Background Rheumatoid arthritis is characterized by clinically apparent inflammatory arthritis (IA). A preclinical phase has been recognized in which symptoms arise and ambulatory care utilization increases. However, information on location and timing of symptoms before IA diagnosis is still largely lacking.
Objectives The present study was undertaken to identify pathogenetic clues to the development of IA and to assist early identification of future IA patients with a focus on musculoskeletal symptoms, infections and chronic comorbidities.
Methods We conducted a nested case-control study using data from electronic medical records of general practitioners, participating in NIVEL Primary Care Database, to evaluate timing and numbers of visits for symptoms linked to above mentioned groups before a diagnosis of IA. Cases were adults who received a newly diagnosis of IA between 2012 and 2014, in total 2772. Retrospective follow-up had a median of 3.4 years (range 1–9). Controls were matched 1:2 on age, gender, general practice and retrospective duration of follow-up. We studied a total of 192 different symptoms or (chronic) diseases using the International Classification of Primary Care (ICPC-1) coding system. The frequency of primary care visits between the IA patients and controls were compared using logistic regression in different time periods before date of diagnosis. To investigate which of the individual symptoms or diseases were seen often, chisquare tests (chi2) were performed to evaluate the difference in frequency of these symptoms in the IA-patients compared to the controls.
Results The consultation rate for musculoskeletal symptoms was increased in IA patients within the last 1.5 years before diagnosis with odds ratios (ORs) of 1.8 (confidence interval; CI: 1.6–2.1, p-value<0.05), 1.4 (CI 1.2–1.6, p<0,05) and 1.3 (CI 1.1–1.5, p<0.05), respectively, at 6, 12 and 18 months before diagnosis. For infections, the consultation rate was significantly higher 6 and 18 months prior to diagnosis (OR=1.2; both CI: 1.1–1.4, p-value<0.05). Finally, for IA-related disease and other chronic diseases a significant difference was observed only 3 months before diagnosis with ORs of 1.2 (CI 1.02–1.3, p<0.05) and 1.3 (CI 1.1–1.5, p<0.05) respectively. All ORs are corrected for age and gender. Important contributors to the above mentioned significance levels were presence of shoulder complaints (16.1% in the IA-patients versus 9.6% in the controls; chi2 73.9, p<0.001), hand/finger complaints syndrome (12.2% versus 5.6%; chi2 112.5, p<0.001), carpal tunnel syndrome (5% versus 2.5%; chi2 37.1, p<0.001) and foot/toe complaints (15.2% versus 9.2%; chi2 67.0, p<0.001). Numbers of individual infections were too small to find any statistical differences between the groups.
Conclusions We found significantly increased consultation rates in general practice for musculoskeletal symptoms and infectious diseases prior to the diagnosis of IA. This diverging trend started 4–6 years before diagnosis, but becomes statistically significant around 1.5 years preceding diagnosis. IA-related comorbidities and chronic diseases also show this trend, however this did not reach significance until nearly at the IA date. Possibly, these symptoms can be used to develop methods for earlier detection of IA in general practice.
Disclosure of Interest None declared