Supportive CSF biomarker evidence to enhance the National Institute on Aging-Alzheimer's Association criteria for diagnosis of Alzheimer's type dementia – A study from Southern India

• CSF biomarkers as supportive evidence for the current diagnostic criteria of AD was assessed.
• The ratio of p-tau/t-tau was significantly different between mild and moderate to severe AD.
• p-tau/t-tau and p-tau/Aβ ratio are reliable indicators of severity of dementia.

The present study was undertaken to validate the measurement of biomarkers as a supplement to the latest diagnostic criteria for Alzheimer disease (AD) dementia by National Institute on Aging-Alzheimer's Association (NIA-AA) work group using a sample attending a tertiary care center in Southern India. A total of 20 subjects diagnosed clinically as Alzheimer's dementia according to the NIA-AA criteria for AD were included in the study. The CSF biomarkers Aβ42, t-tau, and p-tau181 were assessed. The biomarker results were compared among mild and moderate to severe AD as defined in the NIA-AA work group guidelines. The results revealed that the amount of Aβ42 was very low in all the 20 samples (<50 pg/ml) collected from mild AD cases with CDR score of 1 (n = 8), and moderate to severe AD cases with CDR >1 (n = 12). t-tau and p-tau levels were in the range of 39.45 ± 5.09 pg/ml and 13.06 ± 7.32 pg/ml for CDR 1 group. t-tau and p-tau levels were in the range of 49.9 ± 11.28 pg/ml and 33.94 ± 15.13 pg/ml for moderate to severe cases. Analysis of the data revealed statistically significant differences in the p-tau/t-tau ratio and p-tau/Aβ ratio between CDR 1and CDR >1 AD cases (p < 0.001) suggesting that p-tau/t-tau and p-tau/Aβ ratio are good indicators of severity of dementia with discriminative value in differentiating mild AD from moderate to severe AD.