Finding a prescribed drug in hair and estimating its daily dose are separate analytical questions. A study by Ferrari and colleagues compared hair results with reported medication use in 93 patients receiving ongoing treatment for primary headaches.
Detection and dose agreement were different outcomes
The team used liquid chromatography–tandem mass spectrometry to analyze hair samples and compared the findings with each participant’s medication history. The panel covered 23 drugs, and all 23 were detected somewhere in the study samples. Agreement between a reported drug and its detection was strong for most analytes. A statistically significant relationship between reported dose and hair level was found for only six drugs, including delorazepam and lorazepam.
Why a group association cannot recover one dose
A statistical relationship across a study group leaves uncertainty when applied to an individual. The paper compared hair concentrations with reported intake. It did not validate a conversion from a person’s hair result to a day-by-day dosing history or establish that a particular dose was missed.
In a disputed case, identify the sampled segment, its orientation, the method’s reporting criteria and the relevant medication records. Use the hair result for the question it can address, such as whether the drug was detected in the segment. Exact daily doses and the timing of a particular ingestion require other evidence.
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