Fentanyl Concentrations (ng/mL)   CB PB C:P Ratio N 166 166 166 Min 1.8 1.7 0.03 Max 176 373 2.43 Mean 20.18 21.16 1.23 Median 12.00 11.00 1.03     Standard Deviation 0.57 CB = Central Blood, PB = Peripheral Blood, C/P = Central/Peripheral Blood

Table 4: Summary of 166 fentanyl positive cases (13 cases removed).