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

Sensitivity reflects the portion of the true
positive samples that have been identified as
positive.
(1- Sensitivity) - reflects the portion of the
true positive samples that have been identified
as negative (False Negatives).
5
Specificity

• Specificity

• _____True Negatives_________
• True Negatives False Positives

Specificity reflects the portion of the true
negative samples that have been identified as
negative.
(1- Specificity) - reflects the portion of the
true negative samples that have been identified
as positive (False Positives).
6
Positive Predictive Value (PPV)

• PPV

• _____True Positives_________
• True Positives False Positives

PPV reflects that portion of the identified
positives that are true positives.
(1- PPV) - reflects that portion of the
identified positives that are false positives.
7
Negative Predictive Value (NPV)

• NPV

• _____True Negatives_________
• True Negatives False Negatives

NPV reflects that portion of the identified
negative samples that are true negatives.
(1- NPV) - reflects that portion of the
identified negative samples that are false
negatives.
8
Analysis of EMIT Results for THCA in Urine PT
Occasion 61 62
3 False positives due to presence of
Glutaraldehyde
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
MPT Occasion 61-62 Cutoffs IT 50 ng/mL
Confirm 15 ng/mL)
11
Analysis of Results from Initial Tests for
Cannabinoids in Urine PT Occasion 61 62
MPT Occasion 61-62 Cutoffs IT 50 ng/mL
Confirm 15 ng/mL)
12
Results of Initial Tests For Opiates in Urine PT
Occasion 61 62
MPT Occasion 61-62 Cutoffs IT Confirm 2000
ng/mL
13
Analysis of Results from Initial Tests for
Opiates in Urine PT Occasion 61 62
MPT Occasion 61-62 Cutoffs IT Confirm 2000
ng/mL
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
Cutoffs IT 1 pg/mg Confirm 0.05 pg/mg
16
Analysis of Initial Tests For Cannabinoids in Hair
Cutoffs IT 1 pg/mg Confirm 0.05 pg/mg
17
Analysis of Initial Tests For Opiates in Hair
Cutoffs IT Confirm 200 pg/mg
18
Analysis of Initial Tests For Opiates in Hair
Cutoffs IT Confirm 200 pg/mg
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
Cutoffs IT 4 ng/mL Confirm 2 ng/mL
21
Analysis of Initial Tests For Opiates in Oral
Fluids
Cutoffs IT Confirm 40 ng/mL
22
Analysis of Initial Tests For Opiates in Oral
Fluids
Cutoffs IT Confirm 40 ng/mL