A cross-sectional study comparing osteoporosis in two populations of children with and without JIA: a cross-sectional study with a control group.

Abstract

BACKGROUND: Juvenile idiopathic arthritis (JIA) is the most common rheumatic disease in children. Today, thanks to early diagnosis and the therapeutic options available to us, its comorbidities have been substantially reduced. Even so, we do not know the current incidence of some of them. Especially those that occur silently, such as low bone mineral density (BMD) for chronological age or even childhood osteoporosis(OP). OBJECTIVES: The aim of this study is to evaluate the prevalence of low BMD for chronological age/OP in patients diagnosed with JIA and in their different subtypes of JIA and to compare it with healthy paediatric patients. We also want to study the variables that may be associated with low BMD/OP in patients with JIA and define phosphocalcium analytical parameters, including vitamin D, and markers of bone turnover in these patients. DESIGN AND PARTICIPANTS: This study is designed as a cross-sectional study comparing two populations of patients with and without JIA. It is an observational and multicentre study, consisting of JIA patients followed up in the Paediatric Rheumatology Unit of 7 referral hospitals in Catalonia and their control group, consisting of the patient's relatives (siblings or cousins aged 5-16), adjusted for age, sex, weight and height, who wish to participate in the study. METHODS: 134 patients will be recruited with a consecutive non-probabilistic sample method. Recruitment of patients will last 2 years. They will be divided into two groups depending on the presence or absence of JIA. BMD in children is measured at the lumbar spine (LS) or whole body less head (WBLH) using DXA adjusted by age, sex and height by Z-score. This, together with knowledge of previous fractures, allows us to assess the presence or absence of osteoporosis