The Manufacturer Consumer Specification Dilemma

Below is a manufacturer specification for releasing a reagent for an assay.

It is an all or nothing approach, meaning that all reagents in the green are sold and have full value for the manufacturer, while all reagents out of spec (red line) are scrapped and have no value for the manufacturer. This is true for the two data points shown next to the arrow, one has full value, the other no value in spite of the fact that the data points have almost the same amount of error.

In the figure below is the consumer representation.

The blue line shows how patient harm is not an all or nothing approach but rather that patient harm increases with increasing error. For example, for a small glucose error in the hyperglycemic region, the insulin dose is slightly off. But a large glucose error (say a high hyperglycemic reading when truth is hypoglycemic) is life threatening.

This representation exists for many industries (say the fit of a car door, for example).

What’s the point?

In clinical chemistry, specifications from standard bodies (example glucose meter spec ISO 15197) use the manufacturer spec, not the consumer spec. But there are ways to express the consumer (laboratory) viewpoint, by using an error grid. For glucose meters, error grids exist but they are not part of ISO 15197.

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