This is in line with HTA guidance on use of residual clinical material and was approved by the Royal Devon and Exeter Pathology Governance Group. in comparison FAAP95 with the manufacturers recommended threshold inside a combined cohort of young-onset ( age 30) diabetes (UNITED study (Using pharmacogeNetics to Improve Treatment in Early-onset Diabetes), n=145). Results Using the manufacturers SR1001 limit of detection, 6 WHO U/mL, 16.2% of people in the control cohort experienced detectable levels of ZnT8A and those who experienced detectable ZnT8A were much more likely to be younger (p 0.0001). The 97.5th and 99th centile thresholds were substantially higher in more youthful participants: 18 and 127 WHO U/mL (tested less than 30 years) in comparison with 9 and 21 WHO U/mL (tested 30 years and over). In SR1001 the UNITED cohort some of those found to be ZnT8A-positive from the manufacturers threshold but bad using the appropriate 99% centile cut-off (127 WHO U/mL) displayed characteristics suggestive of type 2 diabetes. Conclusions Age-related thresholds are needed for ZnT8A screening. In those aged 30 years, use of manufacturers recommended cut-offs may result in low test specificity and potentially high rates of false positive test results in individuals who do not have autoimmune diabetes. subspecies paratuberculosis, which has been explained.16 Another probability for the higher titer and prevalence of ZnT8A in those tested 30 years in the control cohort is that there is a potential enrichment of individuals in the prodrome stage of T1D. However, the overall existence prevalence of T1D is definitely less than 0.3% (with approximately half of instances occurring after age 30)17 and therefore will be contributing only a very small amount to the difference between 30?and 30 cohorts (~0.15%). To our knowledge, this is one of the 1st studies to show age effects of ZnT8A on thresholds of positivity. A earlier study by Vermeulen em et al /em 7 reported using age-restricted cut-offs for positivity for his or her liquid-phase radiobinding assay to detect ZnT8A. Their SR1001 age cut-offs differed from ours (0C14 years and 15C39 years) and their control human population was considerably smaller (n=761), with only those aged up to 39 assessed. Due to the nature of the control cohort, the findings of this study are limited to one human population which is definitely mainly of Western descent. In addition, this study only used one assay type for SR1001 ZnT8A; however, the RSR ELISA is used by many medical laboratories since it was distributed and validated in 2013.18C20 Differences in ZnT8A prevalence have been reported in non-white ethnic individuals with diabetes; defining appropriate research ranges for different ethnicities and for additional assays will be important areas for future study.21 22 A further limitation is that although this is a large cohort, far in excess of what has been previously reported,9 19 23 the sample size is still insufficient to do more than visually assess an optimal age cut-off. Consequently, an even larger sample size would be needed to give greater detail on ideal test cut-offs for different age groups. High medical specificity of islet autoantibody checks is definitely of particular importance in the establishing of low prior prevalence, such as the case of prediction of T1D in the general human population or the analysis of autoimmune diabetes in older adults.17 By setting robust and well-defined cut-offs for each assay based on appropriate control populations, this will guarantee high assay specificity and SR1001 reduce potentially high rates of false positives in those with non-autoimmune diabetes. This is of increasing importance for studies into the prediction of T1D due to the recent progressions in treatment therapy study24 and in differentiating autoimmune from other forms of diabetes.25 We have demonstrated potential misclassification of diabetes types due to the use of manufacturers recommended cut-off. This is likely to impact earlier work where reported prevalence of ZnT8A offers varied and manufacturers recommendations of cut-offs have been used instead of a powerful population-defined threshold. Summary In those aged 30 years, a higher age-related threshold is likely to be needed for ZnT8A screening to prevent low test specificity and potentially high rates of false positive test results in individuals who do not have autoimmune diabetes. Acknowledgments We would like to say thanks to the UNITED study participants for his or her participation in the study. We would also like to say thanks to Dr Beverley Shields for her advice in relation to the statistical analysis. Footnotes Contributors: SLG, AC, AGJ and TJM conceived the idea and designed the study. AC and TJM collected the data. SLG analyzed the data with assistance from AC, AGJ and TJM. SLG drafted the manuscript with assistance from AGJ and TJM. All authors critically revised the manuscript and authorized the final version. TJM is the guarantor of this work and, as such, offers.