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Table 2 Characteristics of RA patients stratified by urinary Na/K ratio

From: Urinary sodium-to-potassium ratio associates with hypertension and current disease activity in patients with rheumatoid arthritis: a cross-sectional study

Urine Na/K ratio Tertile 1 Tertile 2 Tertile 3  
<  1.71   2.94 <
(N = 336) n = 112 (33.3%) n = 112 (33.3%) n = 112 (33.3%) P value *
Age, year 60.0 ± 13.2 62.4 ± 11.8 63.1 ± 11.0 0.143
Male sex, n (%) 10 (8.92) 22 (19.64) 25 (22.32) 0.001
Body mass index, kg/m2 22.0 ± 3.1 22.6 ± 3.7 23.4 ± 4.1 0.011
Smoking habit, n (%) 7 (6.25) 11 (9.82) 10 (8.93) 0.547
Daily salt intake (g/day) 6.09 ± 1.36 7.67 ± 1.44 9.66 ± 2.04 <  0.001
Laboratory data
 Serum Cre, mg/dL 0.69 ± 0.16 0.72 ± 0.27 0.66 ± 0.16 0.081
 eGFR, ml/min/1.73m2 72.9 ± 18.2 73.0 ± 18.3 77.8 ± 17.2 0.01
 CRP, mg/dL 0.32 ± 0.73 0.33 ± 0.65 0.45 ± 1.19 0.46
 RF, IU/mL 100.3 ± 302.5 142.5 ± 279.4 131.4 ± 289.0 0.246
 anti-CCP antibody, U/mL 201.8 ± 435.8 242.8 ± 446.3 223.5 ± 444.2 0.216
 MMP-3, ng/mL 73.8 ± 73.7 93.5 ± 86.0 96.3 ± 105.2 0.302
RA disease characteristics
 Disease duration, year 9.66 ± 9.62 10.91 ± 9.82 11.16 ± 9.32 0.117
 DAS28-ESR 2.40 ± 0.83 2.53 ± 0.96 2.74 ± 1.08 0.025
 DAS28-CRP 1.92 ± 0.73 2.01 ± 0.79 2.22 ± 1.00 0.042
Blood pressure
 SBP (Branchial), mmHg 120.4 ± 16.5 121.2 ± 16.4 126.9 ± 18.5 0.009
 DBP (Branchial), mmHg 69.2 ± 10.5 69.3 ± 11.3 72.9 ± 13.1 0.043
 Hypertension, n (%) 25 (22.3) 37 (33.0) 48 (42.9) 0.0011
Current RA therapeutics
 MTX use, n (%) 90 (80.3) 80 (71.4) 76 (67.9) 0.035
 Biological agent use, n (%) 63 (56.3) 55 (49.1) 56 (50.0) 0.386
 Prednisolone use, n (%) 17 (15.2) 23 (20.5) 30 (26.8) 0.04
  1. Continuous variables are presented as mean (± standard deviation) and categorical variables are presented as numbers (%). Estimated daily salt intake was calculated using Tanaka’s formula
  2. Abbreviations: RA rheumatoid arthritis, Cre creatinine, eGFR estimated glomerular filtration, RF rheumatoid factor, anti-CCP antibody anti-cyclic citrullinated peptide antibody, DAS28-ESR 28-joint disease activity score using erythrocyte sedimentation, CRP C-reactive protein, HAQ health assessment questionnaire, MTX methotrexate
  3. *P values are calculated using Cochran-Armitage trend test for categorical variables and Jonckheere-Terpstra trend test for continuous variables