Background/Purpose: To evaluate the distribution of enthesitis and accuracy of physical examination (PE) for the detection of enthesitis in children, using ultrasound with power Doppler (USD) as the gold standard.

Methods: We performed a prospective cross-sectional study of 30 enthesitis-related arthritis (ERA) subjects and 30 controls. The following tendon insertion sites were assessed by standardized PE with a dolorimeter and USD: common extensor on lateral humerus epicondyle, common flexor on mediaal humerus epicondyle, quadriceps at superior patella, patellar ligament at inferior patella, Achilles, and plantar fascia at calcaneus. Abnormal tendon appearance was defined as loss of fibrillar pattern, regions of hypoechogenicity, or fusiform thickening. The cortical bone insertion was assessed with power Doppler in long and transverse imaging planes, and graded as: 0, absent; 1, minimal (1 spot); 2, moderate (2 spots); 3, severe (>3 spots). Since minimal power Doppler findings have been previously identified in normal children, positive findings were defined as grade 2 or above.

Results: Median age of the ERA subjects was 13 years (IQR: 11,15). Sixty percent were male and 30% were HLA-B27+. Abnormal findings were detected most commonly by USD at the insertions of the quadriceps (30%; N= 18/60 sites), common extensor (12%; N=7/60), and Achilles (10%; N=6/60) tendons, which are different than the most common sites of enthesitis in adults with spondyloarthropathy. Fifty-seven percent (N=17/30) of ERA subjects had an abnormal USD at 1 or more entheses and 33% (N=10/30) at 2 or more entheses. Abnormal USD findings were detected in control subjects at 2% (N=1/60) of common extensor tendon insertions and at none of the remaining insertion sites. The intra-and inter-rater reliability of USD (kappa) were 0.78 (95% CI: 0.63, 0.93) and 0.81 (95% CI: 0.67, 0.95), respectively. Tenderness detected by standardized dolorimeter exam had poor positive predictive value (average, range across entheses) for USD-confirmed enthesitis. Tenderness occurred most commonly at the insertions of the patellar ligament (80%; N=48/60 sites), quadriceps (78%; N= 47/60 sites), and common extensor tendons (55%; N=33/60 sites). Eighty-seven (N=26/30) percent of subjects had tenderness at 3 or more entheses and 57% (N=17/30) at 6 or more entheses. Inter-rater reliability of dolorimeter exam for detection of enthesitis was low (kappa 0.49, 95% CI:  0.33, 0.65). In comparison to controls, ERA subjects reported more pain and had lower pain thresholds at every site, including control sites (all p-values <0.001).

Conclusion:

Tenderness detected by standardized dolorimeter exam overestimated USD-confirmed enthesitis in children with ERA. Compared to USD, PE for the detection of enthesitis in children has poor accuracy and reliability. The significantly decreased pain threshold of ERA subjects at all sites likely contributed to the limited accuracy of PE. Future research is warranted regarding the utility of USD for identifying enthesitis at JIA diagnosis, accurately predicting disease progression, and guiding therapeutic decisions.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/detection-of-enthesitis-in-children-with-enthesitis-related-arthritis-dolorimeter-examination-compared-to-ultrasonography/