GPT and neoplasm: Using this threshold, 9/16 (56%) of the neuroblastoma serum specimens in the validation group were ALT+ and the serum-based CCA had a sensitivity of 100% (6/6), a specificity of 70% (7/10), and a concordance of 81% (13/16) compared with the matched-tumor-based PCR-CCA (Figure 6a).