Limit of quantitation (LoQ)

Limit of quantitation is the smallest quantity value that meets the requirements for intended use.

There is no set procedure to determine the limit of quantitation. Some authors suggest setting separate goals for bias and imprecision. Others such as Westgard use a model to combine the bias and imprecision into "total error" and compare it to a total allowable error goal. Others prefer to avoid the use of models and estimate total error directly using difference between the results of a method and a reference method (Krouwer, 2002). In other areas such as immunoassays the limit of quantitation is often defined as functional sensitivity where the precision profile function CV is equal 20%.