaki MA, Koumantakis EE, Dionyssopoulou E, Athanassakis I and Vassiliadis S (2003) Serum concentrations of growth factors in women with and without endometriosis: the action of anti-endometriosis medicines. Int Immunopharmacol 3,81–89.[CrossRef][Web of Science][Medline]
Pellicer A, Albert C, Mercader A, Bonilla-Musoles F, Remohi J and Simón C (1998) The follicular and endocrine environment in women with endometriosis: local and systemic cytokine production. Fertil Steril 70,425–431.[CrossRef][Web of Science][Medline]
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