Table 4.
Diagnostic performance of oral fluid THC test in detecting a DEQ response of < 4 or ≥ 4 on question 1: Do you feel a drug effect right now? (PP2, N = 41)
| Before tests are not impaired; final tests (T = 4 h) are subjectively not impaired if DEQ < 4 | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| DEQ ≥ 4 | DEQ < 4 | Total | Sensitivity (95% CI) | Specificity (95% CI) | Accuracy (95% CI) | Percent false positive (95% CI) | Percent false negative (95% CI) | PPV (95% CI) | NPV (95% CI) | p value | |
| Oral fluid test is positive if THC ≥ 10 ng/ml | |||||||||||
| Oral fluid THC positive | 2 | 37 | 39 | 50.0 (6.7–93.2) | 52.6 (40.9–64.0) | 52.4 (41.1–63.6) | 47.4 (36.0–59.1) | 50.0 (6.8–93.2) | 5.1% (0.6–17.3) | 95.3% (84.2–99.4) | < 0.001 |
| Oral fluid THC negative | 2 | 41 | 43 | – | – | – | – | – | – | ||
| Total | 4 | 78 | 82 | – | – | – | – | – | – | ||
| Oral fluid test is positive if THC ≥ 25 ng/ml | |||||||||||
| Oral fluid THC positive | 0 | 25 | 25 | 0.0 (0.0–60.2) | 67.9 (56.4–78.1) | 64.6 (53.3–74.9) | 32.1 (21.9–43.6) | 100.0 (39.8–100.0) | 0.0% (0.0–13.7) | 93.0% (83.0–98.1) | < 0.001 |
| Oral fluid THC negative | 4 | 53 | 57 | – | – | – | – | – | – | ||
| Total | 4 | 78 | 82 | – | – | – | – | – | – | ||
McNemar’s chi-squared test was used to compare the difference in performance between the diagnostic test being evaluated and the comparison standard