Bland–Altman comparison for the interlaboratory canine urine cortisol
comparison study (n = 11), with simple linear
regression of the differences between laboratories. TVMDL used the
Immulite 2000 Xpi cortisol immunoassay, and AHDC-CU used the Immulite
1000 cortisol immunoassay. There was one freeze–thaw cycle for AHDC-CU;
there was none for TVMDL. The simple linear regression of the difference
followed the equation: y = –0.1834x + 2.1856. Thus, and in light of the
regression curve, there was a small positive constant bias most visible
at low concentration, and a small negative proportional bias at higher
concentration; none would significantly impact clinical interpretation.
AHDC-CU = Animal Health Diagnostic Center of Cornell University;
TVMDL = Texas A&M Veterinary Medical Diagnostic Laboratory.