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Immunoassay for the in vitro quantitative determination of free thyroxine in human serum and plasma.

The Elecsys® test principle is based on competition principle. Total duration of assay: 18 minutes (37° C).
• 1st incubation (9 minutes): Sample (15 µL) and a specific anti-T4 antibody labeled with a ruthenium complex (75 µL).
• 2nd incubation (9 minutes): After addition of biotinylated T4 (75 µL) and streptavidin-coated microparticles (35 µL), the still-free binding sites of the labeled antibody become occupied, with formation of an antibody-hapten complex. The entire complex is 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 (0.4 second read frame).
Results are determined via a calibration curve which is instrument-specifically generated by 2-point calibration and a master curve provided via the reagent bar code.

The provided text describes a 510(k) summary for the "Elecsys® FT4 Assay," a device for the in vitro quantitative determination of free thyroxine in human serum and plasma. The acceptance criteria and the study proving the device meets these criteria are detailed through comparisons to a predicate device, the Enzymun-Test® FT4 (K900883).

Here's the breakdown of the information requested:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria are implicitly defined by comparing the performance characteristics of the Elecsys® FT4 to its predicate device, Enzymun-Test® FT4. The goal is to demonstrate substantial equivalence, meaning the new device is as safe and effective as the predicate.

• Low: Within-Run %CV: 0.49, Total %CV: 5.1
• Mid: Within-Run %CV: 1.17, Total %CV: 2.9
• High: Within-Run %CV: 4.43, Total %CV: 2.0 | Modified NCCLS (ng/dL):
• Sample Control 1: Within-Run %CV: 1.58, Total %CV: 3.54
• Sample Control 2: Within-Run %CV: 1.43, Total %CV: 2.72
• Unknown Sample: Within-Run %CV: 2.85, Total %CV: 2.85 |
  | Sensitivity (Lower Detection Limit) | 0.1 ng/dL (1.29 pmol/L) | 0.023 ng/dL (0.3 pmol/L) |
  | Method Comparison (vs. Enzymun-Test® FT4) | Least Squares: y = 0.88x + 0.15, r = 0.984, SEE = 0.199, N = 77 | Least Squares: y = 0.954x + 0.18, r = 0.981, SEE = 1.11, N = 315
  Passing/Bablok: y = 1.02x + 0.36, r = 0.981, SEE = 1.11, N = 315 |
  | Interfering Substances (Bilirubin) | No interference at 64.5 mg/dL | No interference at 25 mg/dL |
  | Interfering Substances (Hemoglobin) | No interference at 1 g/dL | No interference at 1 g/dL |
  | Interfering Substances (Lipemia) | No interference at 1250 mg/dL | No interference at 1500 mg/dL |
  | Interfering Substances (Biotin) | No interference at 200 ng/mL | No interference at 30 ng/mL |
  | Specificity (% Cross-reactivity L-T4) | 100 | 100 |
  | Specificity (% Cross-reactivity D-T4) | 100 | 100 |
  | Specificity (% Cross-reactivity L-T3) | 3.5 | 1.53 |
  | Specificity (% Cross-reactivity D-T3) | 2.9 | 1.38 |
  | Specificity (% Cross-reactivity 3-iodo-L-tyrosine) |

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