Geometric Classification of Scalp Hair for Valid Drug Testing, More Reliable Than Hair Curl Groups

The study evaluated the reliability of a geometric classification system for scalp hair, finding that a 6-group method was more reliable than the previously used 8 hair curl groups. Despite the study's small size, it highlighted the need for a reliable and objective classification of human hair curl, especially as hair is increasingly used as a substrate for testing treatment compliance in medicine. The study suggested that a digital classification system could further reduce operator error.