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Table 2 Impact of within-day and between day variations on assessment of biochemical and combined risk for Down syndrome

From: The impact of temporal variability of biochemical markers PAPP-A and free β-hCG on the specificity of the first-trimester Down syndrome screening: a Croatian retrospective study

   Free β-hCG
MoM
PAPP-A
MoM
Biochemical risk
(1 in)
Combined risk
(1 in)
Within-day variations of calculated risk High risk *     
  Mean ± SD 1.87 ± 0.08 0,29 ± 0,01 52.6 ± 6.2 154.4 ± 16.1
  CV† (%) 4.27 3.45 11.72 10.45
  Medium risk **     
  Mean ± SD 0.59 ± 0,03 0,29 ± 0,01 732.6 ± 76.0 699.9 ± 77.2
  CV† (%) 5.08 3.45 10.37 11.03
  Low risk ***     
  Mean ± SD 1.87 ± 0.08 1.26 ± 0.05 3060.8 ± 323.5 2527.7 ± 328.3
  CV† (%) 4.27 3.97 10.57 12.98
  Human serum     
  Mean ± SD 1.47 ± 0.07 1.79 ± 0.06 8668.2 ± 819.4 7313.9 ± 900.9
  CV† (%) 4.76 3.35 9.45 12.32
Between-day variations of calculated risk High risk *     
  Mean ± SD 1.70 ± 0.09 0.27 ± 0.01 45.39 ± 5.5 145.6 ± 18.2
  CV† (%) 5.26 3.43 12.12 12.50
  Medium ris k **     
  Mean ± SD 0.59 ± 0.03 0.27 ± 0.01 661.4 ± 68.7 646.1 ± 68.58
  CV† (%) 4.3 3.43 10.39 11.54
  Low risk ***     
  Mean ± SD 1.70 ± 0.09 1.26 ± 0.05 2442.6 ± 304.6 1993.3 ± 219.7
  CV† (%) 5.26 4.28 12.47 11.02
  Human serum     
  Mean ± SD 1.36 ± 0.08 1.76 ± 0.09 7446.5 ± 796.8 6146.4 ± 785.4
  CV† (%) 6.17 5.20 10.70 12.77
  1. *Biochemistry: Control 3 (free β-hCG) + Control 1 (PAPP-A); Patient: 25 years, non-smoker, 67 kg, CRL = 45 mm, NT = 1.5 mm
  2. **Biochemistry: Control 2 (free β-hCG) + Control 1 (PAPP-A); Patient: 25 years, non-smoker, 67 kg, CRL = 45 mm, NT = 1.8 mm
  3. ***Biochemistry: Control 3 (free β-hCG) + Control 2 (PAPP-A); Patient: 25 years, non-smoker, 67 kg, CRL = 45 mm, NT = 1.8 mm
  4. CV† - coefficient of variation