How Are QC Results Used?

Use QC results to validate patient results. After the validation of QC results, use patient results for diagnosis, prognosis, or treatment planning. For example, when testing a patient's serum for potassium, the test result shows how much potassium (what concentration) is present in the blood. The physician uses this result to determine whether the patient has a low, normal, or high potassium level.

For example, if the measured value of potassium in a patient's serum is 2.8 mmol/L (a unit of measure, millimoles per liter), this result is abnormally low and indicates an inappropriate loss of potassium.

What indicates this test is truly reliable? Perhaps the instrument is out of calibration and the patient's true potassium value is 4.2 mmol/L, which is a normal result.

Resolve the question of reliability for most testing by regular testing of quality control materials and the application of statistical process control values.

Test QC materials and develop a database of values to calculate a mean and range (for example, the mean ±3SD). Compare the QC results to the range using statistical process control (SPC) rules and make decisions to accept or reject patient results based on the outcome of the rule evaluation.