Background/Purpose: Among the arsenal of available techniques for arthritis prediction and diagnosis, fluorescence optical imaging (FOI) has shown to be useful in detecting clinically manifest and silent synovitis of the hands of patients with various rheumatic diseases. Using a probabilistic approach, we now assess the diagnostic utility of FOI in individuals that are at increased risk of inflammatory arthritis (RA in particular).

Methods: Those suspected of inflammatory arthritis were referred to the rheumatology unit and clinic of the Karolinska University Hospital. On acquiring informed consent and medical history, the standard clinical examination coupled with ultrasound findings of the hands 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 the probability resulted, then 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 (67% female, 11 RF (+), 10 ACPA (+), with age average and symptom duration (SD) of 56 (±18) years and 14 (±15) months respectively). The final diagnosis 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 the diagnostic certainty was maximal – namely, combining < 20% (lowest probability) or >80% (highest probability) of diagnostic likelihood – there was an increase from 52% (n=11/21) maximal certainty before FOI to 80% (n=17/21) maximal certainty after FOI (p=0.035). Regarding early RA, the maximal diagnostic certainty increased from 57% (n=12/21) to 71% (n=15/21) (p=0.002), respectively. The availability of ultrasound findings confirm the FOI effect. Therefore, in the event that the FOI diagnostic certainty scores did not 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 (87% (13/15) p=0.007; 85% (11/13). p=0.022, respectively).

Conclusion: Fluorescence optical imaging 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 fluorescence optical imaging in probabilistic terms.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/fluorescence-optical-imaging-in-the-diagnosis-of-individuals-suspected-of-arthritis-development-a-probabilistic-approach/