Figure 1

Box-Jenkin plots of plasma creatinine values in plasma samples from A: 10 healthy dogs; group 1 (Sample no 1-10) and B: 10 dogs with expected intermediate values; group 2 (Sample no 11-20) and C: 10 azotemic dogs; group 3 (Sample no 21-30) analyzed 3 times in different batches by 10 laboratories in Northern Europe. The box represents the interquartile range from the 25^th to the 75^th percentile. The horizontal bar through the box is the median. The whiskers represent the main body of the data; that is, the upper or lower quartile ± 1,5× interquartile distance. Outlier values (outside the 1,5× interquartile distance) are represented by different symbols for each laboratory; grey squares represent one outlier batch from laboratory 3.