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510(k) Data Aggregation
(179 days)
The Elecsys Toxo IgG immunoassay is for the in vitro quantitative determination of IgG antibodies to Toxoplasma gondi in human serum and Li-heparin, K3-EDTA, and sodium citrate plasma. This assay is intended for use as an aid in the assessment of immune status and as an aid in the diagnosis of primary infection. The electrochemiluminescence immunoassay "ECLIA" is intended for use on the Elecsys and cobas e immunoassay analyzers. NOTE: This assay has not been cleared by the FDA for blood/plasma donor screening. Elecsys PreciControl Toxo IgG is used for quality control of the Elecsys Toxo IgG immunoassay on the Elecsys and cobas e immunoassay analyzers.
(1) The Elecsys Toxo IgG Immunoassay is a two-step sandwich immunoassay with streptavidin microparticles and electrochemiluminescence detection. In the first incubation, 10 µL of sample, a biotinylated recombinant T. gondii- specific antigen, and a T. gondii-specific recombinant antigen labeled with a ruthenium complex a form a sandwich complex. Then, after addition of streptavidin-coated microparticles, the complex becomes bound to the solid phase via interaction of biotin and streptavidin. The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed with ProCell. Application of a voltage to the electrode then induces chemiluminescent emission which is measured by a photomultiplier. Results are determined via a calibration curve which is instrument-specifically generated by 2-point calibration and a master curve provided via the reagent barcode. A human serum-based calibrator is provided with the test kit, and the recommended control material is PreciControl Toxo IgG. (2) The Elecsys Precicontrol Toxo IgG contains two levels of human serum with Toxo IgG antibodies.
The document describes the Elecsys Toxo IgG Test System, an immunoassay for the quantitative determination of IgG antibodies to Toxoplasma gondii.
Here's an analysis of the acceptance criteria and the study proving the device meets them:
1. Table of Acceptance Criteria and Reported Device Performance
The acceptance criteria for each reported performance characteristic are not explicitly stated in a single "acceptance criteria" section. However, based on the reported data, we can infer the criteria used:
| Performance Characteristic | Acceptance Criteria (Inferred) | Reported Device Performance |
|---|---|---|
| Method Comparison (vs. Reference Method) | ||
| US Routine Clinical Specimens | ||
| Negative Agreement | High negative agreement | 93.4% (310/332) (90.1%-95.8% CI) |
| Positive Agreement | High positive agreement | 100% (183/183) (98.0%-100.0% CI) |
| European Site Prospective Study | ||
| Negative Agreement | High negative agreement | 91.1% (288/316) (87.5-94.0% CI) |
| Positive Agreement | High positive agreement | 99.3% (151/152) (96.4-100.0% CI) |
| European Site Frozen Samples | ||
| Negative Agreement | High negative agreement | 68.1% (32/47) (52.9-80.9% CI) |
| Positive Agreement | High positive agreement | 99.7% (378/379) (98.5-100.0% CI) |
| Precision | Consistent and low variability | |
| Intrassay (Low Control) | Low SD | SD = 0.02-0.05 IU/mL |
| Intrassay (High Control) | Low CV% | 2.02-4.78 CV % |
| Intrassay (Plasma < 1 IU/mL) | Low SD | 0.014-0.079 SD IU/mL |
| Intrassay (Plasma > 1 IU/mL) | Low CV% | CV 1.76-3.09% |
| Inter-assay (Low Control) | Low SD | SD 0.047 -0.077 IU/mL |
| Inter-assay (High Control) | Low CV% | CV 2.9-5.1 % |
| Inter-assay (Plasma < 5 IU/mL) | Low SD | SD 0.039-0.089 IU/mL |
| Inter-assay (Plasma > 5 IU/mL) | Low CV% | CV 2.7-5.3% |
| Limit of Blank (LoB) | Clearly defined upper limit | 0.130 IU/mL |
| Limit of Detection (LoD) | Clearly defined lower limit | 0.175 IU/mL |
| Analytical Specificity (Cross-reactivity) | No significant cross-reactivity with common interfering substances (e.g., RF, ANA, EBV). Minimal impact from other infections. | No cross-reactivity or interference due to RF, ANA, and EBV. 4 out of 186 non-Toxo samples showed positive by Elecsys Toxo IgG or reference method. |
| Interferences (Icterus, Hemolysis, Lipemia, Biotin) | Recovery of positive samples within ± 20% of initial value. | Unaffected by icterus (< 684 µmol/L), hemolysis (< 1.24 mmol/L), lipemia (< 2000 mg/dL), and biotin (< 246 nmol/L). |
2. Sample Size Used for the Test Set and Data Provenance
- Method Comparison Studies (Test Set):
- US Routine Clinical Specimens: 332 negative samples and 183 positive samples, totaling 515 samples. Data Provenance: "US Routine Clinical Specimens" - suggests a retrospective collection from a US laboratory.
- European Site Prospective Study: 316 negative samples and 152 positive samples, totaling 468 samples. Data Provenance: "European Site Prospective study results" - indicates a prospective collection from a European site.
- European Site Frozen Sample Results: 47 negative samples and 379 positive samples, totaling 426 samples. Data Provenance: "European Site Frozen sample results" - indicates retrospective frozen samples from a European site.
- Analytical Specificity (Cross-reactivity) Study: 193 specimens tested. Data Provenance: Not explicitly stated, but likely from clinical labs, some of which are positive for other conditions.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
The document does not specify the "number of experts" or their "qualifications" for establishing the ground truth. The ground truth for the method comparison studies is established by a "reference method" (the predicate device, VIDAS TOXO IgG II Test System, K993319, or other established laboratory methods for classifying positive/negative).
4. Adjudication Method for the Test Set
The document does not describe an adjudication method involving multiple readers or experts for the test set. The comparison is made against a "reference method," implying that the outcome of the reference method serves as the ground truth.
5. 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
No MRMC comparative effectiveness study was mentioned. This device is an in vitro diagnostic immunoassay, not an AI-powered diagnostic imaging or interpretation tool that would typically involve human readers and such a study design.
6. If a Standalone (i.e. algorithm only without human-in-the loop performance) was done
Yes, the studies presented (e.g., method comparison, precision, analytical specificity) are all standalone performance evaluations of the Elecsys Toxo IgG Immunoassay itself, without human interpretation as part of the primary diagnostic step. The device provides a quantitative result (IU/mL) which is then used by clinicians, but the performance data reflects the device's inherent analytical capabilities.
7. The Type of Ground Truth Used (expert consensus, pathology, outcomes data, etc.)
The ground truth used for the method comparison studies is established by a reference method. For a diagnostic immunoassay, this typically means a legally marketed and established laboratory assay considered to be the best available method for determining the presence or absence of Toxoplasma gondii IgG antibodies. The predicate device, VIDAS TOXO IgG II Test System, is explicitly mentioned as the comparison standard, implying it serves as a key component of the ground truth or "reference standard" for comparison.
8. The Sample Size for the Training Set
The document does not explicitly mention a "training set" in the context of device development. For an immunoassay, the "training" typically refers to the development and optimization of the assay reagents, protocols, and cut-offs. The clinical samples used for validation are considered "test sets" to evaluate the finalized device performance.
9. How the Ground Truth for the Training Set Was Established
As no specific "training set" is described in the context of a separate study with established ground truth, this information is not available in the provided text. The development process for an immunoassay generally involves extensive analytical validation and optimization using well-characterized samples, which implicitly involve defining known positive and negative samples (ground truth) during development.
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