Diagnostic accuracy of biomarker combinations in the A/T/N classification for Alzheimer’s disease (P4.182)

Objective: We propose to evaluate the differents combinations of A+/T+/N+ biomarkers and diagnostic accuracy in comparison with traditional clinical diagnosis. Background: “A/T/N” classification system was proposed to clarify the heterogeneity of AD biomarkers. AD biomarkers were divided into 3 binary categories (positive or negative) based on the nature of the pathophysiology that each measures. “A” refers to the value of a β-amyloid biomarker: amyloid PET or CSF Aβ42); “T,” the value of a tau biomarker: CSF phospho tau (pT), or tau PET; and “N,” biomarkers of neurodegeneration or neuronal injury: [(18)F]-fluorodeoxyglucose-PET(FDG), MRI, or CSF total tau (tT). Despite it has been conceived as a descriptive system it could be useful for diagnostic procedures. There is no data about which biomarker combination is better. Design/Methods: We assessed 253 medical records of patients who underwent CSF, PET-FDG, PET-PIB and MRI scanner and diagnosed with dementia of Alzheimer (n=44) or non/Alzheimer type (n=209). Each one were classified in different A+/T+/N+ combinations. Sensitivity (S), specificity (Sp), negative (NPV) and positive predictive (PPV) value was assessed. Results: ATN1(Aβ/pT/tT):Sp=0,67, S=0,68, PPV=0,3, NPV=0,91. ATN2(PIB/pT/tT):Sp=0,81, S=0,86, PPV=0,12, NPV=0,97. ATN3(Aβ/pT/FDG):Sp=0,77, S=0,85, PPV=0,11, NPV=0,96, ATN4(Pib/pT/FDG):Sp=0,81, S=0,86, PPV=0,12, NPV=0,97. Conclusions: According to this data the best combination of biomarkers to predict clinical diagnosis of AD include CSF Aβ and phospho tau in CSF (as “A” and “T”) and FDG abnormalities as “N”. However, we found low NPV values in every “A/T/N” combination. Disclosure: Dr. Chrem Mendez has nothing to disclose. Dr. Calandri has nothing to disclose. Dr. Demey has nothing to disclose. Dr. Pertierra has nothing to disclose. Dr. Russo has nothing to disclose. Dr. Surace has nothing to disclose. Dr. Martinetto has nothing to disclose. Dr. Campos has nothing to disclose. Dr. Vazquez has nothing to disclose. Dr. Sevlever has nothing to disclose. Dr. Allegri has nothing to disclose.