Background The diagnosis of giant cell arteritis (GCA) can only be ascertained by performing temporal artery biopsy (TAB), and there is no validated biomarker valuable for the diagnosis and/or characterization of the prognosis in this condition. Recently, Baerlecken et al. reported on the detection of antibodies directed at the human ferritin heavy chain (FTH1)in 92% of patients with GCA vs 1% of healthy controls.
Objectives We decided to evaluate the diagnostic value of anti-ferritin antibodies in patients undergoing TAB for a suspicion of GCA.
Methods We included 122 consecutive patients suspected of GCA. Blood sampling was performed at the time of TAB. Among these, 40 had biopsy proven GCA (TAB+ GCA), 29 had biopsy-negative GCA (TAB- GCA), 6 had polymyalgia rheumatica (PMR) and another diagnosis that GCA (GCA controls) and/or PMR was retained in 47 patients. Sera from 40 healthy individuals served as negative controls. We investigated for the presence of IgG directed against 19-45 FTH1 amino-acids by using an ELISA test. Correlations between FTH1 antibodies and clinical manifestations were investigated using non parametrical tests.
Results Anti-FTH1 antibodies were identified in 72.5%, 41.3.9%, 31.9% and 2.5% of patients with TAB+ GCA, TAB- GCA, GCA controls and healthy individuals, respectively, with a threshold at the mean of healthy controls + 2 standard deviations (SD). With a threshold at the mean of healthy controls + 3 SD, anti-FTH1 antibodies were identified in 60%, 34.5%, 21.2% and 0% of the patients with TAB+ GCA, TAB- GCA, GCA controls and healthy individuals, respectively.
By grouping TAB+ GCA, TAB- GCA patients with a threshold at 2 SD, the positive and negative predictive value were of 71.9 and 56.9%, respectively. Positive and negative likely ratio were at 1.96 and 0.58, respectively. In addition, in our population, anti-FTH1 antibody titer as measured by OD level correlated significantly with CRP and no correlation was found with aortic and/or visual impairment.
Conclusions We therefore confirm the presence of anti-FTH1 in 72.5% of patients with histologically proven GCA. However, the detection of anti-FTH1 is not contributory to the diagnosis of GCA in a cohort of patients with suspected ACG. The ability to identify a specific sub-group of patients by ELISA should be evaluated by testing a larger cohort of patients with GCA.
References Baerlecken et al. Ann Rheum Dis. 2012 Jun;71(6):943-7.
Disclosure of Interest None Declared