Cutting edge confusion about cut-off settings in autoimmune diagnostics

In autoimmune diagnostics results are interpreted in relation to a single or multiple cut-off value(s) in order to decide if the test is negative, weak positive, positive, or even strong positive. The way a cut-off is established appears to be very heterogeneous and this hampers harmonization of test results obtained in assays, either established in-house or obtained from different companies. In this context it is surprising that in diagnostic and classification criteria for distinct autoimmune diseases referral is made to cut-off values with the intention of harmonization. In this review article distinct ways to establish cut-off values will be described and discussed in relation to some disease criteria in order to increase the awareness of the confusion matrix of cut-off values and, as a consequence, the implications for test result interpretation.