Alternate Matrices: Analysis of Initial Test Results for Cannabinoids and Opiates

1. Alternate Matrices: Analysis of Initial Test Results for Cannabinoids and Opiates John M. Mitchell, Ph.D. Drug Testing Advisory Board March 11, 2003

2. Bayesian Analysis of Immunoassay Results Utilizes the Number of True Positives, True Negatives, False Positives and False Negatives to determine four parameters: Sensitivity Specificity Positive Predictive Value (PPV) and Negative Predictive Value (NPV)

3. Definitions True positive- A sample containing drug analyte(s) at concentration(s) equal to or greater than the defined cutoff. True negative- A sample containing drug analyte(s) at concentration(s) less than the defined cutoff. False positive- A sample containing drug analyte(s) at concentration(s) less than the defined cutoff (or no drug at all) but identified as positive. False negative- A sample containing drug analyte(s) at concentration(s) equal to or greater than the defined cutoff but identified as negative

4. Sensitivity Sensitivity = _____True Positives_________ True Positives + False Negatives Multiply this value by 100 to obtain the percent of the true positives identified Multiply this value by 100 to obtain the percent of the true positives identified

5. Specificity Specificity = _____True Negatives_________ True Negatives + False Positives Multiply this value by 100 to obtain the percent of the true negatives that were identified.Multiply this value by 100 to obtain the percent of the true negatives that were identified.

6. Positive Predictive Value (PPV) PPV = _____True Positives_________ True Positives + False Positives Multiply (1-specificity) by 100 to obtain the false positive rateMultiply (1-specificity) by 100 to obtain the false positive rate

7. Negative Predictive Value (NPV) NPV = _____True Negatives_________ True Negatives + False Negatives

8. Analysis of EMIT Results for THCA in Urine; PT Occasion 61 & 62 3 False positives due to presence of Glutaraldehyde Sensitivity is 1.00 because all of the true positives were identified. Specificity is 0.99 because ~ 1% of the true positives were identified as false positives PPV is 0.98 because 3 of the identified positives were false positives NPV is 1.00 because it reflects the true neg/(true neg+false neg) and there were no false negatives3 False positives due to presence of Glutaraldehyde Sensitivity is 1.00 because all of the true positives were identified. Specificity is 0.99 because ~ 1% of the true positives were identified as false positives PPV is 0.98 because 3 of the identified positives were false positives NPV is 1.00 because it reflects the true neg/(true neg+false neg) and there were no false negatives

9. Analysis of FPIA Results for Opiates in Urine; PT Occasion 61 & 62

10. Results of Initial Tests For Cannabinoids in Urine; PT Occasion 61 & 62 3 false positive probably the result of the presence of glutaraldehyde3 false positive probably the result of the presence of glutaraldehyde

11. Analysis of Results from Initial Tests for Cannabinoids in Urine; PT Occasion 61 & 62 All parameters .98 or betterAll parameters .98 or better

12. Results of Initial Tests For Opiates in Urine; PT Occasion 61 & 62

13. Analysis of Results from Initial Tests for Opiates in Urine; PT Occasion 61 & 62 All parameters 0.86 or higher.All parameters 0.86 or higher.

14. Cannabinoids and Opiates in Hair PT Cycles 1-4 Cutoffs for analysis THCA Initial Test- 1 pg/mg; Confirmation- 0.05 pg/mg Opiates Initial and Confirmation Tests – 200 pg/mg

15. Analysis of Initial Tests For Cannabinoids in Hair THCA- True positives samples with THCA> 0.05 THC True positives samples with THC > 1.0 Cannabinoids True positives samples with THCA > 0.05 or THC > 1.0 Bolded values: Arbitrarily set 0.8 or greater as an index of performance. Sensitivity- 80% of true positive identified Specificity – 80% of true negatives identified THCA- True positives samples with THCA> 0.05 THC True positives samples with THC > 1.0 Cannabinoids True positives samples with THCA > 0.05 or THC > 1.0 Bolded values: Arbitrarily set 0.8 or greater as an index of performance. Sensitivity- 80% of true positive identified Specificity – 80% of true negatives identified

16. Analysis of Initial Tests For Cannabinoids in Hair Bolded values are 0.8 or greater PPV- 80% of the positives identified were true positives NPV- 80% of the negatives identified were true negativesBolded values are 0.8 or greater PPV- 80% of the positives identified were true positives NPV- 80% of the negatives identified were true negatives

17. Analysis of Initial Tests For Opiates in Hair Question? How could EMIT have such high values for Specificity? This reflects that it identified the true negativesQuestion? How could EMIT have such high values for Specificity? This reflects that it identified the true negatives

18. Analysis of Initial Tests For Opiates in Hair Question: How could EMIT rate so low for sensitivity and so high for PPV. Sensitivity reflect the fraction of true positives that are identified. PPV reflect the percent of the identified positives that are true positives. There fore if itit only identified 40% of the true positives and had no false positives the PPV would be high. Data MOR TP= 7 TN= 65 FP =0 FN =8 COD TP= 5 TN= 67 FP= 1 FN = 6 6-AM TP= 6 TN= 66 FP= 1 FN =7 Question: How could EMIT rate so low for sensitivity and so high for PPV. Sensitivity reflect the fraction of true positives that are identified. PPV reflect the percent of the identified positives that are true positives. There fore if itit only identified 40% of the true positives and had no false positives the PPV would be high. Data MOR TP= 7 TN= 65 FP =0 FN =8 COD TP= 5 TN= 67 FP= 1 FN = 6 6-AM TP= 6 TN= 66 FP= 1 FN =7

19. Cannabinoids and Opiates in Oral Fuids PT Cycles 1-3 Neat Oral Fluids Cutoffs for analysis THCA Initial Test- 4 ng/mL Confirmation- 2 ng/mL Opiates Initial and Confirmation Tests – 40 ng/mL

20. Analysis of Initial Tests For THC in Oral Fluids Question How could ELISA 1 and EIA have such low sensitivity and all other parameter be high. Sensitivity tells us that few true positives were identified at the prescribed cutoff. Specificity tells us that the all true negatives were identified. PPV tell us that all of the identified positives were true positives NPV reflects the False negative results . It would appear that the tests had a higher cutoff than 4 ng/mLQuestion How could ELISA 1 and EIA have such low sensitivity and all other parameter be high. Sensitivity tells us that few true positives were identified at the prescribed cutoff. Specificity tells us that the all true negatives were identified. PPV tell us that all of the identified positives were true positives NPV reflects the False negative results . It would appear that the tests had a higher cutoff than 4 ng/mL

21. Analysis of Initial Tests For Opiates in Oral Fluids

22. Analysis of Initial Tests For Opiates in Oral Fluids How could assays have high Sensitivity and Low PPV’s? Sensitivity reflects the portion of the true positives identified. PPV reflect the portion of the positives that were true positives. This would mean that there were a number of false positives. DataHow could assays have high Sensitivity and Low PPV’s? Sensitivity reflects the portion of the true positives identified. PPV reflect the portion of the positives that were true positives. This would mean that there were a number of false positives. Data