Immunoassay of thyroid peroxidase autoantibodies: diagnostic performance in automated third generation methods. A multicentre evaluation

Abstract

These findings confirm the improvement of harmonisation between different methods of automated third generation TPOAb assays. Nevertheless, further efforts should be made in the definition of the positive cut-off concentration to avoid misclassification of AITD patients as well as in a new international reference preparation and in the autoantigen purification modality.

Definition of the upper reference limit for thyroglobulin antibodies according to the National Academy of Clinical Biochemistry guidelines: comparison of eleven different automated methods

“…Specifically, there were relevant differences between methods in terms of medians (31-fold) ( p  < 0.05, Kruskal–Wallis test) and interquartile ranges. These discrepancies were not expected and not easily explained; in fact, in recent decades, there have been significant improvements in harmonization between methods [39], resulting from the high level of automation of analytical procedures and the use of the same reference preparation (IRP MRC 65/93). Moreover, analytical imprecision seems not contribute to the above differences, as the values declared by the individual manufacturer were essentially overlapping (although obtained with different protocols, some of them standardized, some others not) and in general lower than 10% for both intra- and inter-assay imprecision (Table 1).…”

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

“…There are no clear explanations for these discrepancies. In fact, over the years, there has been an improvement in the harmonization among methods, due to automation of the analytical procedures and the use of the same reference preparation (MRC 66/387) [ 10 ]. Moreover, it does not seem that the intra-method analytical imprecision contributes to these differences, since the precision performances declared by the individual manufacturer are essentially overlapping (Table 1 ).…”

“…In recent years, refinements in autoantigen preparation and better selection of polyclonal and monoclonal antibodies have led to a new (third) generation of automated quantitative immunoassays (IMAs) with improved sensitivity and specificity for the measurement of TPOAbs [ 4 , 5 ]. Despite their recently expanded use in clinical laboratories [ 6 – 8 ], it is yet unclear whether these more-sensitive automated third-generation IMAs have made improvements in terms of diagnostic accuracy and harmonization compared with previous methods [ 9 , 10 ]. Hence, further efforts in defining the threshold values of positivity need to be made in order to avoid misclassification of patients with AITD [ 9 ].…”

“…Hence, in developing commercial methods for TPOAbs quantification, manufacturers are faced with difficulties in following the NACB recommendations. Consequently, results obtained by different researchers using different analytical methods show a wide variation in URLs [ 8 – 10 , 13 , 14 ]. In addition, the definition of reference intervals for TPOAbs has limitations due to the natural history of AITD, because a large number of individuals may have specific autoantibodies in serum 10–15 years before the onset of these diseases.…”

“…Taking into account that TPOAbs reference limits are method dependent and often arbitrarily established in the current laboratory practice [ 9 , 10 , 16 ], the aim of this study was to determine the URL of TPOAbs in a male sample according to the NACB guidelines, and to compare it with that obtained in a female group, applying and comparing five third-generation commercial automated IMA platforms.…”