Can the prevalence of high blood drug concentrations in a population be estimated by analysing oral fluid? A study of tetrahydrocannabinol and amphetamine.
OBJECTIVE
To study several methods for estimating the prevalence of high blood concentrations of tetrahydrocannabinol and amphetamine in a population of drug users by analysing oral fluid (saliva).


METHODS
Five methods were compared, including simple calculation procedures dividing the drug concentrations in oral fluid by average or median oral fluid/blood (OF/B) drug concentration ratios or linear regression coefficients, and more complex Monte Carlo simulations. Populations of 311 cannabis users and 197 amphetamine users from the Rosita-2 Project were studied.


RESULTS
The results of a feasibility study suggested that the Monte Carlo simulations might give better accuracies than simple calculations if good data on OF/B ratios is available. If using only 20 randomly selected OF/B ratios, a Monte Carlo simulation gave the best accuracy but not the best precision. Dividing by the OF/B regression coefficient gave acceptable accuracy and precision, and was therefore the best method. None of the methods gave acceptable accuracy if the prevalence of high blood drug concentrations was less than 15%.


CONCLUSIONS
Dividing the drug concentration in oral fluid by the OF/B regression coefficient gave an acceptable estimation of high blood drug concentrations in a population, and may therefore give valuable additional information on possible drug impairment, e.g. in roadside surveys of drugs and driving. If good data on the distribution of OF/B ratios are available, a Monte Carlo simulation may give better accuracy.
Gjerde
Hallvard
H
Norwegian Institute of Public Health, Division of Forensic Toxicology and Drug Abuse, Oslo, Norway. Hallvard.Gjerde@fhi.no
Verstraete
Alain
A
D000661:Amphetamine / Q000032:analysis*; D001334:Automobile Driving / Q000331:legislation & jurisprudence; D000697:Central Nervous System Stimulants / Q000032:analysis*; D013759:Dronabinol / Q000032:analysis*; D005240:Feasibility Studies; D053593:Forensic Toxicology / Q000379:methods; D006801:Humans; D016014:Linear Models; D009010:Monte Carlo Method; D011619:Psychotropic Drugs / Q000032:analysis*; D012463:Saliva / Q000737:chemistry*; D015813:Substance Abuse Detection
D000697:Central Nervous System Stimulants; D011619:Psychotropic Drugs; D013759:Dronabinol; D000661:Amphetamine