Assessment of disease activity in rheumatoid arthritis using a novel folate targeted radiopharmaceutical Folatescan.
OBJECTIVE
Development of a simple and accurate technique for detecting active inflammation in the joints and other tissues of patients with inflammatory disorders is an unmet need in rheumatic diseases. This study is a preliminary assessment of the safety and usage of a radiopharmaceutical, FolateScan (Technetium-99m EC20; 99mTc-EC20), for detecting disease activity in patients with rheumatoid arthritis.


METHODS
EC20 is a folate-targeted diagnostic radiopharmaceutical which binds to the folate receptor and is preferentially taken up by activated macrophages. In this open-label, cross-sectional study, a total of 40 patients with RA (26 with one or more swollen joints, 14 with clinically quiescent joint disease; 0/66 joint count) as well as 6 patients with osteoarthritis, 12 patients with other inflammatory conditions and 5 healthy subjects received 0.1 mg of EC20 labeled with 20-25mCi of technetium-99m. Disease activity was scored in each joint and other target tissues by a radiologist blinded to the clinical assessment, and results were compared to the rheumatologist's physical examination, which served as the test standard.


RESULTS
The 40 patients (78% female) with RA had a mean age of 56.9 years. Assessment of uptake of 99mTc-EC20 in joints of patients with RA based on image analysis was compared to the clinical examination. FolateScan detected more actively involved joints in 27 patients (68%) than joints recorded as "swollen", and more actively involved joints in 25 patients (63%) than joints recorded as "painful and/or swollen". The number of swollen joints by clinical exam was correlated with ESR (r=0.43; p=0.006) and C-rp (r=0.35; p=0.03). The number of actively involved joints by FolateScan was also correlated with ESR (r=0.47; p=0.002) and C-rp (r=0.36; p=0.02). Joint uptake was also seen in patients with osteoarthritis.


CONCLUSIONS
FolateScan is a potentially useful tool for detection of disease activity in patients with RA and may be more sensitive than the physical examination.
Matteson
E L
EL
Division of Rheumatology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
Lowe
V J
VJ
Prendergast
F G
FG
Crowson
C S
CS
Moder
K G
KG
Morgenstern
D E
DE
Messmann
R A
RA
Low
P S
PS
D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000000981:diagnostic imaging* / Q000473:pathology; D016022:Case-Control Studies; D005260:Female; D005492:Folic Acid / Q000031:analogs & derivatives*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009842:Oligopeptides; D010003:Osteoarthritis / Q000000981:diagnostic imaging / Q000473:pathology; D011237:Predictive Value of Tests; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D012720:Severity of Illness Index; D013670:Sodium Pertechnetate Tc 99m
C473829:EC20 folate peptide; D009842:Oligopeptides; D019275:Radiopharmaceuticals; D005492:Folic Acid; D013670:Sodium Pertechnetate Tc 99m