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Table 3 Estimated Regression Coefficients (β) and 95% Confidence Intervals (CI) in Adjusted and Unadjusted Linear Regression Models of the Log-transformed Blood THC (ng/ml) on Log-transformed Oral Fluid THC (ng/ml) among Drivers with Non-zero THC Concentrations in either Blood or Oral Fluid, Continental United States, Nighttime Weekend and Daytime Friday, 2013–2014

From: Validity of oral fluid test for Delta-9-tetrahydrocannabinol in drivers using the 2013 National Roadside Survey Data

  Model 1 (n = 500) Model 2 (n = 478) Model 3 (n = 472)
β (95%CI) β (95%CI) β (95%CI)
Intercept 0.14 (0.01, 0.26) 0.00 (−0.17, 0.17) −0.01 (−0.31, 0.28)
Log of Oral Fluid THC Concentration (ng/ml) 0.25 (0.22, 0.29) 0.25 (0.21, 0.29) 0.25 (0.22, 0.29)
Blood Alcohol Concentration (ng/dl)
 0   Ref Ref
 1–39   − 0.29 (− 0.77, 0.19) − 0.22 (− 0.72, 0.28)
 40+   − 0.18 (− 0.60, 0.25) − 0.15 (− 0.58, 0.27)
Last time use of Marijuana
 Over a year/Never   Ref Ref
 Over a Month   0.15 (−0.13, 0.42) 0.16 (−0.12, 0.44)
 Past 2 days to a month   0.22 (−0.01, 0.45) 0.22 (−0.01, 0.46)
 Past 24 Hours   0.29 (0.08, 0.49) 0.30 (0.10, 0.51)
Age (years)
 16–20    Ref
 21–34    0.05 (−0.17, 0.27)
 35–54    0.06 (−0.20, 0.33)
  ≥ 55    −0.13 (− 0.56, 0.30)
Gender (Male vs. Female)    −0.12 (− 0.29, 0.06)
Race
 Black    Ref
 White    −0.03 (−0.21, 0.15)
 Other Race    0.27 (0.01, 0.52)
R2 0.29 0.30 0.31