. 2024 Mar 2;70(3):538–550. doi: 10.1093/clinchem/hvad221

Table 2.

Coefficient estimates from linear mixed effects models on full (between-subjects) dataset. Bold entries indicate coefficient estimates significantly different from 0 (nominal α = 0.05). $A β_{42}$ , amyloid beta 1–42; CI, 95% confidence interval; MCI, mild cognitive impairment; $pTa u_{181}$ , phosphorylated tau 181; tTau, total tau.

	Aβ₄₂			pTau₁₈₁			tTau
Predictors	Estimates	CI	P	Estimates	CI	P	Estimates	CI	P
(Intercept)	1307.40	1262.09 to 1352.72	<0.001	17.11	16.25 to 17.96	<0.001	194.36	184.81 to 203.91	<0.001
Sarstedt 0.5 mL screw top, gentle extraction, frozen	Reference			Reference			Reference
Fisher 1.5 mL microcentrifuge, gentle extraction, frozen	−389.59	−434.33 to −344.85	<0.001	−0.05	−0.62 to 0.51	0.858	−5.93	−12.79 to 0.93	0.090
Fisher 2.0 mL cryovial, gentle extraction, frozen	−132.80	−229.27 to −36.34	0.007	−0.37	−1.49 to 0.75	0.515	0.49	−12.08 to 13.06	0.939
Matrix 1.0 mL cryotube, gentle extraction, frozen	−70.98	−168.64 to 26.68	0.154	0.91	−0.13 to 1.94	0.086
Sarstedt 2.5 mL non-stick, drip method, never frozen	153.82	99.25 to 208.39	<0.001	0.56	0.05 to 1.07	0.031	12.10	5.40 to 18.79	<0.001
Sarstedt 2.5 mL non-stick, drip method, frozen	−174.00	−257.73 to −90.27	<0.001	−4.60	−5.41 to −3.79	<0.001	−77.76	−111.72 to −43.80	<0.001
Age, centered at 60, years	−5.10	−8.42 to −1.77	0.003	0.32	0.25 to 0.38	<0.001	3.43	2.70 to 4.16	<0.001
Unimpaired	Reference			Reference			Reference
Impaired—other	107.83	−45.17 to 260.84	0.167	−0.08	−1.97 to 1.82	0.936	11.63	−15.43 to 38.69	0.399
MCI	−196.54	−282.89 to −110.20	<0.001	4.52	3.24 to 5.80	<0.001	43.14	28.62 to 57.66	<0.001
Dementia	−392.05	−517.20 to −266.89	<0.001	9.65	7.32 to 11.99	<0.001	125.05	91.75 to 158.35	<0.001
Aβ₄₂ reagent lot 470571	50.51	−29.05 to 130.07	0.213
Aβ₄₂ reagent lot 518749	6.06	−86.39 to 98.52	0.898
pTau₁₈₁ reagent lot 460998				0.60	−0.32 to 1.52	0.202
pTau₁₈₁ reagent lot 527946				−2.17	−3.13 to −1.21	<0.001
tTau reagent lot 456531							9.57	−3.28 to 22.43	0.144
Random effects
σ²	15541.60			1.29			140.69
τ₀₀	23560.22 _{Reggieid:sample_date}			2.62 _{Reggieid:sample_date}			298.06 _{Reggieid:sample_date}
	115943.10 _Reggieid			77.19 _Reggieid			7334.23 _Reggieid
ICC	0.90			0.98			0.98
N	721 _Reggieid			721 _Reggieid			588 _Reggieid
	902 _{sample_date}			902 _{sample_date}			654 _{sample_date}
Observations	1245			1244			903
Marginal R²/conditional R²	0.223/0.922			0.176/0.987			0.192/0.985