Anticardiolipin antibody levels predict flares and relapses in patients with giant-cell (temporal) arteritis. A longitudinal study of 58 biopsy-proven cases.

OBJECTIVE: To evaluate the usefulness of anticardiolipin antibodies (aCL) in identifying flares and relapses in giant-cell arteritis.
METHODS: We studied 58 consecutive patients with biopsy-proven temporal giant-cell arteritis. C-reactive protein and aCL serum levels were measured simultaneously at the time of diagnosis and at each out-patient visit until recovery. All observed episodes of a rise in C-reactive protein attributable to a precise cause, for which the simultaneous measurement of aCL was available, were analysed.
RESULTS: The mean duration of clinical observation and serum aCL assessment was 34+/-18 and 24+/-11 months, respectively. Anticardiolipin antibody positivity (IgG or total antibodies > or =20 U) before treatment was found before treatment in 27 cases (46.6%) (mean 45.6+/-26 U/l, range 20-110 U). Levels of aCL decreased below 10 U with appropriate treatment in all patients except one, after a variable delay. No rise in aCL levels was recorded subsequently in any patient whose disease was controlled permanently. A significant rise in aCL was recorded in 20 of 27 (74%) of the flares or relapses of giant-cell arteritis, including seven of 12 flares in seven patients whose initial aCL level was <20 U vs none of the 28 inflammatory episodes unrelated to giant-cell arteritis (P<0.0000001). IgM aCL, infrequently found at diagnosis, was not associated with signs of disease activity.
CONCLUSION: Serum aCL levels are useful in the detection of flares and relapses in giant-cell arteritis, with fairly good sensitivity (74%) and a specificity of 100%, and can be of value in distinguishing subclinical flares from infection.