Table 3. Examples of Biomarkers for Early Diagnosis of Neurodegenerative Diseases.

biomarker	biomarker type	diagnostic test	sample type	technique	sensitivity	limit of detection	sample volume	test time	cost	ref
tau	protein	ELISA	cerebrospinal fluid	immunoassay	90–100%	0.013 ng/mL	150 μL	4 h	$300–$500	(135, 136)
beta-amyloid 42	protein	ELISA	cerebrospinal fluid	immunoassay	80–90%	23.9 pg/mL	200 μL	4–6 h	$250–$400	(137, 138)
alpha-synuclein	protein	ELISA	cerebrospinal fluid	immunoassay	83–96%	0.02 ng/mL	200 μL	5 h	$350–$500	(127, 139−141)
neurofilament light chain	protein	ELISA	blood	immunoassay	90–100%	5.1 pg/mL	200 μL	2–3 h	$150–$300	(142−145)
glial fibrillary acidic protein	protein	ELISA	blood	immunoassay	80–95%	2.4 ng/mL	200 μL	4 h	$200–$400	(146, 147)
ubiquitin C-terminal hydrolase L1	protein	ELISA	blood	immunoassay	85–95%	0.005 ng/mL	100 μL	2 h	$200–$300	(148, 149)
amyloid beta 1–40	protein	ELISA	cerebrospinal fluid	immunoassay	80–90%	10 pg/mL	200 μL	4–6 h	$250–$400	(150, 151)
phosphorylated tau	protein	ELISA	cerebrospinal fluid	immunoassay	80–90%	0.8 pg/mL	150 μL	4 h	$300–$500	(152, 153)
total tau	protein	ELISA	blood	immunoassay	90–100%	4.4 pg/mL	200 μL	3–4 h	$150–$300	(154, 155)
neurogranin	protein	ELISA	cerebrospinal fluid	immunoassay	80–90%	0.1 ng/mL	200 μL	5–6 h	$350–$500	(156, 157)
chitinase-3-like protein 1	protein	ELISA	blood	immunoassay	80–90%	0.12 ng/mL	200 μL	3–4 h	$200–$400	(158−160)
beta-secretase 1	protein	ELISA	cerebrospinal fluid	immunoassay	85–95%	0.5 pg/mL	200 μL	5 h	$300–$500	(161, 162)