FRI0630 DIAGNOSTIC UTILITY OF FLUORESCENCE OPTICAL IMAGING IN INDIVIDUALS WITH SUSPECTED ARTHRITIS – A PROBABILISTIC APPROACH

Abstract

Background In the arsenal of available techniques used for arthritis prediction and diagnosis1, fluorescence optical imaging (FOI) has been proven useful in detecting clinically manifest and silent synovitis of the hands and wrists of patients with various rheumatic diseases, particularly rheumatoid arthritis (RA)2. Objectives To assess the diagnostic utility of FOI in individuals with joint symptoms referred for further rheumatologic investigation, using a probabilistic approach. Methods Those with increased suspicion of inflammatory arthritis were referred to the rheumatology unit and clinic of Karolinska University Hospital. On acquiring informed consent and medical history, the standard clinical examination coupled with ultrasound findings of fingers, wrists and feet were assessed. Laboratory results included ESR, CRP, RF, and ACPA tests. Using the above information, a diagnostic probability assessment was completed by the responsible rheumatologist, where the probability of a) any inflammatory joint disease and b) rheumatoid/RA was given on a 5-point scale – ranging from unlikely (0-20%) to very likely (80-100%) probability. Subsequently, an FOI examination was performed. After reviewing the image reports in consensus, post-FOI diagnostic probabilities were again scored, using the same scale. If no score change in probability resulted, the rheumatologist was asked to mark whether FOI was still helpful in the diagnostic decision-making. Proportions of individuals with maximal and minimal diagnostic certainty pre- and post-test were compared using Fisher exact tests, and one-sample binomial tests for assessing the helpfulness of FOI in the absence of pre- and post-test probability score changes. Results Of 24 individuals screened, 21 without prior rheumatic diagnosis were included (66.7% female, 11 RF (+), 10 ACPA (+), with age average and symptom duration (SD) of 55.6 (±18.1) years and 13.9 (±15.3) months respectively). The final diagnoses were: early RA (n=17), other inflammatory joint disease (n=3), and non-inflammatory joint disease (n=1). Regarding diagnosis of any inflammatory arthritis, where the proportion of patients for whom diagnostic certainty was maximal – namely, combining 80% (highest probability) of diagnostic likelihood – there was an increase from 52.4% (n=11/21) maximal certainty before FOI to 80.1% (17/21) maximal certainty after FOI (p=0.035). Regarding early RA, the maximal diagnostic certainty increased from 57.1% (12/21) to 71.4% (15/21) (p=0.002), respectively. In the event that diagnostic certainty scores didn’t change pre- vs. post-test (15/21 cases, any inflammatory joint disease; 13/21 cases, early RA), the diagnosing rheumatologist indicated that FOI was still helpful in setting a final diagnosis for most cases (86.7% (13/15) p=0.007; 84.6% (11/13), p=0.022, respectively). Conclusion FOI significantly increased the diagnostic certainty and confidence of rheumatologists in establishing the presence and absence of inflammation in individuals suspected of inflammatory arthritis. The changes from pre- to post-test quantify the diagnostic utility of FOI in probabilistic terms.