Fluorescence optical imaging (FOI) is useful as an additional diagnostic tool in pediatric rheumatology cases and has demonstrated signal enhancements in a majority of patients without known inflammatory joint disease, according to the results of a recent observational study published in Arthritis Research & Therapy.

A total of 76 patients with complaints of joint pain from 3 pediatric rheumatology centers in Berlin, Germany, were recruited for this study. Study inclusion criteria comprised joint pain (from existing juvenile idiopathic arthritis [JIA] or without a known reason), age 6 to 18 years, and agreement of patient and parents. FOI, gray-scale ultrasonography (GSUS), and power Doppler ultrasonography (PDUS) were performed of both hands of all patients.

Patients were divided into 3 groups: 29 patients with JIA and clinically relevant active arthritis in the hand region at the time of examination (group I); 23 patients with arthralgia (group II); and 53 patients with JIA regardless of disease activity and whether their hand region was affected at the time of examination (group III; note this group included all patients from group I). Pathologic findings were identified in 206 (24%) joints via clinical examination, 281 (32%) joints via GSUS, 118 (14%) joints via PDUS, and 395 (45%) joints via FOI.


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Joint inflammation was graded by a semiquantitative score (grades 0 to 3) for each of the imaging methods used. Joints were classified as clinically active if swollen or tender with limited range of motion. Sensitivity and specificity of FOI in 3 phases (P1 to P3) dependent on indocyanin green enhancement (PI to P3) were evaluated using CE and GSUS/PDUS as reference points. P1 was defined as the interval between the start of the examination and increased signal intensity noted in the fingertips; P2 was defined as the period of persistent increased signal intensity in the fingertips; and P3 was defined as the absence of signal intensity in the fingertips through to the end of the examination.

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In patients with JIA, FOI demonstrated overall sensitivity of 67.3% (vs GSUS) and 72.0% (vs PDUS) and specificity of 65.0% (vs GSUS) and 58.8% (vs PDUS). Specificity was highest in the P3 phase (GSUS: 94.3%; PDUS: 91.7%). FOI was more sensitive than GSUS and PDUS for detecting clinically active joints (75.2% vs 57.3%/32.5%, respectively). In patients with noninflammatory joint diseases, FOI and US demonstrated findings suggestive of inflammatory activity in 25% and 14% of joints, respectively. The predictive value for discriminating  between inflammatory and noninflammatory joint diseases was 0.79 with FOI and 0.80/0.85 with GSUS/PDUS.

The investigators concluded that based on the phase assessed, the use of FOI demonstrated moderate to good agreement with clinical examination and US. Findings identified by FOI and US should be interpreted with caution in this population, however, as limitations have been detected with each imaging modality. Additional studies in pediatric rheumatology are warranted in order to further evaluate the benefits of FOI.

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Reference

Beck MC, Glimm A-M, Ohrndorf S, et al. Fluorescence optical imaging in pediatric patients with inflammatory and non-inflammatory joint diseases: a comparative study with ultrasonography. Arthritis Res Ther. 2017;19(1):233.