Quality may be assessed at different points in time. Broadly, assessments may be made before or after the kit is sold.

Pre-market-(before tests can be sold to the laboratories and therefore before the assay is used)

To assess the performance of an assay or batch of a kit before release. The initial and formal evaluation of an assay performance is usually a "once off" assessment at a single point in time. Usually only one or two batches are examined.

Batch testing may be employed to evaluate all subsequent batches for all assays by using characterised panels eg seroconversion samples. The assay or batch must pass a set criteria before release onto the market

Post market-(laboratories are using the assay)

This is referred to as ongoing performance monitoring.