TL19: Measuring Interval
*Vicki Petrides, Abbott Diagnostics 


The terms measuring interval, reportable range and analytical measuring range have all been used to describe the values that can be quantified and reported by an in vitro diagnostic test. The concepts may seem straightforward, but there is debate about which studies should be used for manufacturers to establish and laboratories to verify a measuring interval. Traditionally the limit of quantitation (LoQ), linearity, precision and method comparison data serve as the key studies to establish a measuring interval. One question for developers is, how close to the limits of the measuring interval do the samples tested need to be in order to support the claim? Another challenge in meeting the current expectations is that the current consensus guidance on linearity, CLSI EP6-A, suggests testing samples 20 – 30% above the desired measuring interval. While manufacturers may follow this advice, one could argue that doing so does not make sense as by definition, the assay cannot accurately quantify above the upper limit of the measuring interval. An additional question that often arises is what evidence is necessary to support a claim for a new product with a desired measuring interval that is larger than that of the predicate device? Should new products be limited by the upper limit of the predicate’s measuring interval? Please join us in discussing these questions as we hear the perspectives of FDA, industry and laboratory speakers.