Circulating VEGF as a biological marker in patients with rheumatoid arthritis? Preanalytical and biological variability in healthy persons and in patients.
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 degrees 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.
Hetland
Merete Lund
ML
Department of Rheumatology, Copenhagen University Hospital, Hvidovre, Denmark. merete.hetland@dadlnet.dk
Christensen
Ib Jarle
IJ
Lottenburger
Tine
T
Johansen
Julia Sidenius
JS
Svendsen
Mads Nordahl
MN
Hørslev-Petersen
Kim
K
Nielsen
Lone
L
Nielsen
Hans Jørgen
HJ
D000925:Anticoagulants; D001172:Arthritis, Rheumatoid / Q000097:blood*; D015415:Biomarkers / Q000097:blood*; D002940:Circadian Rhythm; D019343:Citric Acid; D015925:Cryopreservation; D004492:Edetic Acid; D004797:Enzyme-Linked Immunosorbent Assay; D015444:Exercise; D006493:Heparin; D006801:Humans; D010949:Plasma / Q000737:chemistry; D012016:Reference Values; D013048:Specimen Handling / Q000379:methods; D042461:Vascular Endothelial Growth Factor A / Q000097:blood*
D000925:Anticoagulants; D015415:Biomarkers; D042461:Vascular Endothelial Growth Factor A; D019343:Citric Acid; D006493:Heparin; D004492:Edetic Acid