Presence of subclinical giant cell arteritis in patients with morning stiffness of duration less than 45 minutes at the time of diagnosis of polymyalgia rheumatica

Introduction: In some patients with polymyalgia rheumatica (PMR), giant cell arteritis (GCA) is subclinical as underlying inflammation of large vessels (LV) is present without evidence of related clinical manifestations. Different factors have been proposed as predictive of subclinical GCA in PMR patients. To date, the literature reports scant data about the association between subclinical GCA and long-lasting morning stiffness (MS) in patients at the time of diagnosis of PMR. Given this background, the aim of this study was to assess the association between subclinical GCA and MS < 45 min in patients with newly diagnosed PMR. Material and methods: We performed an observational, retrospective, single-centre cohort study of patients consecutively referred to our public out-of-hospital rheumatologic clinic between January 2015 and December 2020, who could be classified as having PMR according to the 2012 EULAR/ACR criteria. Subclinical GCA was investigated through ultrasound examination of a core set of arteries (temporal, axillary, common carotid, and subclavian arteries), in accordance with the EULAR recommendations for the use of imaging in LV vasculitis. Patients who did not have GCA symptoms but showed halo sign in at least one of these arteries were described as having subclinical GCA. Results: We included a total of 143 patients (35 men and 108 women). Their median age was of 71.5 years. Thirty-five had MS duration < 45 min at the time of PMR diagnosis. Subclinical GCA was found in 23 PMR patients (16.1%); 18 had a cranial and 5 an extracranial GCA. A univariate analysis highlighted that MS < 45 min was associated with a lower prevalence of GCA (OR = 0.11, 95% CI: 0.04-0.29; p < 0.0001). This association was retained in a multivariable analysis that accounted for 6 different potential covariates (OR = 0.06, 95% CI: 0.01-0.26; p < 0.0001. Conclusions: In our study MS < 45 min at the time of PMR diagnosis was associated with a significantly lower risk of subclinical GCA, when patients were screened by ultrasound, of approximately 90%. Identification of a more accurate MS cut-off value could improve the accuracy for subclinical GCA in patients with newly diagnosed PMR.