Pearson (Spearman) correlation Pearson (Spearman)
  N mean sd (10th – 90th percentile) x y z ICC
NAPAP (X) (o.d.) 1168 0.176 0.352 (0.000,0.675) 1 0.423 0.19 0.614
-0.353 -0.155 -0.515
salicylates (Y) (mg%) 1168 15.8 19.2 (10.0,35.0)   1 0.068 0.404
-0.081 -0.389
serum creatinine (Z) (mg/dL) 1168 1.02 0.37 (0.69,1.50)     1  
NAPAP value at the baseline (1968) clinic visit.
Individual salicylate values were obtained in grouped form (1=0-19 mg%/2=20-49 mg%/3=50-99 mg%/4=100+mg%) at the baseline (1968) clinic visit, and assigned scores of 10 mg%, 35 mg%, 75 mg% and 100 mg%, respectively.
Spearman correlations are estimated based on (18)
N: Number of subjects with serum creatinine, NAPAP and salicylates, available at the baseline (1968) clinic visit
ICC: Intraclass Correlation among replicate urine values (based on urine specimens obtained at the baseline clinic visit and 2 additional urine specimens obtained at home on different days).
Table 4: Descriptive statistics for NAPAP, salicylates and serum creatinine at the baseline visit, Swiss Analgesic Study, n=1168.