Internal quality control is set up within a laboratory to monitor and ensure the reliability of test results from that laboratory.

The primary tool for internal quality control is called a control. A control is a specimen with a predetermined range of result values, called control values, that is processed in the same manner as a patient sample. Control samples are processed with each series or run of patient samples.

If the result of a test on a control sample is different from its known value, this indicates a problem in the equipment or the methods being used.