Analytical quality goals derived from the total deviation from patients' homeostatic set points, with a margin for analytical errors

Using the likelihood ratio to evaluate allowable total error – an example with glycated hemoglobin (HbA1c)

Allowable total error is derived in many ways, often from data on biological variation in normal individuals. We present a new principle for evaluating allowable total error: What are the diagnostic consequences of allowable total errors in terms of errors in likelihood ratio (LR)? Glycated hemoglobin A

We estimated a function for LR of HbA

Measuring HbA

These principles of evaluating allowable total error can be applied to any diagnostically used analyte where the distribution of the analyte’s concentration is known in patients with and without the disease in a clinically relevant population. In the example used, the allowable total error of 6% leads to very erroneous LRs, suggesting that the NGSP limits of ±6% are too liberal.