BackgroundGiant cell arteritis (GCA) and osteoporosis (OP) share many epidemiological features, such as occurrence in people >50 years old and increased incidence in women and northern Europe. Some known risk factors of OP, such as early menopause, nulliparity, low body mass index (BMI) and smoking, have also been linked to increased risk of GCA.ObjectivesWe performed this study to investigate a potential link between OP and GCA onset by screening for OP by computed tomography (CT).MethodsWe retrospectively analyzed consecutive patients who underwent temporal artery biopsy (TAB) for suspected GCA in 4 hospitals. Cases and controls were defined by TAB-proven GCA and non-GCA diagnosis, respectively. Selection criteria additionally included 18F-FDG PET/CT at ±30 days (GCA cases) or ±90 days from the date of TAB (non-GCA controls). A radiologist blinded to patients’ case or control status used CT images to measure the mineral density of trabecular bone in the first lumbar vertebra of all patients. OP was defined by previously identified thresholds of ≤110 Hounsfield units (HU) or ≤135 HU (1). We compared cases and controls for proportion of OP for the entire population and by sex. Statistical analyses involved chi-square and Student t tests for categorical and continuous variables, respectively.ResultsWe included 50 cases and 59 controls. The most common diagnoses for controls were neurological disorders (n=21), autoimmune diseases (n=8), infections (n=10) and lack of an identifiable acute disease (n=9). Main demographic characteristics, prior cardiovascular and OP risk factors, and laboratory results are in the Table. Cases and controls did not differ in proportion with OP in the overall population (46% vs 49% [≤110 HU] and 60% vs 69% [≤135 HU]) or by sex (Table).ConclusionThis study confirms that OP risk factors, that is, low BMI and nulliparity, are overrepresented in GCA, but our data do not suggest higher OP frequency in patients with new-onset GCA than controls. The high absolute proportion of OP in patients with new-onset GCA deserves further investigation because it may have practical implications in these patients at risk of glucocorticoid-induced bone loss.Reference[1] Pickhardt PJ et coll. Opportunistic screening for osteoporosis using abdominal computed tomography scans obtained for other indications. Ann Intern Med. 2013 16;158:588-95.Disclosure of InterestsClaire LE PENDU: None declared, Patrick TCHOUANTE: None declared, Kim LY: None declared, Jean-François ALEXANDRA: None declared, Natella ASLANBEKOVA: None declared, Khadija Benali: None declared, Solange GONZALEZ-CHIAPPE: None declared, Sarah LECHTMAN: None declared, Damien Sene: None declared, Cornelia Weyand: None declared, karim sacre Grant/research support from: GSK, Alfred Mahr Consultant for: Chugai Pharma France, Speakers bureau: Roche SAS Chugai Pharma France