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The Cylex Immune Cell Function Assay measures the concentration of ATP from circulating CD4 cells following in vitro stimulation with phytohemagglutinin (PHA) as an indicator of immune cell function. This measurement is made on heparin anticoagulated whole blood using a luminometer and luciferin/luciferase. The assay is used for the detection of cell mediated immune response in populations undergoing immunosuppressive therapy for organ transplant.

The Cylex Immune Cell Function Assay detects cell-mediated immunity (CMI) by measuring the concentration of ATP from CD4 cells following stimulation. This measurement is made on heparin anti-coagulated whole blood using a luminometer and luciferin/luciferase. The assay is used for the detection of cell-mediated immunity in an immunosuppressed population.

Device Description

The Cylex Immune Cell Function Assay measures the concentration of ATP following in vitro stimulation with phytohemagglutinin (PHA) as an indicator of immune cell function. This measurement is made on heparin anti-coagulated whole blood using a luminometer and luciferin/luciferase. The assay is used for the detection of cell mediated immune response in populations undergoing immunosuppressive therapy for organ transplant.

The Cylex Immune Cell Function Assay detects cell-mediated immunity in whole blood. Following incubation, increased ATP synthesis occurs within the cells that respond to the stimulant phytohemagglutinin (PHA). Concurrently, whole blood to monoclonal antibody coated magnetic particles are added to immunoselect CD4 cells from both the stimulated and non-stimulated wells. After washing the selected CD4 cells on a magnet tray, Lysis Reagent is added to release intracellular ATP. Through the released ATP produces light according to the following equation: Luciferin + ATP + O2 Luciferase Mo Oxyluciferin + AMP + Pyrophosphate + CO2 + Light. The amount of light measured by a luminometer (emission maximum 562 nm) is proportional to the concentration of ATP. The concentration of ATP (ng/mL) is calculated from a calibration curve to characterize the cellular immune function of the sample.

AI/ML Overview

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

Cylex Inc. Immune Cell Function Assay

1. Table of Acceptance Criteria and Reported Device Performance

The provided text does not explicitly state pre-defined "acceptance criteria" in terms of specific thresholds for sensitivity, specificity, or similar performance metrics that the device had to meet to be approved. Instead, it presents the results of a clinical study aimed at demonstrating the device's ability to differentiate between two distinct populations (healthy vs. immunosuppressed transplant recipients) and comparing its statistical performance to a predicate device.

The primary demonstration of performance is the statistical difference in ATP measurements between the two patient populations.

Performance Metric	Cylex ICF Assay	Comparator Assay (CD4 Count)
Statistical Difference between Healthy and Transplant Populations	p < 0.0001 (Highly significant) - Means are statistically significantly different.	p < 0.0001 (Highly significant) - Means are statistically significantly different.
Healthy (Non-immunusuppressed) Population
n	40	40
Mean ATP (ng/mL)	464	N/A
Mean CD4 Count (cells/µL)	N/A	746
SD ATP (ng/mL)	145	N/A
SD CD4 Count (cells/µL)	N/A	431
Median ATP (ng/mL)	443	N/A
Median CD4 Count (cells/µL)	N/A	654
Range of Values ATP (ng/mL)	243-967	N/A
Range of Values CD4 Count (cells/µL)	N/A	130-2659
Transplant (Immunosuppressed) Population
n	63	63
Mean ATP (ng/mL)	304	N/A
Mean CD4 Count (cells/µL)	N/A	542
SD ATP (ng/mL)	163	N/A
SD CD4 Count (cells/µL)	N/A	423
Median ATP (ng/mL)	293	N/A
Median CD4 Count (cells/µL)	N/A	503
Range of Values ATP (ng/mL)	58-759	N/A
Range of Values CD4 Count (cells/µL)	N/A	<68*-1904
Distribution of Results (Cylex ICF Assay)
Patients ≤225 ATP ng/mL (Transplant)	38% (24/63)	N/A
Patients ≤225 ATP ng/mL (Healthy)	0% (0/40)	N/A
Patients 226-524 ATP ng/mL (Transplant)	52% (33/63)	N/A
Patients 226-524 ATP ng/mL (Healthy)	67% (27/40)	N/A
Patients ≥525 ATP ng/mL (Transplant)	10% (6/63)	N/A
Patients ≥525 ATP ng/mL (Healthy)	33% (13/40)	N/A
Distribution of Results (Total CD4 Count)
Patients <410 cells/µL (Transplant)	N/A	46% (29/63)
Patients <410 cells/µL (Healthy)	N/A	20% (8/40)
Patients ≥410 cells/µL (Transplant)	N/A	54% (34/63)
Patients ≥410 cells/µL (Healthy)	N/A	80% (32/40)

Note: The primary "acceptance criteria" appear to be establishing statistical significance in differentiating between healthy individuals and immunosuppressed transplant recipients, which was met (p < 0.0001 for the Cylex assay and the comparator assay).

2. Sample Size Used for the Test Set and Data Provenance

Test Set Sample Size:
- Apparently Healthy Adults: 44 (40 included in calculations after outlier exclusion)
- Transplant Recipients: 78 (63 included in calculations after outlier exclusion)
- Total: 122 (103 included in calculations after outlier exclusion)
Data Provenance: The study was a "multi-center study" but the specific country of origin is not explicitly stated. The context (FDA 510(k) submission) suggests it was conducted in the US or under US regulatory guidelines. The study used "freshly drawn blood," indicating a prospective data collection.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications

The document does not mention the use of experts to establish ground truth for the test set. The "ground truth" for classifying patients was based on their clinical status: "apparently healthy adults" vs. "transplant recipients (undergoing immunosuppressive therapy)". The comparator assay (Becton Dickinson TriTest™/MultiTest™ CD4 counts) also served as a comparison point, but not as an expert-adjudicated ground truth.

4. Adjudication Method for the Test Set

No explicit adjudication method (e.g., 2+1, 3+1) is mentioned. The classification was based on the patient's clinical status (healthy vs. transplant recipient). Samples with %CV > 20% were excluded as outliers, which could be considered a form of data quality control.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done

No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not done. This study is for an in vitro diagnostic (IVD) assay measuring a biomarker, not for an imaging device or AI algorithm requiring human interpretation. Therefore, there's no mention of human readers or improved performance with AI assistance.

6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done

Yes, the study presents the standalone performance of the Cylex Immune Cell Function Assay. The reported ATP ng/mL values are solely generated by the device based on its intended mechanism (measuring ATP after PHA stimulation). There is no human interaction or interpretation involved in generating the primary raw data or the final ATP concentration.

7. The Type of Ground Truth Used

The ground truth used was clinical diagnosis/patient status:

"Apparently Healthy Adults" (non-immunosuppressed)
"Transplant Recipients" (immunosuppressed, undergoing therapy, with specific organ transplants listed).

8. The Sample Size for the Training Set

The document does not provide information about a separate "training set" or its sample size. This type of submission (510(k) for an IVD) focuses on the clinical performance study (test set) for device validation rather than an AI/machine learning model development process that typically involves distinct training, validation, and test sets.

9. How the Ground Truth for the Training Set Was Established

Since no training set is mentioned for this IVD submission, information on how its ground truth was established is not provided.

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