Comparing two clinical measurements: a linear mixed model approach

In this article, we extended the widely used Bland-Altman graphical technique of comparing two measurements in clinical studies to include an analytical approach using a linear mixed model. The proposed statistical inferences can be conducted easily by commercially available statistical software such as SAS. The linear mixed model approach was illustrated using a real example in a clinical nursing study of oxygen saturation measurements, when functional oxygen saturation was compared against fractional oxy-hemoglobin.