S100A8 and posterior cortical atrophy: In dogs ≥6 years of age, a uCalR of ≥5.2 [or ≥9.1] or a S100A8/A9USG of ≥96.3 differentiated patients with TCC/PCA from those with non-neoplastic causes of similar presenting signs (estimated prevalence of TCC/PCA in this population: 20%) with a NPV of 96–100% (1.000 [0.956] and 0.975, respectively) and a PPV of 29–31% (0.294 [0.308] and 0.301, respectively).