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Table 2 Methodological analyses in saliva lab tests for creatinine, uric acid, and potassium in control group: blind duplicates, site of collection, day-to-day variability, time of collection, and freezing/thawing effect (mean ± SEM)

From: Saliva for assessing creatinine, uric acid, and potassium in nephropathic patients

   P R
Blind duplicates first duplicate second duplicate   
 Creatinine, μmol/L 11.5 ± 3.9 11.7 ± 1.5 0.321 0.748 §
 Uric acid, μmol/L 261 ± 166 251 ± 145 0.187 0.993*
 Potassium, mmol/L 22.2 ± 6.6 22.5 ± 5.9 0.349 0.997*
Site of collection right vestibulum left vestibulum  
 Creatinine, μmol/L 11.7 ± 4.1 11.4 ± 1.6 0.628 0.728 §
 Uric acid, μmol/L 262 ± 74 264 ± 65 0.865 0.991*
 Potassium, mmol/L 23.2 ± 7.5 23.6 ± 5.8 0.791 0.898*
Day-to-day variability first day second day  
 Creatinine, μmol/L 11.5 ± 3.9 11.5 ± 2.0 0.723 0.735 §
 Uric acid, μmol/L 261 ± 166 255 ± 165 0.790 0.677 §
 Potassium, mmol/L 22.2 ± 6.6 25.4 ± 6.7 0.389 0.620 §
Time of collection standard sample mid-morning sample  
 Creatinine, μmol/L 11.5 ± 3.9 9.1 ± 1.5 0.038 0.765
 Uric acid, μmol/L 261 ± 166 184 ± 102 < 0.001 0.915
 Potassium, mmol/L 22.2 ± 6.6 18.7 ± 5.9 < 0.001 0.728
Freezing/thawing effects standard sample frozen/thawed sample  
 Creatinine, μmol/L 11.5 ± 3.9 10.5 ± 1.4 0.488 0.899
 Uric acid, μmol/L 261 ± 166 216 ± 118 < 0.001 0.818
 Potassium, mmol/L 22.2 ± 6.6 21.4 ± 5.7 0.389 0.829
  1. Non-stimulated fresh saliva collected early in the morning after an overnight fast with the use of a synthetic swap
  2. Control group N = 15 (14 for creatinine)
  3. * P < 0.001, § P ≤ 0.01