Functional groups, determination chromatography detection limits

The vahdity of assay results is best proved by tests for parallelism of the response curves for both calibrators and randomly selected samples from male and female subjects of various ages. In addition, comparison of extraction/ chromatography immunoassays should be validated by comparison with mass spectrometry methods. Direct immunoassays should not be used for female and prepubertal subjects, especially infants. These groups should be tested using an extraction immunoassay or an LC-MS/MS assay. It is important to note that both types of direct immunoassay demonstrate problems with functional sensitivity for low concentrations. Each lab should determine the low-end detection limit of their assay despite manufacturer claims. 

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