Interference commercial assay kits, specificity

The preferred tracer in commercially available RIA kits for labeled testosterone is I. The size of the iodinated group and the site of linkage may greatly affect assay affinity and specificity. Some methods use solvent extraction or chromatography, or both, to remove interferences from other steroids and some drugs. These prefiminaiy steps also permit concentration of the sample when low concentrations of testosterone are expected. Like automated assays, manual RIA assays perform better at higher concentrations, with questionable utility in female and prepubertal subjects. ... 

In summary, rapid tests, either immunoassay or enzymatic formats, are the methods of choice when qualitative or semi-quantitative results are required within a short timescale, specifically, around 30 min for targeted residue screening. In general, these assay formats are portable (suitable for in situ testing) and simple to both operate and interpret. A wide variety of test formats are commercially available, many of which are applicable for the detection of classes of antibiotics, such as P-lactams and tetracyclines with detection capabilities at or below the appropriate RLs. As with other test kits, it is important to determine the applicability of the assay for the specific matrix type prior to use as certain matrices are known to contain interference that causes elevated false non-compliant/compliant rates. 

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