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Table 5 Estimates of the change in serum 25(OH)D concentration over time and by cumulative vitamin D3 dose

From: Randomized placebo-controlled trial of high-dose prenatal third-trimester vitamin D3 supplementation in Bangladesh: the AViDD trial

Model parameters (units)

[25(OH)D] over time (days) in Vitamin D group1

[25(OH)D] over time (days) among all participants2

[25(OH]D] by dose (mcg) among all participants2

β

95% CI [LB, UB]

β

95% CI [LB, UB]

β

95% CI [LB, UB]

Reference

Day 0 (baseline)

Placebo group at Day 0 (baseline)

0 mcg of Vitamin D

25(OH)D at ref. point (nmol/L)

45.5

[41.0, 49.9]

44.4

[39.7, 49.1]

42.1

[39.1, 45.1]

Difference in 25(OH)D between groups at day 0 (nmol/L)

–

1.1

[−5.3, 7.6]

–

Decay rate (days -1 or mcg -1 )

0.04

[0.03, 0.05]

0.04

[0.03, 0.05]

0.0003

[0.0002, 0.0004]

Δ25(OH)D at steady-state in placebo group (nmol/L)

–

−7.1

[−12.3, -1.9]

–

Effect of vitamin D on Δ25(OH)D at steady-state (nmol/L)

94.4

[83.9, 104.9]

101.6

[89.7, 113.4]3

98.3

[88.7, 107.9]

Attained steady-state 25(OH)D (nmol/L)

139.9

[130.1, 149.6]

138.8

[127.4, 150.2]

140.4

[131.2, 149.6]

Adjusted R 2

0.72

0.75

0.75

AIC

–

3907.2

3904.4

  1. 180 participants in the vitamin D group, contributing 220 specimens. Negative exponential model (vitamin D group): [25(OH)D] t  = [25(OH)D] t = 0 + a 1(1 − e − kt); where t is time, a is the Δ25(OH)D (where Δ is the change from baseline) at steady-state in the placebo group, and k is the decay rate to the asymptote.
  2. 2 The models include 160 participants overall (n = 80 in each group) contributing 433 specimens. Negative exponential model (both groups):
  3. [25(OH)D] t  = [25(OH)D] t = 0 + β g + (gd + a 0)(1 − e − kt); where t is time, a is the Δ25(OH)D at steady-state in the placebo group, k is the decay rate to asymptote, g is group assignment and d is the difference in Δ25(OH)D between groups at steady-state,
  4. 3 Difference in Δ25(OH)D between placebo and vitamin D groups at modeled steady-state.