Skip to main content

Table 1 Percentages of Drivers with THC Positivity in Blood and Oral Fluid and Sensitivity-Specificity Analysis of the Oral Fluid Test using the Blood Test as the Reference Criterion. The Analyses were performed for All Drivers and Stratified by Driver’s Characteristics

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

  N Positivity in blood THC N (%) Positivity in oral fluid THC
N (%)
Sensitivity %
(95% CI)
Specificity %
(95% CI)
All 4596 431 (9.4) 411 (8.9) 79.4 (75.2, 83.1) 98.3 (97.9, 98.7)
Age (years)
 16–20 479 76 (15.9) 75 (15.7) 81.6 (71.0, 89.6) 96.8 (94.6, 98.3)
 21–34 1909 241 (12.6) 233 (12.2) 80.1 (74.5, 84.9) 97.6 (96.8, 98.3)
 35–54 1491 92 (6.2) 88 (5.9) 81.5 (72.1, 88.9) 99.1 (98.4, 99.5)
  ≥ 55 717 22 (3.1) 15 (2.1) 54.6 (32.2, 75.6) 99.6 (98.7, 99.9)
Gender a
 Female 1980 143 (7.2) 128 (6.5) 74.1 (66.1, 81.1) 98.8 (98.2, 99.3)
 Male 2597 282 (10.9) 279 (10.7) 82.3 (77.3, 86.5) 98.0 (97.3, 98.5)
Race
 White 2718 186 (6.8) 173 (6.4) 74.7 (67.9, 80.8) 98.7 (98.1, 99.1)
 Black 1015 181 (17.8) 182 (17.9) 86.7 (80.9, 91.3) 97.0 (95.6, 98.0)
 Other 863 64 (7.4) 56 (6.5) 71.9 (59.2, 82.4) 98.8 (97.7, 99.4)
Last time use of marijuana b
 Beyond a year/Never 3651 106 (2.9) 107 (2.9) 72.6 (63.1, 80.9) 99.2 (98.8, 99.4)
 Over a month 294 51 (17.3) 50 (17.0) 84.3 (71.4, 93.0) 97.1 (94.2, 98.8)
 Past month/2 days 279 98 (35.1) 87 (31.2) 77.6 (68.0, 85.4) 93.9 (89.4, 96.9)
 Past 24 h 209 158 (75.6) 148 (70.8) 82.9 (76.1, 88.4) 66.7 (52.1, 79.2)
Blood alcohol concentration (ng/dl)
 0 4485 405 (9.0) 379 (8.5) 78.3 (73.9, 82.2) 98.5 (98.1, 98.8)
 1–39 34 12 (35.3) 14 (41.2) 100.0 (73.5, 100) 90.9 (70.8, 98.9)
 40+ 77 14 (18.2) 18 (23.4) 92.9 (66.1, 99.8) 92.1 (82.4, 97.4)
  1. a 19 missing data on sex
  2. b 163 missing data on last time use of marijuana