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. 2021 Jan 29;7(1):e001511. doi: 10.1136/rmdopen-2020-001511

Table 5.

Concise summary of papers on the assessment of inflammatory activity in RA patients with comorbidities that may influence the assessment

Papers/design Diagnostic tests (#: n) Reference standards (*: n)† Results RoB: *
Obesity
At patient level 		   
3 papers (3 CS)92 96 97
RA patients, n=756:

  • BMI <25, n=287+NR

  • BMI 25–30, n=33+NR

  • BMI >30, n=79+NR

  • MBDA score (1: 357)

  • Adjusted MBDA score (1:190, MBDAoriginal +67.175 – (0.79*age) -(1.74*BMI) + (0.018*age*BMI)

  • US: sum score of 28 joints (1: 76)

  • US-DAS28 (SJC based on - US findings, 1: 76)

  • SJC44 (1: 323)

  • Lower extremity SJC (1: 323)

  • CDAI (1: 357)

  • MBDA score (1: 190)

  • SJC28 (1: 76)

  • DAS28 (1: 76)

  • ACR core set measures (patient/physician global, ESR, TJC; 1: 323)

  • MBDA as diagnostic test with CDAI as reference standard: BMI <25: r=0.33, p=0.0004; BMI 25–30: r=0.28, p=0.002; BMI >30: r=−0.02, p=0.80

  • Adjusted MBDA as diagnostic test with MBDA as reference standard: All BMI categories: r=0.91, p<0.00001 (BMI categories and adjusted MBDA with CDAI as reference standard: NR)

  • US28 sum score as diagnostic test with SJC28 as reference standard, mean difference (ie, US28 sum score higher than SJC28): BMI <25: 0.429 (p=0.467); BMI 25–30: 1.818 (p=0.001); BMI>30: 1.600 (p=0.049)

  • US-DAS28 as diagnostic test with DAS28 as reference standard, mean difference (ie, US-DAS28 higher than DAS28): BMI <25: 0.014 (p=0.812); BMI 25–30: 0.175 (p=0.002); BMI >30: 0.011 (p=0.894)

In case of obesity (BMI >30), SJC increases correcting for ACR core set measures (patient/physician global, ESR, TJC):

  • Lower extremity SJC: OR 1.633 (p=0.005)

  • SJC44: OR 1.037 (p=0.090)

 M: 2
H: 1
At joint level    
1 paper (1 CS)91
RA patients, n=43:

  • BMI <25, n=17

  • BMI 25–30, n=12

  • BMI >30, n=14

 Clinically swollen joint (1: 43) US (PD; 1: 43) Per higher BMI category the chance of synovitis according to US decreased correcting for age, gender and clinically swollen joints (ie, the SJC overestimates disease activity in obese patients): OR BMI 0.52 (95%CI 0.30 to 0.93, p=0.03) M: 1
 Fibromyalgia
 At patient level 		   
3 papers (2 CS‡, 1 CC)93–95
RA patients, n=239

  • Without fibromyalgia, n=161

  • With fibromyalgia, n=78

  • SJC (1: 39)

  • DAS28 (1: 72)

  • CDAI (1: 72)

  • SDAI (1: 72)

  • Modified DAS28 (1: 130)

  • Modified CDAI (1: 130)

  • Modified SDAI (1: 130)

Modified: excluding TJC and patient’s global assessment of disease activity		 7-joint US score (GS/PD; 2: 111); DAS28 (1: 130); CDAI (1: 130); SDAI (1: 130) Correlation coefficient in patients without versus with fibromyalgia with 7-joint US score (GS/PD) as reference standard:

  • DAS28 (GS): r=0.39 (p<0.05) vs r=0.36 (p<0.05)

  • DAS28 (PD): r=0.35 (p<0.05) vs r=0.12 (ns)

  • CDAI (GS): r=0.57 (p<0.05) vs r=0.43 (p<0.05)

  • CDAI (PD): r=0.37 (p<0.05) vs r=0.01 (ns)

  • SDAI (GS): r=0.57 (p<0.05) vs r=0.38 (p<0.05)

  • SDAI (PD): r=0.38 (p<0.05) vs r=0.01 (ns)

  • SJC (GS) - synovitis: r=0.44 (p=0.015) vs ns

  • SJC (PD) - synovitis r=0.47 (p=0.008) vs ns

  • SJC (GS) - tenosynovitis: r=0.57 (p=0.001) vs ns

  • SJC (PD) - tenosynovitis: r=0.46 (p=0.011) vs ns




In patients with fibromyalgia a discrepancy between traditional and modified composite scores originates, with higher traditional scores in these patients. Mean increment (95% CI, p value), adjusted for age, sex and nodular disease:

  • DAS28-ESR: 1.50 (0.60–2.40, 0.001)

  • DAS28-CRP: 1.55 (0.63–2.48, 0.001)

  • CDAI: 10.78 (3.23–18.34, 0.006)

  • SDAI: 11.34 (3.80–18.89, 0.0158)

 M: 2
H: 1

*Number of studies.

†In patients with comorbidities that may influence the assessment of inflammatory activity, the traditional measures may not be trustworthy. Therefore, in studies assessing this population we considered (scores based on) established imaging measures as a more appropriate reference standard.

‡Abstract.

ACR, American College of Rheumatology; BMI, body mass index; CC, case-control; CDAI, Clinical Disease Activity Index; CRP, C reactive protein; CS, cross-sectional; DAS28, disease activity score assessing 28 joints; ESR, erythrocyte sedimentation rate; GS, Grey scale; H, high (red); L, low (green); M, moderate (yellow); MBDA, multi-biomarker disease activity; NR, not reported; ns, not significant; PD, power Doppler; r, correlation coefficient; RA, rheumatoid arthritis; RoB, risk of bias; SDAI, simplified disease activity index; SJC, swollen joint count; TJC, tender joint count; US, ultrasonography.