AccuMeth® brand test kits have been validated by field testing and by independent laboratory analysis. The average deviation for the 0.1 legal limit kits in quantitative studies is 9.1% ; median is 6.5%. The average deviation for the 0.5 legal limit kits in quantitative studies is 9% ; median is 8%. Certified laboratories analyzing methamphetamine residue are allowed a deviation of + or - 20% on their surrogate recovery. Many of laboratories offering methamphetamine residue analysis have not been validated for meth analysis nor do they hold any meth related certifications.