Methods for assessing the condition of keratinized structures, including hair, in particular methods to determine the condition of keratinized structures in relation to suitability for analysis of analytes of interest in a test sample, are presented. The methods comprise contacting the keratinized structure with a non-proteolytic reducing agent and an optional proteolytic agent. The methods further include inspection of the hair sample, or measurement of free protein eluted from the keratinized structure, after reduction and optional proteolysis to determine condition prior to analyte identification and quantitation by known techniques such as immunoassays.