Table 2 Proposed discrimination criteria (cut-off or elevation threshold) for GHB and its tested biomarkers, number of respective true positives (TP), false positives (FP), true negatives (TN), false negatives (FN), and their calculated specificity (spec, (TN/TN + FP)), sensitivity (sens, (TP/(TP + FN)), and the positive predictive value (PPV = TP/(TP + FP)) from study cohort II at 4.5 h, 11 h and 28 h following placebo or GHB intake.
Analyte | Discrimination criteria | TN | FP | TP | FN | Spec | Sens | PPV | TN | FP | TP | FN | Spec | Sens | PPV | TN | FP | TP | FN | Spec | Sens | PPV |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
4.5 h | 11 h | 28 h | ||||||||||||||||||||
GHB | Strategy a: Cut-off (6 µg/mL) | 40 | 0 | 40 | 0 | 1.0 | 1.0 | 1.0 | 35 | 0 | 5 | 32 | 1.0 | 0.1 | 1.0 | 34 | 0 | 2 | 36 | 1.0 | 0.1 | 1.0 |
Strategy a: Cut-off (10 µg/mL) | 40 | 0 | 39 | 1 | 1.0 | 1.0 | 1.0 | 35 | 0 | 3 | 34 | 1.0 | 0.1 | 1.0 | 34 | 0 | 0 | 35 | 1.0 | 0.0 | ||
Strategy c: Ratio urine1/urine2 (> 5) | 35 | 4 | 39 | 0 | 0.9 | 1.0 | 0.9 | 35 | 4 | 11 | 24 | 0.9 | 0.3 | 0.7 | 35 | 4 | 2 | 31 | 0.9 | 0.1 | 0.3 | |
GHB-carnitine | Strategy a: Cut-off 1 (1 µg/mL) | 40 | 0 | 34 | 6 | 1.0 | 0.9 | 1.0 | 34 | 1 | 0 | 37 | 1.0 | 0.0 | 0.0 | 34 | 0 | 2 | 36 | 1.0 | 0.1 | 1.0 |
Strategy c: Ratio urine1/urine2 (> 5) | 35 | 4 | 36 | 3 | 0.9 | 0.9 | 0.9 | 35 | 4 | 3 | 32 | 0.9 | 0.1 | 0.4 | 35 | 4 | 2 | 31 | 0.9 | 0.1 | 0.3 | |
GHB-glycine | Strategy a: Cut-off (1 µg/mL) | 40 | 0 | 40 | 0 | 1.0 | 1.0 | 1.0 | 35 | 0 | 13 | 24 | 1.0 | 0.4 | 1.0 | 33 | 1 | 3 | 31 | 1.0 | 0.1 | 0.8 |
Strategy b: MR (> 2.5) | 27 | 9 | 0 | 40 | 0.8 | 0.0 | 0.0 | 31 | 2 | 10 | 24 | 0.9 | 0.3 | 0.8 | 26 | 3 | 11 | 22 | 0.9 | 0.3 | 0.8 | |
Strategy c: Ratio urine1/urine2 (> 5) | 33 | 6 | 39 | 0 | 0.8 | 1.0 | 0.9 | 33 | 6 | 19 | 16 | 0.8 | 0.5 | 0.8 | 33 | 6 | 18 | 15 | 0.8 | 0.5 | 0.8 | |
GHB-glutamate | Strategy a: Cut-off (1.5 µg/mL) | 40 | 0 | 35 | 5 | 1.0 | 0.9 | 1.0 | 35 | 0 | 0 | 37 | 1.0 | 0.0 | 34 | 0 | 0 | 35 | 1.0 | 0.0 | ||
Strategy c: Ratio urine1/urine2 (> 5) | 32 | 7 | 37 | 2 | 0.8 | 0.9 | 0.8 | 32 | 7 | 10 | 25 | 0.8 | 0.3 | 0.6 | 32 | 7 | 9 | 24 | 0.8 | 0.3 | 0.6 | |
GHB-phenylalanine | Strategy a: Cut-off (0.0025 µg/mL) | 40 | 0 | 40 | 0 | 1.0 | 1.0 | 1.0 | 35 | 0 | 7 | 30 | 1.0 | 0.2 | 1.0 | 34 | 0 | 0 | 35 | 1.0 | 0.0 | |
Strategy c: Ratio urine1/urine2 (> 5) | 30 | 9 | 39 | 0 | 0.8 | 1.0 | 0.8 | 30 | 9 | 19 | 16 | 0.8 | 0.5 | 0.7 | 30 | 9 | 15 | 18 | 0.8 | 0.5 | 0.6 | |
GHB-taurine | Strategy a: Cut-off (0.05 µg/mL) | 40 | 0 | 37 | 3 | 1.0 | 0.9 | 1.0 | 35 | 0 | 4 | 33 | 1.0 | 0.1 | 1.0 | 34 | 0 | 0 | 35 | 1.0 | 0.0 | |
Strategy c: Ratio urine1/urine2 (> 5) | 38 | 1 | 39 | 0 | 1.0 | 1.0 | 1.0 | 38 | 1 | 17 | 18 | 1.0 | 0.5 | 0.9 | 38 | 1 | 14 | 19 | 1.0 | 0.4 | 0.9 | |
GHB-pentose | Strategy c: Ratio urine1/urine2 (> 5) | 36 | 3 | 39 | 0 | 0.9 | 1.0 | 0.9 | 36 | 3 | 31 | 4 | 0.9 | 0.9 | 0.9 | 36 | 3 | 31 | 2 | 0.9 | 0.9 | 0.9 |
GHB-glucuronide | Strategy a: Cut-off (3 µg/mL) | 40 | 0 | 0 | 40 | 1.0 | 0.0 | 35 | 0 | 0 | 37 | 1.0 | 0.0 | 34 | 0 | 0 | 35 | 1.0 | 0.0 | |||
Strategy c: Ratio urine1/urine2 (> 5) | 39 | 0 | 3 | 36 | 1.0 | 0.1 | 1.0 | 39 | 0 | 3 | 32 | 1.0 | 0.1 | 1.0 | 39 | 0 | 1 | 32 | 1.0 | 0.0 | 1.0 | |
GHB-sulfate | Strategy c: Ratio urine1/urine2 (> 5) | 39 | 0 | 5 | 34 | 1.0 | 0.1 | 1.0 | 39 | 0 | 5 | 30 | 1.0 | 0.1 | 1.0 | 39 | 0 | 7 | 26 | 1.0 | 0.2 | 1.0 |
U3 | Strategy c: Ratio urine1/urine2 (> 5) | 38 | 1 | 9 | 29 | 1.0 | 0.2 | 0.9 | 38 | 1 | 3 | 32 | 1.0 | 0.1 | 0.8 | 38 | 1 | 3 | 30 | 1.0 | 0.1 | 0.8 |
U4 | Strategy c: Ratio urine1/urine2 (> 5) | 39 | 0 | 24 | 15 | 1.0 | 0.6 | 1.0 | 39 | 0 | 12 | 23 | 1.0 | 0.3 | 1.0 | 39 | 0 | 9 | 24 | 1.0 | 0.3 | 1.0 |
U16 | Strategy c: Ratio urine1/urine2 (> 5) | 39 | 0 | 22 | 17 | 1.0 | 0.6 | 1.0 | 39 | 0 | 9 | 25 | 1.0 | 0.3 | 1.0 | 39 | 0 | 5 | 28 | 1.0 | 0.2 | 1.0 |
2,4-DHB | Strategy a: Cut-off 1 (25 µg/mL) | 40 | 0 | 12 | 28 | 1.0 | 0.3 | 1.0 | 35 | 0 | 2 | 35 | 1.0 | 0.1 | 1.0 | 34 | 0 | 1 | 34 | 1.0 | 0.0 | 1.0 |
Strategy a: Cut-off (36 µg/mL) | 40 | 0 | 7 | 33 | 1.0 | 0.2 | 1.0 | 34 | 0 | 0 | 37 | 1.0 | 0.0 | 34 | 0 | 0 | 35 | 1.0 | 0.0 | |||
Strategy c: Ratio urine1/urine2 (> 5) | 38 | 1 | 19 | 20 | 1.0 | 0.5 | 1.0 | 38 | 1 | 7 | 28 | 1.0 | 0.2 | 0.9 | 38 | 1 | 5 | 28 | 1.0 | 0.2 | 0.8 | |
3,4-DHB | Strategy a: Cut-off (40 µg/mL) | 39 | 1 | 32 | 8 | 1.0 | 0.8 | 1.0 | 35 | 0 | 5 | 32 | 1.0 | 0.1 | 1.0 | 34 | 0 | 1 | 34 | 1.0 | 0.0 | 1.0 |
Strategy a: Cut-off (120 µg/mL) | 40 | 0 | 32 | 8 | 1.0 | 0.8 | 1.0 | 35 | 0 | 5 | 32 | 1.0 | 0.1 | 1.0 | 34 | 0 | 1 | 34 | 1.0 | 0.0 | 1.0 | |
Strategy c: Ratio urine1/urine2 (> 5) | 39 | 0 | 33 | 6 | 1.0 | 0.8 | 1.0 | 39 | 0 | 8 | 27 | 1.0 | 0.2 | 1.0 | 39 | 0 | 4 | 29 | 1.0 | 0.1 | 1.0 | |
GA | Strategy a: Cut-off (160 µg/mL) | 40 | 0 | 17 | 23 | 1.0 | 0.4 | 1.0 | 35 | 0 | 0 | 37 | 1.0 | 0.0 | 34 | 0 | 0 | 35 | 1.0 | 0.0 | ||
Strategy a: Cut-off (400 µg/mL) | 40 | 0 | 17 | 23 | 1.0 | 0.4 | 1.0 | 35 | 0 | 0 | 37 | 1.0 | 0.0 | 34 | 0 | 0 | 35 | 1.0 | 0.0 | |||
Strategy c: Ratio urine1/urine2 (> 5) | 39 | 0 | 24 | 15 | 1.0 | 0.6 | 1.0 | 39 | 0 | 3 | 32 | 1.0 | 0.1 | 1.0 | 39 | 0 | 1 | 32 | 1.0 | 0.0 | 1.0 | |
GA-taurine | Strategy c: Ratio urine1/urine2 (> 5) | 39 | 0 | 21 | 18 | 1.0 | 0.5 | 1.0 | 39 | 0 | 4 | 31 | 1.0 | 0.1 | 1.0 | 39 | 0 | 2 | 30 | 1.0 | 0.1 | 1.0 |
SA | Strategy a: Cut-off (30 µg/mL) | 40 | 0 | 3 | 37 | 1.0 | 0.1 | 1.0 | 35 | 0 | 0 | 37 | 1.0 | 0.0 | 33 | 1 | 0 | 35 | 1.0 | 0.0 | 0.0 | |
Strategy a: Cut-off (60 µg/mL) | 40 | 0 | 0 | 40 | 1.0 | 0.0 | 35 | 0 | 0 | 37 | 1.0 | 0.0 | 34 | 0 | 0 | 35 | 1.0 | 0.0 | ||||
Strategy c: Ratio urine1/urine2 (> 5) | 38 | 1 | 1 | 38 | 1.0 | 0.0 | 0.5 | 38 | 1 | 2 | 33 | 1.0 | 0.1 | 0.7 | 38 | 1 | 4 | 29 | 1.0 | 0.1 | 0.8 | |
Succinylcarnitine | Strategy a: Cut-off (25 µg/mL) | 40 | 0 | 0 | 40 | 1.0 | 0.0 | 35 | 0 | 0 | 37 | 1.0 | 0.0 | 34 | 0 | 2 | 36 | 1.0 | 0.1 | 1.0 | ||
Strategy c: Ratio urine1/urine2 (> 5) | 39 | 0 | 1 | 38 | 1.0 | 0.0 | 1.0 | 39 | 0 | 2 | 33 | 1.0 | 0.1 | 1.0 | 39 | 0 | 7 | 26 | 1.0 | 0.2 | 1.0 | |
