Rapid Tests

Cut-off and Accuracy

What is a 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 often vary from manufacture to manufacture, and, some times, lot to lot. 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 400ng/ml, a urine sample containing 380ng/ml of amphetamine will test negative, or false negative.

How to make sure your results are accurate?

In order to get accurate test results, the first important 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 all Acro Biotech Rapid test products are set precisely to highly accurate standard/control samples.

Please feel free to contact our technical personnel to discuss test accuracy issues.