Correlation of measured 25(OH)D concentration (nmol/L) and predicted 25(OH)D concentration using (A) a multiple linear regression model; and (B) a radial basis function support vector regression model.

<p>Correlation of measured 25(OH)D concentration (nmol/L) and predicted 25(OH)D concentration using (A) a multiple linear regression model; and (B) a radial basis function support vector regression model.</p

Performance demonstration of SVR and MLR in a simple scenario (two-dimensional case).

<p>The black dots indicate actual simulation data set. The solid curve denotes SVR regress line and the dot line represents the MLR regression line. The simulation data set is randomly generated by MATLAB.</p

ROC curves of MLR and RBF SVR.

<p>ROC curves showing true-positive rates (sensitivity) plotted against the false-positive rate for different cut off points of the quantified components of MLR (gray diamonds) and RBF SVR (black circles). The points highlighted are 25(OH)D scores of 75 nmol/l for MLR and RBF SVR. The area under the curve is 0.79 and 0.87 for MLR and RBF SVR respectively.</p

Accuracy of predicted 25(OH)D score in each quintile of 25(OH)D concentration.

<p>Accuracy of predicted 25(OH)D score in each quintile of 25(OH)D concentration.</p

Predicted 25(OH)D concentration and mean absolute difference between predicted and measured 25(OH)D level (nmol/L).

<p>RBF SVR, radial basis function support vector regression (nonlinear support vector regression).</p><p>MLR, multiple linear regression.</p><p>Mean absolute difference is the average of the absolute differences between the predicted and measured values.</p

Bland – Altman plots of measured 25(OH)D concentration compared to predicted scores from (A) a MLR model; (B) a RBF SVR model.

<p>The solid lines indicate the mean bias (middle line) and 95% limits of agreement (top and bottom lines). All measurements are in nmol/L.</p

Recent studies using a multiple linear regression prediction model for 25(OH)D concentration.

<p>Recent studies using a multiple linear regression prediction model for 25(OH)D concentration.</p

Percentage of individuals classified by quintiles of measured 25(OH)D concentration and predicted 25(OH)D score.

<p>Percentage of individuals classified by quintiles of measured 25(OH)D concentration and predicted 25(OH)D score.</p

Bland-Altman plot of serum 25(OH)D concentrations at laboratory B (LC-MS/MS) <i>v</i> certified laboratory (LC-MS/MS).

<p>The solid lines indicate the mean bias and the dotted lines indicate the 95% limits of agreement. 25(OH)D, 25-hydroxyvitamin D.</p

Analytical characteristics of the laboratories using assays based on liquid chromatography-tandem mass spectrometry.

<p>CV, Coefficients of Variation; LOD, analytical Limit of Detection; 25(OH)D₃, 25-hydroxyvitamin D₃; 25(OH)D₂, 25-hydroxyvitamin D₂; 3-epi-25(OH)D₃, c3 epimer; NR, not reported.</p><p>Analytical characteristics of the laboratories using assays based on liquid chromatography-tandem mass spectrometry.</p