Table 2

Papers on the diagnosis of mimicking disease in patients with RA

PaperDesignStudy populationDiagnostic test for mimicking diseaseReference standard for mimicking disease*Time intervalSens, %
(95% CI)†		Spec, %
(95% CI)†		RoB
Fan, 201617CSEstablished RA (n=279), with final diagnosis:

  • RA with concomitant diagnosis of FM according to ACR criteria (n=52) or to rheumatologist (n=93)

  • RA without FM (according to ACR criteria: n=227; or to rheumatologist: n=186)

Fibromyalgia Rapid Screening Tool ≥5 (/6)FM according to:

  • 1990 ACR criteria119

  • Rheumatologist’s opinion

Concurrent 71 (42 to 92)
 83 (51 to 95)		 84 (79 to 89)
 88 (83 to 91)		H
Ghib, 2018‡18CCEstablished RA (n=20):

  • RA with FM (n=10)

  • RA without FM but with VAS-pain ≥50 (n=10)

MicroRNA-143 >1.0FM: NRNR9070H
Salaffi, 201820CSEstablished RA (n=292), with final diagnosis:

  • RA with FM (n=43)

  • RA without FM (n=249)

Derived DAS28 patient-reported components (DAS28-P)* >0.6312
*(0.56×√TJC +0.014× GH)/DAS28		FM according to ACR 2010 criteria119NR81 (67 to 92)80 (75 to 85)H
Sato, 201219CSEstablished RA (n=118), with final diagnosis:

  • Flare of RA (n=18)

  • Non-infectious complications (n=23)

  • Non-bacterial infection (n=15)

  • Bacterial infection (n=62)

Procalcitonin ≥0.5 ng/mL
Procalcitonin ≥0.2 ng/mL
WCC >8500/m3
CRP ≥0.3 mg/dL
ESR >15 mm/hour
Procalcitonin ≥0.5 ng/mL+WCC >8500/m3		Bacterial Infection: symptoms, bacterial culture tests, imaging studies, and response to antibiotic therapyWithin period of hospital admission26
34
66
70
98
21		98
89
59
5
9
1		L

  • *A clinical diagnosis according to a rheumatologist was deemed as the appropriate reference standard.

  • †95% CI, if reported.

  • ‡Abstract.

  • ACR, American College of Rheumatology; CC, case control; CRP, C reactive protein; CS, cross-sectional; DAS28, Disease Activity Score Assessing 28 joints; ESR, erythrocyte sedimentation rate; FM, fibromyalgia; GH, global health; H, high (red); L, low (green); NR, not reported; RA, rheumatoid arthritis; RoB, risk of bias; sens, sensitivity; spec, specificity; TJC, tender joint count; VAS, Visual Analogue Scale; WCC, white cell count.;