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The Atellica™ CH Phencyclidine (Pcp) assay is for in vitro diagnostic use in the qualitative or semiquantitative analyses of phencyclidine in human urine using the Atellica CH Analyzer, using a cutoff of 25 ng/mL. The Pcp assay provides only a preliminary analytical test result. A more specific alternative chemical method must be used to obtain a confirmed analytical result. Gas chromatography/mass spectrometry (OC/MS) is the preferred confirmatory method. The semi-quantitative mode is for purposes of enabling laboratories to determine an appropriate dilution of the specimen for confirmation by a confirmatory method such as Gas Chromatography/ Mass Spectrometty (GC-MS) or Liquid Chromatography/ Tandem Mass Spectrometry (LC-MS/MS) or permitting laboratories to establish quality control procedures. Clinical consideration and professional judgment should be applied to any drug-of-abuse test result, particularly when preliminary positive results are used.

The Atellica CH Pcp assay is a homogenous enzyme immunoassay based on competition between drug in the specimen and drug labeled with glucose-6-phosphate dehydrogenase (G6PDH) for antibody binding sites. G6PDH activity decreases upon binding to the antibody, so the drug concentration in the specimen can be measured in terms of enzyme activity. Active enzyme converts nicotinamide adenine dinucleotide (NAD+) to NADH in the presence of glucose-6-phosphate (G6P), resulting in an absorbance change that is measured spectrophotometrically at 340/410 nm.

Here's a breakdown of the acceptance criteria and the study that proves the device meets them, based on the provided text:

Acceptance Criteria and Device Performance

• At +25%, +50%, +75%, +100% of cutoff (31.25, 37.5, 43.75, 50 ng/mL): 100% Positive results (80/80 replicates).
• At Cutoff (25 ng/mL): Expected to show a mix of positive and negative results, demonstrating it acts as a boundary. | Qualitative Analysis (25 ng/mL cutoff):
• 0 ng/mL: 80 Negative
• 6.25 ng/mL: 80 Negative
• 12.5 ng/mL: 80 Negative
• 18.75 ng/mL: 80 Negative
• 25 ng/mL (Cutoff): 60 Positive / 20 Negative
• 31.25 ng/mL: 80 Positive
• 37.5 ng/mL: 80 Positive
• 43.75 ng/mL: 80 Positive
• 50 ng/mL: 80 Positive

Interpretation: The device meets the criteria by exhibiting clear negative results below the cutoff, clear positive results above the cutoff, and a mixed result at the cutoff, confirming its function as a boundary. |
| Precision/Cutoff Characterization (Semi-Quantitative) | - Demonstrates consistent mean values and acceptable repeatability (SD, CV%) across concentrations.

• Accurately distinguishes negative and positive samples around the cutoff. | Semi-quantitative Analysis (25 ng/mL cutoff):
• 0 ng/mL: Mean 0 ng/mL, 80 Negative
• 6.25 ng/mL: Mean 7 ng/mL, CV 3.8% (Repeatability), CV 7.7% (Within-Lab), 80 Negative
• 12.5 ng/mL: Mean 12 ng/mL, CV 2.2% (Repeatability), CV 4.0% (Within-Lab), 80 Negative
• 18.75 ng/mL: Mean 18 ng/mL, CV 1.8% (Repeatability), CV 3.3% (Within-Lab), 80 Negative
• 25 ng/mL (Cutoff): Mean 25 ng/mL, CV 1.6% (Repeatability), CV 3.4% (Within-Lab), 60 Positive / 20 Negative
• 31.25 ng/mL: Mean 30 ng/mL, CV 2.2% (Repeatability), CV 2.7% (Within-Lab), 80 Positive
• 37.5 ng/mL: Mean 37 ng/mL, CV 1.4% (Repeatability), CV 3.3% (Within-Lab), 80 Positive
• 43.75 ng/mL: Mean 43 ng/mL, CV 1.5% (Repeatability), CV 4.6% (Within-Lab), 80 Positive
• 50 ng/mL: Mean 51 ng/mL, CV 1.3% (Repeatability), CV 4.5% (Within-Lab), 80 Positive

Interpretation: The device shows good semi-quantitative precision with low CVs and correct qualitative interpretation based on its quantitative output. |
| Recovery Study | - Expected % Recovery close to 100% for various spiked Pcp concentrations. | Recovery Study:

• Samples spiked from 4.0 to 80.0 ng/mL. % Recovery ranged from 98.5% to 112.0%.

Interpretation: The device demonstrates good analytical recovery of Pcp across a range of concentrations. |
| Method Comparison (Qualitative) | - High agreement (sensitivity and specificity) when compared to the reference method (GC/MS). | Summary of Qualitative Results (compared to GC/MS):

• Atellica Positive / GC/MS Positive: 53
• Atellica Negative / GC/MS Positive: 3 (False Negatives)
• Atellica Positive / GC/MS Negative: 1 (False Positive)
• Atellica Negative / GC/MS Negative: 55

Qualitative Assay Performance for 25 ng/mL cutoff (compared to GC/MS):

• Atellica Pos: 98% Agreement (for samples 38 ng/mL)
• Atellica Neg: 95% Agreement (for samples 38 ng/mL)

Interpretation: The device shows high agreement with the GC/MS reference method, indicating good performance in distinguishing positive and negative samples. |
| Method Comparison (Semi-Quantitative) | - High agreement (sensitivity and specificity) when compared to the reference method (GC/MS). | Summary of Semi-Quantitative Results (compared to GC/MS):

• Atellica Positive / GC/MS Positive: 53
• Atellica Negative / GC/MS Positive: 3 (False Negatives)
• Atellica Positive / GC/MS Negative: 1 (False Positive)
• Atellica Negative / GC/MS Negative: 55

Semi-Quantitative Assay Performance for 25 ng/mL cutoff (compared to GC/MS):

• Atellica Pos: 98% Agreement
• Atellica Neg: 95% Agreement

Interpretation: Similar high agreement as the qualitative assessment for the semi-quantitative mode. |
| Interference (pH, Specific Gravity, Endogenous Compounds, Unrelated Compounds) | - No false positive or false negative results within specified ranges/concentrations for various interfering substances. | Effect of pH: No interference observed across pH 3.1-11.0 for samples at -25% and +25% of cutoff.
Effect of Specific Gravity: No interference observed across SG 1.000-1.030 for samples at -25% and +25% of cutoff.
Effect of Endogenous Compounds: No false response for compounds like Acetone, Ascorbic Acid, Bilirubin, Creatinine, Ethanol, etc., at stated concentrations for samples at -25% and +25% of cutoff.
Effect of Structurally Unrelated Compounds: No false response for numerous drugs (e.g., Acetaminophen, Amitriptyline, Caffeine, Ibuprofen, etc.) at high concentrations for samples at -25% and +25% of cutoff.
Boric Acid: Noted as causing a "false negative result," with the package insert notifying users of this limitation.

Interpretation: The device generally demonstrates good resistance to common interferences, except for Boric Acid, which is acknowledged as a limitation. |
| Cross-Reactivity (Structurally Similar Compounds) | - Quantified cross-reactivity for structurally similar compounds. The specific acceptance criteria for these percentages are not explicitly stated as pass/fail, but rather as performance characteristics to be reported. | Summary of Cross-reactivity: Various compounds showed cross-reactivity ranging from 0.01% (e.g., Diphenhydramine, Doxepin) to 74.38% (trans-4-phenyl-4-Piperidinocyclohexanol), with 4-Methoxyphencyclidine at 8.43%, 1-(1-Phenylcyclohexyl)pyrrolidine (PCPy) at 38.33% and 1-[1-(2-Thienyl)-cyclohexyl]piperidine (TCP) at 58.11%.

Interpretation: The device shows varying degrees of cross-reactivity with structurally similar compounds, which is expected for immunoassay methods. The specific values are provided for user information. |

Study Details:

1. Sample size used for the test set and the data provenance:

   • Precision/Cutoff Characterization: 80 replicates were used for each of the 9 concentration levels tested (a total of 720 measurements). The provenance is not explicitly stated but is implied to be laboratory-prepared urine pools.
   • Recovery Study: 10 samples with varying spiked Pcp concentrations were tested. Provenance is laboratory-prepared drug-free urine spiked with Pcp.
   • Method Comparison: Clinical urine samples were used. The document mentions "Anonymous, discarded clinical urine samples" and refers to "native urine samples." The exact number of clinical samples is not specified numerically, but the contingency tables show totals of 112 for both qualitative and semi-quantitative analysis against GC/MS (53+1+3+55).
   • Interference Studies:
     • pH, Specific Gravity, Endogenous, Unrelated Compounds: Samples spiked at -25% and +25% of the cutoff were used. The number of samples for each interferent is not specified, but typically this involves replicates. The provenance is laboratory-prepared drug-free urine containing target analytes and spiked interferents.
     • Cross-reactivity: Structurally similar compounds were spiked into drug-free urine at indicated levels. The number of samples is not specified. Provenance is laboratory-prepared urine.
   • Data Provenance: The device performance studies appear to be laboratory-based ("clinical urine samples," "drug-free urine pool," "spiked... stock"). There is no mention of country of origin, but given the FDA submission, it's likely US-based or following international standards accepted by the FDA. The nature of the samples ("discarded clinical urine samples," "spiked") indicates a retrospective approach to sample collection for the method comparison, while the other studies are prospective in design (laboratory testing).

2. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

   • For the Method Comparison study, the ground truth was established by Gas Chromatography/Mass Spectrometry (GC/MS), which is stated as the "preferred confirmatory method." GC/MS is an objective analytical method; therefore, human experts are not directly involved in establishing the truth for individual samples in the same way they would for image interpretation. The expertise lies in operating and interpreting GC/MS data, but the "ground truth" itself is the chemical analysis result.
   • For other studies (Precision, Recovery, Interference), the ground truth is based on the known concentrations of Pcp in the spiked or prepared samples.

3. Adjudication method for the test set:

   • No adjudication method (e.g., 2+1, 3+1) is mentioned as the ground truth for the method comparison was established by GC/MS, a definitive chemical analysis.

4. If a multi reader multi case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance:

   • This is an in vitro diagnostic (IVD) device for chemical analysis (enzyme immunoassay for Phencyclidine in urine). Therefore, no MRMC comparative effectiveness study was done as it's not applicable for this type of device. There are no human "readers" or "AI assistance" in the context of interpreting results. The device performs the test and provides a result.

5. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:

   • Yes, this is effectively a standalone device performance study. The Atellica CH Phencyclidine (Pcp) assay operates as an automated system (Atellica CH Analyzer) without human intervention in the analytical process itself. The performance data presented (precision, recovery, method comparison, interference, cross-reactivity) are all based on the algorithm/instrument's output alone. While human technicians operate the analyzer, the decision-making for a result (positive/negative) is driven by the instrument's measurement against the defined cutoff of 25 ng/mL.

6. The type of ground truth used (expert consensus, pathology, outcomes data, etc):

   • The primary ground truth for the Method Comparison study was Gas Chromatography/Mass Spectrometry (GC/MS) results, which is a definitive analytical method for phencyclidine.
   • For Precision, Recovery, Interference, and Cross-reactivity studies, the ground truth was based on known, prepared concentrations of phencyclidine or interfering substances in urine samples.

7. The sample size for the training set:

   • The document describes performance testing data for the Atellica CH Phencyclidine (Pcp) assay. It does not mention a "training set" in the context of an AI/machine learning model. This is an immunoassay, which is a chemical reaction-based test, not a software algorithm that undergoes training. Therefore, N/A for a training set in the AI sense.

8. How the ground truth for the training set was established:

   • As this is not an AI/machine learning device, the concept of a "training set" and its associated ground truth establishment is not applicable. The device's performance is based on its fixed chemical assay design.

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