Look, I found this article where they sent hair from the same person to different labs and got MASSIVELY different results.
Reliability on Intra-Laboratory and Inter-Laboratory Data of Hair Mineral Analysis Comparing with Blood Analysis
Nowadays, although its clinical value remains controversial institutions utilize hair mineral analysis. Arguments about the reliability of hair mineral analysis persist, and there have been evaluations of commercial laboratories performing hair mineral ...
www.ncbi.nlm.nih.gov