Search Results

The Focus Diagnostics' STRATIFY JCV® DxSelect™ assay is intended for the qualitative detection of antibodies to JC virus in human serum or plasma. The assay is intended for use in conjunction with other clinical data, in multiple sclerosis patients receiving or considering natalizumab therapy, as an aid in risk stratification for progressive multifocal leukoencephalopathy development. The assay is for professional use only.

The assay is not intended for donor screening. The performance of this assay has not been established for use in other immunocompromised patient populations or patients with different disease conditions or undergoing other treatments or in neonates and pediatric patient populations.

Device Description

The Focus Diagnostics' STRATIFY JCV® DxSelect™ test is an ELISA assay. JC virus-like particles (VLP) are pre-coated onto 96-well microiter plates. Diluted serum or plasma specimens and controls are incubated in the wells to allow JCV-specific antibodies present in the specimens to react with the JC VLP antigen. Nonspecific reactants are removed by washing. Peroxidase-conjugated anti-human antibodies are added to react with JCV-specific antibodies. Excess conjugate is removed by washing. Enzyme substrate and chromogen are added, and the color is allowed to develop. After adding the Stop Reagent, the resultant color change is quantified by a spectrophotometric reading of optical density (OD). Specimen OD readings are compared with Cut-Off Calibrator OD readings to determine results. Each specimen result is reported as an index value. A specimen with an index value that is greater than a specified upper cut-off is reported as positive for detectable JCV-specific antibodies, whereas a specimen with an index value less than the specified lower cut-off is reported as negative for detectable JCV-specific antibodies. A specimen with an index value that is equal to or between the upper and lower cut-off values is reported as indeterminate. An indeterminate result requires further evaluation in the confirmation (inhibition) assay.

In the confirmation assay, soluble JC VLP antigen will compete with plate bound JC VLP antigen for the JCV-specific antibodies present in the serum or plasma specimens. After washing away the unbound antibodies, peroxidase-conjugated anti-human antibodies are added and bind to any captured JCVspecific antibodies. Excess conjugate is removed by washing. Enzyme substrate and chromagen are added, and the color is allowed to develop. After adding the Stop Reagent, the resultant color change is quantified by a spectrophotometric reading of OD. The percent inhibition is calculated to confirm presence of JCV-specific antibodies in the specimens with a percent inhibition value that is greater than the specified cut-off are reported as positive for detectable JCV-specific antibodies, whereas specimens with percent inhibition values less than or equal to the cut-off are reported as negative for detectable JCV-specific antibodies.

AI/ML Overview

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 for STRATIFY JCV® DxSelect™

1. Table of Acceptance Criteria and Reported Device Performance

The document does not explicitly present a "table of acceptance criteria" in the traditional sense, but rather demonstrates performance against the predicate device and established clinical guidelines. The key performance metrics evaluated are Positive Percent Agreement (PPA) and Negative Percent Agreement (NPA) with a validated laboratory methodology (the predicate device) and JCV antibody positivity rate in certain patient populations.

Metric	Acceptance Criteria (Implicit from Predicate & Clinical Relevance)	Reported Device Performance
Agreement with Predicate (Pre-PML Samples)	High positive agreement (especially for pre-PML samples, as JCV antibody positivity is a necessary step for PML development). The predicate device itself serves as the benchmark.	100% Positive Agreement (31/31) with the validated assay (95% CI: 89.0% to 100%) for pre-PML samples.
Agreement with Predicate (Patients Receiving Natalizumab)	High Positive Percent Agreement and Negative Percent Agreement with the validated laboratory methodology used in clinical studies.	Positive Percent Agreement (PPA): 97.0% (385/397) (95% CI: 94.8% to 98.3%)
Negative Percent Agreement (NPA): 90.6% (281/310) (95% CI: 86.9% to 93.4%)
Agreement with Predicate (Patients Considering Natalizumab)	High Positive Percent Agreement and Negative Percent Agreement with the validated laboratory methodology used in clinical studies.	Positive Percent Agreement (PPA): 98.5% (326/331) (95% CI: 96.5% to 99.4%)
Negative Percent Agreement (NPA): 91.8% (268/292) (95% CI: 88.1% to 94.4%)
PML Risk Stratification (Clinical Utility)	The assay should be statistically informative, meaning the percentage of positive results in patients with PML (pre-PML) is significantly higher than in the general MS population.	The 100% JCV antibody positivity in 31 natalizumab-treated PML patients (pre-PML) was significantly different from the 58.7% JCV antibody positivity in the MS population, representing an approximately 2-fold increased risk of PML for JCV antibody positive individuals compared to the overall natalizumab-treated population. The relative risk of PML for JCV positive patients treated with ≥18 months of natalizumab was 30.4 (95% CI: 5.3 to 437.4) compared to JCV negative patients.
Reproducibility (Qualitative Results)	Consistency in qualitative results (Negative, Indeterminate, Positive) across sites, days, runs/operators, and within the assay.	High qualitative agreement (e.g., Negative Control: 89/90 ND, Positive Control: 90/90 D, Indeterminate Control: 90/90 I). Individual sample types (Plasma Low Positive, Serum Indeterminate) also showed high agreement, with varying levels of qualitative outcomes depending on the sample type's proximity to the cut-off.
Reproducibility (Quantitative Results)	Low coefficient of variation (%CV) for quantitative results (OD and Index values) across sites, days, runs/operators, and within the assay.	Overall %CV for Index values generally below 17%, with many values significantly lower (e.g., Positive Control Index: 3.7% total %CV; Indeterminate Control Index: 8.3% total %CV). For %Inhibition, total %CV generally below 12%.
Reproducibility at Lower Cut Point (%CV)	Low %CV near the lower cut-point to demonstrate precision.	Plasma: 2.3% %CV for Detection Assay (Index) and 2.2% %CV for Confirmation Assay (%Inhibition) near the lower cut-point.
Serum: 2.6% %CV for Detection Assay (Index) and 2.0% %CV for Confirmation Assay (%Inhibition) near the lower cut-point.
Cross-Reactivity (Specific Antibodies)	No detected reactivity with common antibodies (e.g., E. coli, M. tuberculosis, P. jiroveci).	0/3 detected for all three antibodies tested (Antibody to Escherichia coli, Antibody to Mycobacterium tuberculosis, Antibody to Pneumocystis jiroveci).
Cross-Reactivity (Polyoma Viruses)	No significant change in OD signal when spiked with BKV VLP, indicating no cross-reactivity with BKV.	No samples exhibited >45% change in OD signal when spiked with BKV VLP (ranged from -15% to 27%), indicating no cross-reactivity with BKV.
Interference (Endogenous Substances)	Observed differences in signal should not cause changes in interpretation for most common interferents (%Change from Baseline

Ask a Question

Ask a specific question about this device

Page 1 of 1