Manufacturers have very strict codes of quality assurance if they are internationally accredited. Their manufacturing quality control steps are carefully monitored in a stepwise fashion. However, to produce a perfect product every time is impossible. Inter-batch variability does occur. In the end the manufacturer is in business to make a profit!

Monitoring can tell you about the batch to batch variability of tests during use. Markers for specificity, sensitivity or both can be included in testing protocols.

Monitoring within a laboratory is an important quality control measure and the use of external standards can show not only day to day variability but trends in assay performance.

The role of the National Reference Laboratory is to gather and collate these data to follow assay performances in a more general manner and to provide sufficient data to continually evaluate test performance and batch to batch variability.