Background/Purpose: Reactive Arthritis (Re.A) is an inflammatory joint disease that according to different records represents from 6% to 47% of the seronegative spondyloarthropathies (SS). These differences may be due to genetic and/or environmental variations as well as the absence of an agreement on the definition of case and validated classification criteria. Objective: to assess and compare the diagnostic value of the classification criteria for Re.A in a cohort patients.

Methods: consecutive adult patients (≥18 years old) were included from 5 Argentinian centers, with Re.A diagnosed by rheumatologists with broad experience in this entity, and as a control group, patients with rheumatoid arthritis (RA), ankylosing spondylitis (AS) and psoriatic arthritis (PsA). Clinical data, laboratory and radiological characteristics employed by the different criteria were retro-prospectively collected and recorded. We classified each patient according to different classification criteria: Calin, Third International Workshop of ReA, American College of Rheumatology (ACR), European Spondylarthropathy Study Group (ESSG), Amor and Assessment of Spondyloarthritis international Society (ASAS) for peripheral arthritis, having registered their fulfillment. Statistical analysis: we described the variables under study. Sensitivity, specificity, positive and negative predictive value (PPV/NPV) and likelihood ratios (LR) for each criteria were assessed by double entry table.

Results: thirty six patients with Re.A (78% male), were included, median age (SD): 36 (12) years, median (IQR) disease duration: 22 (2-444) months. Fifty-six percent presented urethritis, 28% gastroenteritis, 8% cervicitis and 8% other infections. Forty-four, 33 and 17% had mono, oligo y polyarthritis respectively, 86% asymmetrical and 61% predominant in lower limbs. Inflammatory spinal pain and sacroiliitis were detected in 56% and 36% respectively; enthesitis 50% and dactylitis 14%. Extra-articular manifestations: uveitis 17%, conjunctivitis and balanitis 8%, keratoderma blennorrhagica and genital ulcer 3%. Radiographic features: 30% had sacroiliitis. In the control group 36 patients (16 PsA, 15 RA, 5 AS) were evaluated; they had similar demographic characteristics and typical findings of each of these entities. The following table shows the sensitivity, specificity, PPV, NPV and LR obtained by the different classification criteria:

	Calin	ACR	Amor	ESSG	ASAS	3° Workshop
Sensitivity (%)	81	64	53	97	97	64
Specificity (%)	100	100	47	57	50	100
PV (%) +	100	54	50	69	66	100
PV (%)  –	84	73	50	95	95	73
LR	∞	∞	1	2.19	1.94	∞

Conclusion:  the highest sensitivity was observed by applying the ESSG, ASAS and Calin criteria. The highest specificity was obtained by applying the Calin, ACR and Third International Workshop criteria. We observe, in this study, that Calin’s criteria showed excellent specificity, keeping a good sensitivity and high positive predictive values and likelihood ratios.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/evaluation-and-comparison-of-performance-of-different-classification-criteria-for-reactive-arthritis/