Circulating VEGF as a biological marker in patients with
rheumatoid arthritis? Preanalytical and biological variability in healthy
persons and in patients
Affiliations: Department of Rheumatology, Copenhagen University
Hospital, Hvidovre, Denmark | Department of Surgical Gastroenterology, Copenhagen
University Hospital, Hvidovre, Denmark | Rheumatism Hospital, University of Southern Denmark,
Gråsten, Denmark | Department of Rheumatology, Copenhagen University
Hospital, Herlev, Denmark | Department of Clinical Immunology, Nykøbing Falster
Hospital, Denmark
Note: [] Corresponding author: Merete Lund Hetland, MD, PHD, Department
of Rheumatology 232, Copenhagen University Hospital at Hvidovre, Kettegaard
Alle 30, DK-2650 Hvidovre, Denmark. Tel.: +45 36322277; Fax: +45 36471410;
E-mail: merete.hetland@dadlnet.dk
Abstract: Background: Soluble vascular endothelial growth factor (VEGF) is a
promising biomarker in monitoring rheumatoid arthritis (RA), but studies of
pre-analytical and biologic variability are few. Methods: VEGF was
measured by ELISA methods in serum and plasma from healthy persons and RA
patients. Pre-analytical factors were investigated. A reference interval for
VEGF was established in serum and plasma from 306 healthy persons. Diurnal,
day-to-day, week-to-week, long-term variability, and impact of exercise were
evaluated. Results: Delayed processing time, room temperature, low
centrifugal force and contamination of plasma with cellular elements lead to
significant increases in VEGF levels, whereas storage for up to 2 years at
−80°C or up to 10 freeze/thaw cycles did not affect VEGF levels.
Serum VEGF levels were 7–10 fold higher than plasma VEGF levels. Reference
intervals for VEGF (plasma: 45 pg/ml (range: non-detectable to 352); serum:
328 pg/ml (53–1791)) were independent of gender and age. Short- and long-term
biologic variability included diurnal variation (sampling should take place
after 7 AM) and impact of exercise (increased VEGF immediately after bicycling
normalised within 1 hour). Conclusions: Pre-analytical factors and
biologic variability including diurnal variation and impact of exercise should
be accounted for in future studies that include circulating VEGF as a
biological marker.
