THU0441 DIAGNOSTIC ACCURACY OF THE NIJMENGEN SCORE FOR GOUTY ARTHRITIS IN PATIENTS HOSPITALIZED FOR ACUTE MONOARTHRITIS

Abstract

Background:The gold-standard for diagnosis of gout is the identification of monosodium urate (MSU) crystal in joint fluid. However, the sensitivity, specificity, and reproducibility of such analysis are not excellent, and joint aspiration is sometimes difficult, or impossible. The Nijmengen score is an easy-to-use rule without joint fluid analysis with excellent validity, in primary as well as in secondary care (1, 2). However, it’s validity as not been evaluated in the particular situation of patients whose acute arthritis necessitates hospitalization.Objectives:The objective of the present study was to assess diagnosis performances of the score in patients hospitalized for acute monoarthritis.Methods:Inclusion: all patients hospitalized for acute monoarthritis in the rheumatology department of the Dijon University Hospital between 2016 and 2019.Assessment: 1- clinical examination by an experimented rheumatologist; 2- joint aspiration and synovial fluid analysis following aspiration; 3- ultrasound (US) examination of the knees, first metatarso-phalangeal joints, and arthritic joint by a trained rheumatologist; 4- dual-energy computed tomography (DECT) of the arthritic joint; 5- Nijmengen score (cutoff scores of ≥ 8 needed for diagnosis of gout, and ≤ 4 to rule out gout) and ACR/EULAR 2015 classification criteria (3) (cut-off score of ≥ 8 needed for diagnosis of gout).Analysis: positive and negative predictive values, and ROC curve analysis of the Nijmengen score, using as gold-standard on one hand the results of the MSU crystal research, on the other hand those of the ACR/EULAR criteria.Results:A total of 39 patients were included (mean age = 69.8 ± 15 years, 74.4 % males, mean BMI = 27.5 ± 4.6 Kg/m2, mean serum uric acid = 354.6 ± 117.5 µmol/l). The affected joints were the knee (n = 31), ankle (n = 3), hip (n = 2), wrist (n = 2), shoulder (n = 1). Joint fluid analysis revealed MSU crystal in 11 patients. The ACR/EULAR was ≥ 8 in 15 patients. The Nijmengen score was ≥ 8 in 11 patients, including 5 with MSU crystal on joint fluid analysis and 9 with an ACR/EULAR score ≥ 8. The Nijmengen score was ≤ 4 in 15 patients, including 14 with no MSU crystal on joint fluid analysis and 14 with an ACR/EULAR score < 8. The positive predictive values of a Nijmengen score ≥ 8 were 45 % (joint fluid analysis as gold standard) and 81.8 % (ACR/EULAR). The negative predictive values of a Nijmengen score ≤ 4 were 93.3 % (joint fluid analysis and ACR/EULAR as gold standard). On ROC curve analyses, the areas under the curve were 0.763 (95% CI = 0.612 – 0.914) using joint fluid analysis as gold standard (figure 1) and 0.908 (95% CI = 0.814 – 1.0) using the ACR/EULAR score as gold standard (figure 2).Fig. 1ROC curve (fluid analysis as gold standard)Fig. 2Roc curve (ACR/EULAR as gold standard)Conclusion:Although having been developed for use in primary-care, the Nijmengen score appears to be useful in patients hospitalized for acute monoarthritis in a rheumatology unit.