Establishment of the upper reference limit for thyroid peroxidase autoantibodies according to the guidelines proposed by the National Academy of Clinical Biochemistry: comparison of five different automated methods

Table 1 The main features of the five automated immunoassay methods, as declared by the manufacturers

System	Method	Tracer	Antigen	Imprecision (%): intra-assay; between-assay	Imprecision (%): total	LoD (IU/mL)	LoQ (IU/mL)
IMM	CLIA	Luminescence: adamantyl dioxetane phosphate	Native TPO	4.9–6.3; nr	6.1–8.1	5.0	nr
MAG	CLIA	Luminescence: N-(aminobutyl)-N-(ethyl)-isoluminol	Native TPO	6.8–7.3; 7.4–7.6	nr	0.38	nr
KRY	FIA	Fluorescence: europium cryptate/XL 665	Native TPO	2.1–7.6; 5.8–16.0	nr	1.8	9.0
PHA	FEIA	Fluorescence: β-D-galactosidase; 4-methyl-umbelliferyl-β-D-galactoside	Recombinant TPO	4.1–4.7; 2.5–4.8	nr	nr	nr
LIA	CLIA	Luminescence: isoluminol derivative	Recombinant TPO	3.6–6.2; 4.7–6.9	nr	0.6	1.0

CLIA chemiluminescence immunoassay, FEIA fluorescence enzyme immunoassay, FIA fluoroimmunoassay, IMM Immulite 2000 XPi, KRY Kryptor Compact Plus, LIA Liaison XL, LoD limit of detection, LoQ limit of quantitation, MAG Maglumi 2000 Plus, nr not reported, PHA Phadia 250, TPO thyroid peroxidase

ISSN: 2038-3274