The minimum frequency for QC testing is the frequency defined by the manufacturer or the frequency defined by the regulatory agency that inspects your laboratory, whichever is more stringent. Other factors may cause the laboratory to decide to test controls more frequently. These factors include:
- the stability of the analyte and the method system
- the number of patient tests that are routinely performed
- change of instrument operators at change of work shift
- reagent change
Remember that if a problem is discovered, the samples in previous runs of the instrument may also have been affected. Once the problem(s) are corrected, it may be necessary to go back and re-run previous samples working in reverse order, until the retested results match the original results.