'Chronic inflammatory rheumatic joint diseases' is a generic term for conditions characterised by non-infectious inflammation in the joints and/or spinal column. This group of diseases includes, for example, rheumatoid arthritis, psoriatic arthritis and spondyloarthritis. Both the disease itself and treatment of the disease, which often involves immunosuppression, can entail a heightened risk of infection (1–3). After the outbreak of COVID-19, rheumatology departments have received may enquiries from patients and healthcare personnel about potential risks associated with the use of immunosuppressants and whether this patient group is considered to be at special risk. Based on national and international recommendations, our advice to patients has been to continue with their usual medication as long as they have no symptoms of an infection (4, 5). There has been limited documentation for this recommendation.
Some studies have found that patients with rheumatic diseases had a higher incidence of COVID-19 (6, 7), while others have not indicated this, including when the patients were taking conventional disease-modifying drugs (8). In one study, the use of biological or targeted synthetic disease-modifying drugs was found to be a risk factor for infection (8), while two other studies found no such association (9, 10). In many of these studies, the diagnosis is based on symptoms and exposure to infection, with no requirement for a positive laboratory test. The studies are small, and even though the number of published works is rising, it remains uncertain whether patients with chronic inflammatory rheumatic disease are at a higher risk of infection than others.
Nor is it clear whether these patients have a more serious course of the COVID-19 disease. Some studies have found a higher incidence of intensive care (11) and a need for mechanical ventilation (11, 12) in patients with rheumatic diseases. A higher risk of hospitalisation has also been found in patients with rheumatic diseases who use prednisolone in doses ≥ 10 mg on a daily basis (13). Other studies have not found any more serious courses of disease than in the general population (14, 15).
In a recently published Norwegian study, no elevated incidence of inflammatory rheumatic joint diseases was found among patients who had tested positive for SARS-CoV-2 or patients who were hospitalised for COVID-19 compared to the general population (16).
The objective of our study was to investigate the incidence of COVID-19 among patients with chronic inflammatory rheumatic joint diseases in Norway compared to that of the general population. We wished to see whether factors associated with the rheumatic disease, the patient or the medication impacted on the incidence rate. Furthermore, we wished to identify the proportion of the infected patients who needed hospitalisation and intensive care.