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Table 4 Comparison of the 4-spot method with a 24-h urine collection (n = 26)

From: Evaluating urinary estrogen and progesterone metabolites using dried filter paper samples and gas chromatography with tandem mass spectrometry (GC–MS/MS)

Variable 24 h urine collection (μg/day) 24 h urine collection (ng/mg-Cr) 4-spot (ng/mg-Cr) Difference [95% confidence interval] ICC
Estradiol 0.77 (0.30, 1.90) 1.73 (0.80, 3.26) 1.68 (0.92, 3.81) 0.16 [0.01, 0.31]* 0.97
Estrone 6.0 (3.3, 9.9) 13.7 (6.3, 19.2) 14.4 (7.1, 18.8) 0.8 [0.1, 1.4]* 0.98
5α-pregnanediol 34.9 (13.6, 88.4) 71.4 (28.9, 257.2) 60.9 (29.7, 242.0) − 11.6 [− 38.7, 15.6] 0.97
5β-pregnanediol 99.2 (60.7, 214.0) 243.9 (99.2, 408.9) 204.3 (113.5, 466.6) 44.0 [− 27.2, 115.2] 0.96
  1. Data presented as median (IQR)
  2. Differences were calculated using a signed rank test (4-spot—24 h assay), as variables were not normally distributed. Note that ICCs were calculated between measurements expressed in identical units. Results for the 24-h collection are reported as ng/mg-Cr for ICC calculation and also as μg/day, the usual units for reporting results of 24-h collections
  3. Cr creatinine, ICC intraclass correlation coefficient
  4. * Estrone p = 0.03, estradiol p = 0.0499