Cut-off and Accuracy
Back- What is test Cut-off/cutoff?
- A cutoff, or cut-off, of a qualitative test method is the threshold level of the target substance that distinguishes positive and negative results. For example, if a urine amphetamine test has a cutoff of 300ng/ml, samples contain less than 300ng/ml amphetamine should test negative and samples contain more than 300ng/ml amphetamine should test positive. Our drug test pages list cut-off levels of each drug test.
- How is cut-off level related to test accuracy?
- Since the actual cutoff of a test is determined by the test components (reagents and procedure), the cutoff levels vary from manufacturer to manufacturer, and, often, batch to batch. Inaccuracy of cutoff level is a major cause of systematic error in rapid immunoassay tests. For example, if an amphetamine test kit claims having a cutoff level of 300ng/ml, but its actual cutoff is 500ng/ml, a urine sample containing 500ng/ml of amphetamine will test negative, or false negative.
- How to make sure your results are accurate?
- In order to make test results accurate, the first important matter is to select quality test products that have accurate cutoffs. When there is doubt, you can do several things. You can inquire from the manufacturer its test record of the same batch product you purchased. You can also test specimens with known (such as spiked) concentrations of the target substance. With quality test method, 50% above cutoff specimens should always test positive and 50% below cutoff specimens should always test negative. Another way is to test specimens and compare the results with those obtained by other trustworthy test methods. It is also important that the operator exactly follows the test instruction provided by the manufacturer.
The sensitivity cutoff levels of our Rapid test products are set precisely to highly accurate standard/control samples.
Back