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Reference Ranges and What They Mean

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What are decision limits?

For a small number of tests, long-term studies of certain disease processes have led to the establishment of decision limits that are more useful than reference ranges in determining clinical outcomes and guiding treatment decisions. Decision limits are values that represent either the upper or lower quantity of an analyte that are consistent with a disease state or indicate a need for treatment.

Blood glucose is an example of an analyte for which decision limits have been established and are widely used by healthcare providers. For adults in a routine setting in which fasting blood glucose testing is done to detect type 2 diabetes, a fasting glucose level of 126 mg/dL (7.0 mmol/L) or above, obtained on more than one testing occasion, indicates diabetes. Treatment is required to reduce the risk for cardiovascular disease, kidney disease, and other long-term complications of diabetes.

In this situation, it is a value above a particular limit that provides information rather than a value that falls within or outside a set range of numbers.

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