Search Results

The EnLite™ Neonatal TREC Kit is an in vitro diagnostic device intended for the semiquantitative determination of TREC (T-cell receptor excision circle) DNA in blood specimens dried on filter paper. The test is for use on the VICTOR™ EnLite instrument. The test is indicated for use as an aid in screening newborns for severe combined immunodeficiency disorder (SCID).

This test is not intended for use as a diagnostic test or for screening of SCID-like Syndromes, such as DiGeorge Syndrome, or Omenn Syndrome. It is also not intended to screen for less acute SCID syndromes such as leaky-SCID or variant SCID.

The EnLite™ Neonatal TREC Kit is comprised of the EnLite™ Neonatal TREC Kit, the VICTOR™ EnLite instrument and the EnLite™ workstation software. The EnLite™ Neonatal TREC Kit contains reagents sufficient for 384 reactions or 1152 reactions, and multi-level, dried blood spot (DBS) calibrators and controls. The DBS calibrators and DBS controls have been prepared from porcine whole blood with a hematocrit value of 48-55%, and contain purified salmon-sperm, TREC, and beta-actin DNA.

The EnLite™ Neonatal TREC Kit is an in vitro diagnostic device for semi-quantitative determination of T-cell receptor excision circles (TRECs) in dried blood specimens, used as an aid in screening newborns for severe combined immunodeficiency disorder (SCID).

1. Acceptance Criteria and Reported Device Performance

The acceptance criteria for the EnLite™ Neonatal TREC Kit are outlined in the regulatory information, specifically within the "Special Controls" section (Section T, point 1(iii)). These criteria detail the required analytical and clinical performance characteristics for the device. The reported device performance is presented throughout the "Performance Characteristics" section (Section M).

Here's a table summarizing key acceptance criteria and reported performance, focusing on the clinical validation study as that directly addresses the intended use of screening:

Table of Acceptance Criteria and Reported Device Performance

A minimum of 10-15 confirmed positive specimens from more than one site, with relevant annotation, and SCID diagnosis by flow cytometry or clinically meaningful information regarding subject status at one year or beyond.

Additional specimens characterized by other disorders with low/absent TREC (e.g., other T-cell lymphopenic disorders) to supplement the range of results.

Pre-specified clinical decision point (cut-off) before studies.

Results summarized in tabular format comparing interpretation to reference method.

Point estimates and 95% CIs for PPA, NPA, and OPA.

Data must include retest rate, false positive rate before retest, final false positive rate, and false negative rate. | The primary clinical study objective was to demonstrate the EnLite™ Neonatal TREC Kit's screening performance in the intended use population and its ability to discriminate between normal and SCID cases. The study was conducted retrospectively.

SCID Positive Specimens: 17 archived confirmed SCID positive DBS specimens were obtained from newborn screening laboratories in the US. All 17 were confirmed for SCID by flow cytometry. These enriched the study due to the low incidence of SCID.

Other Low TREC Specimens: An additional 9 DBS specimens from babies with low TREC values (0 to 20 TREC Copies/uL) were included.

Comparator: For routine clinical study specimens, the comparator was the clinical assessment from medical records at one year of age or older (365 days), confirming the newborn was not identified with SCID, was not deceased from SCID-related complications, and was apparently healthy. For confirmed SCID cases, the comparator was the reference tests results for SCID confirmation.

Pre-specified Cut-off: The cut-off for TREC was pre-determined to be 36 copies/uL and for beta-actin as 56 copies/uL, based on the 2.5th percentile of normal distribution data from a separate cut-off confirmation study using 2846 archived, retrospective newborn specimens from the Danish Newborn Screening Biobank.

Retest Rate: The retest rate was 1.9%.

False Positive Rate: The false positive rate using the cut-off of 36 in the first round of testing was 1.5%. After repeat testing on follow-up cases, the final false positive rate was 0.5%.

False Negative Rate: The clinical data indicates 0 false negative results among the 16 confirmed SCID positives classified after the final testing round (Table 14).

Performance (from Table 14, excluding invalid results):
- Overall Percent Agreement (OPA): 99.7% (95% CI: 99.4% to 99.8%)
- Positive Percent Agreement (PPA): 100% (95% CI: 79.4% to 100%)
- Negative Percent Agreement (NPA): 99.7% (95% CI: 99.4% to 99.8%)

Note: One SCID positive specimen in the clinical study was classified as an invalid result, leading to 16 confirmed SCID positives being used for final agreement calculations. |

2. Sample Sizes and Data Provenance

• Test Set Sample Size:

  • Clinical Study: A total of 6,471 neonatal specimens were run, with 6,373 included in the final analysis. This included 6,389 routine Danish newborn screening biobanked newborn routine DBS samples and 82 enrichment samples (17 confirmed SCID positive samples, 9 confirmed low-level TREC specimens, and 56 samples used for blinding purposes). For the final agreement calculations, 5,454 specimens (after some exclusions and loss-to-follow-up) were used, specifically 5,442 after removing invalid results (16 confirmed SCID positives and 5,426 normal/presumptive normal).
  • Cut-off Establishment Study: 3,243 archived, retrospective newborn specimens initially, with 2,846 included in the analysis after exclusions.
  • Analytical Performance Studies (Examples):
    • Reproducibility (Site-to-Site): 90 measurements per sample (6 unique TREC levels, 10 runs x 3 laboratories x 3 replicates/sample).
    • Precision: 27 runs performed over 20 days. For TREC precision, 10 samples were assessed with 4 replicates/sample. For beta-actin, 7 samples were used.
    • LoB/LoD/LoQ: 5 samples for LoB (60 results per sample); 5 samples for LoD/LoQ (108 results per sample).

• Data Provenance:

  • Clinical Study & Cut-off Establishment:
    • Country of Origin: Denmark (samples from the Danish Newborn Screening Biobank, comprising the Danish population).
    • Retrospective/Prospective: All samples were archived, retrospective.
  • SCID Enrichment Samples: 17 confirmed SCID positive DBS specimens were obtained from newborn screening laboratories in the US (retrospective).

3. Number of Experts and Qualifications for Ground Truth

The document does not explicitly state the number of experts used to establish the ground truth for the test set, nor their specific qualifications (e.g., "radiologist with 10 years of experience").

• However, the ground truth for the 17 confirmed SCID positive specimens was established by flow cytometry, which is a specialized laboratory test requiring expert interpretation, presumably by qualified clinical immunologists or pathologists.
• For the routine newborn specimens, the comparator for ground truth was the clinical assessment of the study subjects obtained from their medical records at one year of age or older (365 days), confirming they were not identified with SCID, were not deceased from SCID-related complications, and were apparently healthy. This clinical assessment would implicitly involve input from various medical professionals (pediatricians, specialists).
• The "expert" component primarily comes from the reference method (flow cytometry) for SCID diagnosis and the subsequent clinical follow-up for the larger cohort.

4. Adjudication Method for the Test Set

The adjudication method for the test set was not explicitly described as a multi-expert consensus process like "2+1" or "3+1" that is common in medical imaging studies. Instead, the ground truth for SCID confirmation was primarily based on:

• Laboratory Confirmation: Flow cytometry for the 17 confirmed SCID cases.
• Clinical Outcomes: Medical record review at one year of age or older for the large cohort of routine newborns to determine the absence of SCID.

The device itself has an internal retesting algorithm (Section P.4 and P.4, Figure 8). Initial results below the cut-off are "presumptive positive" and are retested in duplicate. This internal retesting acts as a form of "internal adjudication" for the device's own classification, but it's not external expert adjudication of the ground truth.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

No MRMC comparative effectiveness study was mentioned. This device is a laboratory diagnostic kit and not an AI-assisted diagnostic tool for human readers (like a CAD system for radiologists). Therefore, a study to measure how much human readers improve with AI vs. without AI assistance is not applicable to this type of device.

6. Standalone Performance

The study primarily assessed the standalone performance of the device/kit (EnLite™ Neonatal TREC Kit, VICTOR™ EnLite instrument, and EnLite™ workstation software) in classifying samples as "presumptive positive" or "normal" based on its quantitative TREC and beta-actin measurements and the predefined cut-offs. The results (PPA, NPA, OPA) reflect the performance of the integrated system in a laboratory setting, without direct human cognitive interpretation of raw data for diagnosis. The output from the device is a quantitative TREC value, which is then used with a hard cut-off.

7. Type of Ground Truth Used

The ground truth used was a combination of:

• Laboratory Test Confirmation: For the known SCID positive cases, flow cytometry was used to confirm SCID.
• Clinical Outcomes Data: For the large cohort of routine newborn screening samples, the absence of SCID was determined through medical record review (vaccination records, national patient registry, civil registration system) at one year of age or older, looking for signs of SCID or SCID-related complications/death.

8. Sample Size for the Training Set

The document describes the evaluation of an already developed device/kit, not a machine learning model. Therefore, there is no explicit "training set" in the context of machine learning model development. The data used for establishing the clinical cut-off (2,846 samples from the Danish Newborn Screening Biobank) could be considered analogous to a "development" or "calibration" dataset, which informed the final cut-off value used in the pivotal study (test set).

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

As noted above, there isn't a "training set" for a machine learning model. For the dataset used to establish the clinical cut-off (2,846 samples):

• These were archived, retrospective newborn specimens from the Danish Newborn Screening Biobank.
• The ground truth in this context was based on the distribution of TREC and beta-actin values in this "normal newborn population". The 2.5 percentile of this distribution was then chosen as the clinical cut-off for TREC (36 copies/uL) and beta-actin (56 copies/uL). This is a statistical approach to defining "normal" for screening purposes, rather than a direct disease diagnosis for each individual sample.

Ask a specific question about this device