(837 days)
Ortho-mune OKT4A (CD4) Monoclonal Antibody (Murine) FITC Conjugate is used to identify and enumerate the percentage of CD4+ human T lymphocytes in whole blood by flow cytometry.
Identification and enumeration of abnormal levels of CD4lymphocytes may be clinically significant in the prognosis of secondary immunodeficiency diseases (acquired immunodeficiency syndrome [AIDS]).
AIDS is characterized by a severe reduction in T helper CD3+CD4+) lymphocytes and a decrease in the CD4:CD8 ratio. The CD4:CD8 ratio has been used as a predictor of time to the development of AIDS. CD4 counts should also be determined using a CD3/CD4 combination reagent to eliminate monocyte contamination (CD3-CD4+dim). CD4+lymphocytes (expressed as an absolute number, a percentage of lymphocytes or as a ratio of CD4+ to CD8+ T lymphocytes) represents the best single predictor of the progression of AIDS. CD4+ lymphocyte numbers usually start to decline relatively soon after human immunodeficiency virus (HIV) infection.
Ortho-mune OKT4A Monoclonal Antibody (Murine) FITC Conjugate contains the purified monoclonal antibody OKT4A conjugated to the fluorochrome fluorescein isothiocyanate.
Acceptance Criteria and Device Performance for Ortho-mune™OKT™4A (CD4) FITC Conjugate
This document outlines the acceptance criteria and performance data for the Ortho-mune™OKT™4A (CD4) Monoclonal Antibody (Murine) FITC Conjugate, as submitted in K951459. The study aimed to demonstrate substantial equivalence to the predicate device, CD4 (Leu™-3a) FITC.
1. Table of Acceptance Criteria and Reported Device Performance
The acceptance criteria for substantial equivalence are inferred from the performance characteristics presented, specifically demonstrating comparable results to the predicate device and acceptable reproducibility and linearity. Given the nature of a 510(k) submission for substantial equivalence, the "acceptance criteria" are implicitly met by showing that the new device performs "as well as" or "equivalently to" the predicate device on key performance metrics.
| Performance Characteristic | Acceptance Criteria (Implicit) | Reported Device Performance (Ortho-mune OKT4A) |
|---|---|---|
| Equivalence to Predicate | Mean and range of percent CD4+ cells for normal and AIDS/ARC populations should be comparable to the predicate device. Regression analysis (Ortho-mune vs. Predicate) should show a strong correlation (R-value close to 1) and a slope near 1 with a small intercept. | Normal Donors (N=206): Mean % CD4+ = 47.0 (Range: 12.4 - 68.7). Predicate (LEU-3a) Mean % CD4+ = 45.1 (Range: 14.6 - 64.6). |
| AIDS/ARC Patients (N=88): Mean % CD4+ = 18.3 (Range: 1.0 - 55.1). Predicate (LEU-3A) Mean % CD4+ = 17.2 (Range: 0.6 - 51.6). | ||
| Linear Regression: Y = 0.969 + 1.019(X), R = 0.985 (combining normal and AIDS/ARC populations). This demonstrates strong correlation and a slope very close to 1, indicating equivalence. | ||
| Within-Laboratory Reproducibility | Coefficients of Variation (CV) should be acceptably low across low, normal, and high CD4 levels, and 95% Confidence Intervals (CI) should demonstrate precision. | Mean Percent Positive & CV across 3 sites (N=10 per site, 10 replicates each): |
- Low CD4: Mean % (Site 1: 9.60, Site 2: 9.36, Site 3: 8.86); CV (Site 1: 7.60, Site 2: 6.12, Site 3: 5.47)
- Normal CD4: Mean % (Site 1: 47.38, Site 2: 47.19, Site 3: 48.54); CV (Site 1: 2.33, Site 2: 2.00, Site 3: 2.21)
- High CD4: Mean % (Site 1: 56.13, Site 2: 55.83, Site 3: 56.50); CV (Site 1: 1.93, Site 2: 1.79, Site 3: 2.09)
Demonstrated excellent within-laboratory reproducibility. |
| Between-Laboratory Reproducibility | Coefficients of Variation (CV) should be acceptably low across low, normal, and high CD4 levels, and 95% Confidence Intervals (CI) should demonstrate precision across different laboratories. | Mean Percent Positive & CV across 3 sites (N=10 samples, 10 replicates each): - Low CD4: Mean % = 9.25; CV = 4.09; +/- 95% CI = 1.63
- Normal CD4: Mean % = 47.70; CV = 1.53; +/- 95% CI = 3.14
- High CD4: Mean % = 56.15; CV = 0.60; +/- 95% CI = 1.46
Demonstrated excellent between-laboratory reproducibility. |
| Linearity | Linear regression analysis (observed vs. expected CD4+ counts) should show slopes indistinguishable from 1 and R-values close to 1,000 (R=1). | Slopes and R-values for 4 donors and overall: - Donor 1: Slope = 0.999 (CI 0.003), Intercept = 6.099 (CI 5.242), R = 1.000
- Donor 2: Slope = 1.000 (CI 0.001), Intercept = 0.395 (CI 2.226), R = 1.000
- Donor 3: Slope = 0.999 (CI 0.003), Intercept = 4.449 (CI 4.176), R = 1.000
- Donor 4: Slope = 1.000 (CI 0.001), Intercept = 0.285 (CI 1.316), R = 1.000
- All Donors: Slope = 0.999 (CI 0.001), Intercept = 2.777 (CI 1.655), R = 1.000
Demonstrates linear performance across 20 to 9000 cells/uL. |
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size for Equivalence Study:
- 206 normal donors
- 88 AIDS/ARC patients
- Total: 294 whole blood specimens.
- Sample Size for Reproducibility Studies:
- 10 normal donors for within-laboratory study (processed to create low, normal, high CD4 populations).
- 10 normal donors for between-laboratory study (processed to create low, normal, high CD4 populations).
- Sample Size for Linearity Study:
- Specimens from 4 normal donors (processed to produce low, normal, high numbers of lymphocyte subsets via concentration/dilution).
- Data Provenance: The studies were conducted at three external, geographically distinct sites. The data is prospective for the purpose of this submission, though the underlying specimens are from existing populations (normal donors and AIDS/ARC patients). The country of origin of the data is not explicitly stated but is implied to be the United States given the submission to the FDA.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications
No external experts were explicitly used to establish ground truth in the traditional sense of consensus reading. The "ground truth" for the comparative effectiveness study was the measurement obtained by the predicate device, CD4 (Leu-3a) FITC, using flow cytometry. For the reproducibility and linearity studies, the ground truth was derived from the measurements of the device itself (Ortho-mune OKT4A) against established laboratory methods (e.g., automated hematology analyzer for total lymphocyte count).
4. Adjudication Method for the Test Set
No adjudication method was used for the test set. The study directly compared the measurements obtained by the new device to those obtained by the predicate device for equivalence, and relied on statistical analysis of direct measurements for reproducibility and linearity.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done
No MRMC study was done, as this device is an immunophenotyping reagent for flow cytometry, not an imaging device requiring human reader interpretation in the same manner. The "human readers" (flow cytometry operators) would be operating the instruments rather than interpreting complex images. The focus was on the performance of the reagent itself. Therefore, comparing human reader improvement with and without AI assistance is not applicable here.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done
Yes, the studies evaluating the performance of the Ortho-mune OKT4A (CD4) FITC Conjugate can be considered "standalone" in the sense that they assess the direct analytical performance of the reagent itself, as measured by a flow cytometer. The flow cytometry process is automated in terms of cell counting and fluorescent signal detection, and the reagent's performance is objectively measured. While human operators are involved in sample preparation and instrument setup, the core performance metrics (staining, enumeration, reproducibility, linearity) characterize the reagent's analytical capability independently of direct "human interpretation" of results in the way an imaging AI might be evaluated.
7. The Type of Ground Truth Used
- For Equivalence Study: The predicate device, CD4 (Leu-3a) FITC, was used as the reference standard. The goal was to establish substantial equivalence, meaning the new device performs comparably to a legally marketed device. This is a form of comparative ground truth.
- For Reproducibility Studies: The measurements from the Ortho-mune OKT4A reagent itself, over multiple replicates and sites, were used to assess the consistency of its own performance. This relies on the inherent precision of the laboratory measurements.
- For Linearity Study: A combination of an automated hematology analyzer (for total lymphocyte count) and the CYTORONABSOLUTE flow cytometer (with the Ortho-mune reagent for percent positive CDx cells) was used. The "expected" values were calculated based on serial dilutions and established counts, which serves as a form of derived or calculated ground truth.
8. The Sample Size for the Training Set
The document does not explicitly mention a "training set" in the context of machine learning or AI development. This device is a monoclonal antibody reagent, and its development typically involves laboratory-based optimization (e.g., antibody titration, conjugation efficiency) rather than algorithm training with large datasets. The studies described here are for validation of the final product.
9. How the Ground Truth for the Training Set Was Established
As noted above, the concept of a "training set" and associated ground truth establishment for AI/machine learning is not applicable to this type of medical device (an immunophenotyping reagent). The development process would have involved standard biological and chemical methods to characterize the antibody and its conjugate, ensuring specificity and reactivity, but not a "training set" with ground truth in the AI context.
§ 864.5220 Automated differential cell counter.
(a)
Identification. An automated differential cell counter is a device used to identify one or more of the formed elements of the blood. The device may also have the capability to flag, count, or classify immature or abnormal hematopoietic cells of the blood, bone marrow, or other body fluids. These devices may combine an electronic particle counting method, optical method, or a flow cytometric method utilizing monoclonal CD (cluster designation) markers. The device includes accessory CD markers.(b)
Classification. Class II (special controls). The special control for this device is the FDA document entitled “Class II Special Controls Guidance Document: Premarket Notifications for Automated Differential Cell Counters for Immature or Abnormal Blood Cells; Final Guidance for Industry and FDA.”