Articular 18Fluorodeoxyglucose Uptake Is Associated With Clinically Assessed Swollen Joint Count in Patients With Rheumatoid Arthritis

Iván Ferraz-Amaro; Arif Sheikh; Berna Polack; Jon T. Giles; Joan M. Bathon

doi:10.3899/jrheum.220231

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Table 1.

Baseline characteristics of 34 patients with RA.

	N = 34
Age, yrs	54 (10)
Female, n (%)	27 (79)
Waist circumference, cm	89 (16)
BMI, kg/m²	29 (6)
Systolic BP, mmHg	114 (16)
Diastolic BP, mmHg	70 (9)
Current smoking, n (%)	7 (26)
Hypertension, n (%)	8 (24)
Diabetes, n (%)	3 (9)
Statin therapy, n (%)	2 (6)
CRP, mg/L, median (IQR)	2.98 (1.12-6.60)
RA-related characteristics
Disease duration, yrs, median (IQR)	9 (3-14)
RF, n (%)	15 (44)
ACPA, n (%)	24 (71)
DAS28-CRP	3.72 (1.06)
CDAI, median (IQR)	17 (9-26)
Tender joint count, median (IQR)	6 (2-11)
Swollen joints, median (IQR)	7 (3-12)
HAQ, median (IQR)	1.11 (0.69-1.55)
NSAIDs, n (%)	7 (21)
Prednisone, n (%)	8 (24)
Methotrexate, n (%)	26 (76)
Sulfasalazine, n (%)	2 (6)
Hydroxychloroquine, n (%)	4 (12)
Leflunomide, n (%)	2 (6)
Biologic therapy, n (%)	12 (35)
Anti-TNF therapy, n (%)	7 (21)

Values are expressed as mean (SD) unless otherwise indicated. ACPA: anticitrullinated protein antibody; BP: blood pressure; CDAI: Clinical Disease Activity Index; CRP: C-reactive protein; DAS28: Disease Activity Score in 28 joints; HAQ: Health Assessment Questionnaire; NSAID: nonsteroidal antiinflammatory drug; RA: rheumatoid arthritis; RF: rheumatoid factor; TNF: tumor necrosis factor.

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Table 2.

Correlation between FDG joint uptake^{^a} and disease activity variables.

	TJC28		SJC28		DAS28		CDAI		SDAI		HAQ		CRP
	ρ	P	ρ	P	ρ	P	ρ	P	ρ	P	ρ	P	ρ	P
wj25SUV	0.20	0.31	0.39	0.04	0.32	0.09	0.32	0.09	0.42	0.02	0.11	0.55	−0.002	0.99
wj50SUV	0.17	0.37	0.39	0.04	0.30	0.12	0.30	0.11	0.40	0.03	0.09	0.64	−0.020	0.92
wj75SUV	0.16	0.42	0.37	0.045	0.28	0.14	0.29	0.13	0.38	0.04	0.07	0.71	−0.020	0.92
wjMaxSUV	0.14	0.47	0.36	0.05	0.27	0.16	0.27	0.15	0.37	0.05	0.07	0.71	−0.022	0.91

Values in bold are statistically significant.
↵^a Weighted joint volume SUVs (wjSUV) representing 25%, 50%, 75%, and maximum (100%) uptake (wj25SUV, wj50SUV, wj75SUV, and wjMaxSUV, respectively). CDAI: Clinical Disease Activity Index; HAQ: Health Assessment Questionnaire; DAS28: Disease Activity Score in 28 joints; CRP: C-reactive protein; FDG: ¹⁸F-fluorodeoxyglucose; ρ: Spearman rho; SDAI: Simple Disease Activity Index; SJC28: 28-joint swollen joint count; TJC28: 28-joint tender joint count.

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Table 3.

Association of disease characteristics with FDG uptake^{^a} in the 34 patients with RA.

	β (95% CI), P
	wj25SUV	wj50SUV	wj75SUV	wjMaxSUV	SJC
Disease duration, yrs	0.44 (−0.02 to 0.89), 0.06	0.45 (−0.02 to 0.92), 0.06	0.46 (−0.01 to 0.93), 0.06	0.46 (−0.02 to 0.94), 0.06	0.05 (−0.09 to 0.18), 0.47
RF	5.3 (−3.2 to 13.7), 0.21	5.3 (−3.5 to 14.1), 0.23	5.3 (−3.6 to 14.2), 0.23	5.4 (−3.5 to 14.3), 0.23	0.92 (−2.52 to 4.35), 0.59
logCRP, mg/dL	−0.06 (−0.26 to 0.14), 0.54	−0.07 (−0.37 to 0.24), 0.65	−0.10 (−0.50 to 0.31), 0.63	−0.11 (−0.60 to 0.37), 0.63	−0.17 (−1.69 to 1.36), 0.83
ACPA	−1.1 (−10.8 to 8.7), 0.82	−1.5 (−11.6 to 8.6), 0.77	−1.6 (−11.7 to 8.6), 0.76	−1.5 (−11.8 to 8.7), 0.76	−3.56 (−7.10 to −0.02), 0.049
DAS28	2.6 (−1.2 to 6.4), 0.17	2.4 (−1.5 to 6.4), 0.21	2.4 (−1.5 to 6.4), 0.22	2.5 (−1.5 to 6.5), 0.21	3.18 (2.08 to 4.27), < 0.001
CDAI	0.32 (−0.02 to 0.66), 0.07	0.30 (−0.05 to 0.66), 0.09	0.30 (−0.05 to 0.67), 0.09	0.31 (−0.05 to 0.7), 0.09	0.37 (0.31 to 0.43), < 0.001
SDAI	0.34 (0.03 to 0.65), 0.04	0.32 (0.00 to 0.65), 0.05	0.33 (−0.01 to 0.66), 0.53	0.33 (0.00 to 0.66), 0.05	0.31 (0.23 to 0.39), < 0.001
TJC28	0.40 (−0.46 to 1.26), 0.35	0.36 (−0.54 to 1.25), 0.42	0.36 (−0.55 to 1.26), 0.42	0.37 (−0.54 to 1.28), 0.41	0.66 (0.41 to 0.90), < 0.001
SJC28	0.94 (0.15 to 1.74), 0.02	0.93 (0.11 to 1.76), 0.03	0.95 (0.11 to 1.78), 0.03	0.96 (0.12 to 1.80), 0.03	–
HAQ	0.25 (−6.75 to 7.25), 0.94	0.30 (−6.91 to 7.50), 0.93	0.28 (−7.02 to 7.57), 0.94	0.24 (−7.10 to 7.59), 0.95	0.43 (−2.11 to 2.96), 0.73
NSAIDs	−5.4 (−15.8 to 4.9), 0.29	−5.4 (−16.1 to 5.2), 0.30	−5.5 (−16.3 to 5.3), 0.30	−5.5 (−16.4 to 5.4), 0.30	−3.48 (−7.55 to 0.60), 0.09
Prednisone	2.0 (−8.6 to 12.6), 0.70	1.8 (−9.1 to 12.8), 0.73	1.8 (−9.2 to 12.9), 0.73	1.8 (−9.3 to 13.0), 0.74	1.25 (−2.85 to 5.35), 0.54
Methotrexate	−1.1 (−13.1 to 11.0), 0.86	−1.0 (−13.5 to 11.5), 0.87	−1.1 (−13.7 to 11.6), 0.86	−1.1 (−13.8 to 11.6), 0.86	−2.95 (−7.43 to 1.53), 0.19
Biologic therapy	6.1 (−2.5 to 14.7), 0.16	6.6 (−2.3 to 15.5), 0.14	6.8 (−2.3 to 15.8), 0.14	6.9 (−2.2 to 15.9), 0.13	0.25 (−3.34 to 3.84), 0.89
Anti-TNF therapy	8.8 (−1.3 to 19.0), 0.09	9.1 (−1.4 to 19.7), 0.09	9.3 (−1.4 to 19.9), 0.09	9.4 (−1.2 to 20.1), 0.08	−1.19 (−5.41 to 3.03), 0.57

Values in bold are statistically significant.
↵^a Weighted joint volume SUVs (wjSUV) representing 25%, 50%, 75%, and maximum (100%) uptake (wj25SUV, wj50SUV, wj75SUV, and wjMaxSUV, respectively). ACPA: anticitrullinated protein antibody; DAS28: Disease Activity Score in 28 joints; CDAI: Clinical Disease Activity Index; NSAID: nonsteroidal antiinflammatory drug; HAQ: Health Assessment Questionnaire; RA: rheumatoid arthritis; RF: rheumatoid factor; SDAI: Simplified Disease Activity Index; SJC28: 28-joint swollen joint count; TJC28: 28-joint tender joint count; TNF: tumor necrosis factor.