Setting out to develop a novel assay can be a duanting task, especially for the first timer. It can be very confusing to know where to begin and to know which tests need to be run to verify the limits of detection, calibration, selectivity, stability, and the accuracy and precision of a particular assay. These are especially important parameters if the assay will eventually be used to support pre-clinical or clinical studies.
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Guidance for Industry - Bioanalytical Method Validation", published by the FDA is an excellent resource for systematically evaluating the various parameters of a qauntitative assay. The basic principles laid out in this document are applicable to a wide variety of assay formats including HPLC, LC/MS, ELISA, and even reporter assays or other cell based models.
Even if you are an experienced assay developer, reading the FDA guidelines can illuminate concepts you may instinctively know but have never fully articulated (or documented!)