Table 3. Protein biomarker candidates with their CVs and RCVs.

Protein IDs	Gene name	Protein name	CVt / CVg [%]	RCVt / RCVg [%]	PD/PDD	AD	HD	MS	Other diseases
P00738	HP	Haptoglobin	10.2 / 101.5	28.2 / 281.4	[37]	[37, 38]		[39]
P02675	FGB	Fibrinogen beta chain	13.4/ 45.5	37.0 / 126.0	[37]		[40]
P02652	APOA2	Apolipoprotein A-II	17.3 / 46.6	48.0 / 129.3	[37]			[41]	[42]
P06727	APOA4	Apolipoprotein A-IV	11.3 / 33.1	31.4 / 91.7				[39, 41]
P61769	B2M	Beta-2-microglobulin	29.3 / 52.5	81.3 / 145.5	[37]	[43]
P02649	APOE	Apolipoprotein E	6.5 / 31.8	17.9 / 88.2		[44, 45]		[46]	[42, 44]
P02753	RBP4	Retinol-binding protein 4	15.1 / 27.7	42.0 / 76.9	[37]		[40]	[41]
P25311	AZGP1	Zinc-alpha-2-glycoprotein	4.5 / 23.5	12.6 / 65.1	[37]	[47]
P02774	GC	Vitamin D-binding protein	5.5 / 22.6	15.2 / 62.7		[44]		[39, 41]	[44]
P02749	APOH	Beta-2-glycoprotein 1	7.7 / 23.6	21.2 / 65.5	[37]		[40]	[41]
P00441	SOD1	Superoxide dismutase [Cu-Zn]	15.9 / 32.3	44.1 / 89.6		[37]			[37]
P02768	ALB	Serum albumin	6.9 / 21.0	19.0 / 58.3		[48]		[41]
P01024	C3	Complement C3	2.6 / 19.0	7.2 / 52.6			[40]	[41, 49, 50]
P05090	APOD	Apolipoprotein D	6.1 / 19.9	17.0 / 55.1		[37]		[41, 49]
P36222	CHI3L1	Chitinase-3-like protein 1	5.2 / 30.2	14.5 / 83.8		[44, 45]		[39]	[44]
P02766	TTR	Transthyretin	10.7 / 19.0	29.5 / 52.8		[44]			[37]
Q13822	ENPP2	Extonucleotide pyrophosphatase	5.6 / 14.7	15.5 / 40.9		[44]	[40]		[37]
Q92876	KLK6	Kallikrein-6	5.0 / 16.4	13.7 / 45.5	[37]	[37]		[41, 49]
P01034	CST3	Cystatin-C	10.6 / 15.4	29.4 / 42.7	[37]	[38, 44]		[41, 49]	[44]
P10909	CLU	Clusterin	10.2 / 12.8	28.2 / 35.4	[38]	[44]		[41, 49]	[44]

20 protein biomarker candidates with their respective intra- and interindividual coefficient of variation (CV_t and CV_g) and reference change values (RCV_t and RCV_g) are listed as well as the studies in which they have been proposed as biomarker candidate.