Study of vitamin D status of rheumatoid arthritis patients Rationale and design of a cross-sectional study by the osteoporosis and metabolic bone diseases study group of the Italian Society of Rheumatology (SIR)

摘要

The fundamental role of Vitamin D has been long known in regulating calcium homeostasis and bone metabolism. An increased contribution of Vitamin D was recently described in association with a lower incidence of Rheumatoid Arthritis (RA). This must not be surprising, as the immunomodulating effects of Vitamin D are clear, which have been attributed protective effects in autoimmune disorders such as some chronic inflammatory bowel diseases, multiple sclerosis and type I diabetes. An interaction was suggested between Vitamin D metabolism and inflammation indexes through mediation of TNF-a which is also especially involved in osteoclastic resorption and therefore in bone loss processes. Some preliminary data would indicate an association between seasonal changes of Vitamin D serum levels, latitude and disease activity (DAS28) in RA patients. Consequently, the Osteoporosis and Metabolic Bone Diseases Study Group of SIR believes that there are grounded reasons for assessing the Vitamin D status of RA patients in order to investigate whether this is to be related to physiopathological and clinical aspects of disease other than those of bone involvement. Primary end point of the study will be to assess the levels of 25 OH Vitamin D in RA patients. Secondary endpoints will include correlation with disease activity, densitometry values and bone turnover. The cross-sectional study will enrol patients of both sex genders, age ranging between 30 and 75 years according to the 1988 ACR criteria, onset of symptoms at least 2 years prior to study enrollment. Patients will be excluded suffering from osteometabolic diseases, liver and kidney insufficiency and those administered Vitamin D boli in the previous 12 months. Disease activity will be evaluated with the HAQ. Haematochemical tests and femoral and lumbar bone densitometry will be performed, unless recently undergone by patients. Blood levels of 25 OH C Vitamin D and PHT and of the two bone remodeling markers (bone alkaline phosphatase and serum CTX) will be measured, as well. Patient enrolment will start on February 2007 and will last 4 months. By the end of 2007 the study will be concluded and results will be published.