Fig. 4From: Development of a simple method for the analysis of phenylalanine in dried blood spot using tandem mass spectrometryBland-Altman plot of the difference between the new method and ELISA vs. the average of the two methods. The continuous line represents the mean of the differences between the two methods while the dotted lines represent the limits of agreement from − 1.96 SD to + 1.96 SDBack to article page