Aim of the studyThe estimation of the upper reference limit (URL) for autoantibodies against thyroid peroxidase (TPOAbs) is a controversial issue, because of an uncertainty associated with the criteria used to correctly define the reference population. In addition, the URL of TPOAbs is method-dependent and often arbitrarily established in current laboratory practice. The aim of this study was to determine the reference limits of TPOAbs in a male sample according to the National Academy of Clinical Biochemistry (NACB) guidelines, and to compare them with those obtained in a female group, for five third-generation commercial-automated immunoassay (IMA) platforms.Methods120 healthy males and 120 healthy females with NACB-required characteristics (younger than 30 years, TSH between 0.5 and 2.0 mIU/L, normal thyroid ultrasound, absence of thyroid disease and absence of other autoimmune diseases) were studied. Sera were analyzed for TPOAbs concentration using five IMA methods applied in automated analyzers: Immulite 2000 XPi (IMM); Maglumi 2000 Plus (MAG); Kryptor Compact Plus (KRY); Phadia 250 (PHA) and Liaison XL (LIA).ResultsA statistically significant difference (p < 0.05) between medians in male and female groups was observed for PHA (2.6 and 3.1 IU/mL, respectively) but not for the other four methods. Scatter plots of TPOAbs values revealed a wide dispersion with very different coefficients of variation between the five methods, varying from 48.6 % for KRY in females to 126.3 % for MAG in females. The URLs differed in males and females according to the method: 28.7 and 29.0 IU/mL for IMM, 24.6 and 25.4 IU/mL for MAG, 6.4 and 6.9 IU/mL for KRY, 8.3 and 10.0 IU/mL for PHA and 14.2 and 17.9 IU/mL for LIA, respectively. Such URLs were lower than those stated by the manufacturers except for LIA in females. The difference between URLs ranged from a minimum of 11.3 % (LIA in males) to a maximum of 66.8 % (PHA in males).ConclusionsDifferences in URLs could result from the different coating preparations of the TPO antigen (purified native or recombinant) on solid phase, which affect the proper exposure of the immunodominant epitopes recognized by the polyclonal antibodies present in serum of patients with autoimmune thyroid disease (AITD). Based on these findings, we suggest to overcome the proposal of the NACB guidelines which recommend to involve a single group of young male subjects, and propose, instead, to utilize two distinct groups: one of males and one of females. This new proposal removes the apparent contrast of an all-male reference group for a disease (such as AITD) that affects mainly females. However, in spite of the harmonization among methods provided by the use of an international standard preparation, the wide dispersion of quantitative results still observed in this study suggests the need for further efforts to better understand the cause of these discrepancies, focusing on TPO antigen preparations as the possible source of variability among different assays.

BACKGROUND-AIMResults of laboratory investigations (especially if values fall in"grey-zone") have limited meaning on medical decisions, without reference intervals (RIs). The majority of medical laboratories adopt intervals (reccomended by manufacturers or by scientific literature) but take ensurance that they are proper for clinical use and compatible with its own population. Almost none of laboratories spend time and resources to establish reference intervals themselves due to dificulties in selection of reference group. We aimed to use a posteriori technique to calculate reference intervals from collected data using statistical techniques (robust method after eliminating outliers). METHODSData collection was exhaustive: all patients investigated in Central Medical Laboratory of Tirgu Mures, Romania, Emergency Hospital between 2010 and 2013 were included in the study. The data collected are values for biochemical (from COBAS 6000 and ARCHITECT platforms) and haematological parameters (from Sysmex and Cell Dyne analysers). The methodology involved data processing using sophisticated filters to eliminate outliers and complex statistical algorithms to calculate percentiles 2.5 and 97.5 and histogram plotting with cumulative percentages to derive the final reference intervals (indirect Hoffmann method).. RESULTSRobust linear regressions (biomedical parameter results vs cumulative percent) were obtained in order to find the best fitted linear segment of the curves, which contained reference intervals. 60-85 % of collected data could be used to obtain RIs. The obtained ranges were evaluated in comparison to the ranges indicated by reagent manufacturers and between different manufacturers. The reproducibility and acuracy of obtained RIs were in acceptable limits. A multicenter comparative evaluation of these intervals should be indicated to confirm the results. CONCLUSIONRobust "a posteriori" studies can be used to establish and to check transferred RIs. Indirect visual method -Hoffmann provides accurate/ reproducible RIs. Detection and elimination of outliers is not necessary (the variation of RIs values are insignificant). Supplimentary verifications are needed to check appropriately intervention in medical decisions. BACKGROUND-AIMAll the medical laboratories in Nepal are using the reference range of kit supplied in the reagents due to lack of local reference range. Establishment of reference range locally is important as analyzing the specimens. Reference interval is essential to make decision about the patient's condition. Reference range is affected by age, sex, diet, ethnicity, environment and genetics. This is the reason for each laboratory should have its own reference range for each test.This study was designed to establishes reference interval for outline biochemical analytes for the Nepalese adult population , a part of multicenter reference interval project being conducted around the world by the IFCC,C-RIDL. METHODSFrom six different regions, fasting venous blood was obtained from apparently healthy volu...