(155 days)
The Magnesium assay is used for the quantitation of magnesium in human serum, plasma, or urine. Magnesium measurements are used in the diagnosis and treatment of hypomagnesemia (abnormally low serum levels of magnesium) and hypermagnesemia (abnormally high serum levels of magnesium).
Magnesium is an in vitro diagnostic assay for the quantitative determination of magnesium in human serum, plasma, or urine. The Magnesium assay is a clinical chemistry assay which utilizes an arsenazo dye which binds preferentially with magnesium. The absorbance of the arsenazo magnesium complex is measured at 550 nm and is proportional to the concentration of magnesium present in the sample. Calcium interference is prevented by incorporation of a calcium chelating agent.
Here's a summary of the acceptance criteria and the study details for the K981791 (Magnesium assay) device, based on the provided text:
Acceptance Criteria and Device Performance
The provided document describes a "substantial equivalence" study, where the new device (Abbott Laboratories Magnesium assay) is compared to a legally marketed predicate device (Boehringer Mannheim® Magnesium assay) to demonstrate similar performance characteristics. The acceptance criteria are implicitly defined by achieving "acceptable correlation" and displaying similar performance to the predicate device.
Table of Acceptance Criteria and Reported Device Performance
| Performance Characteristic | Acceptance Criteria (Implicit - demonstrating substantial equivalence to predicate) | Reported Device Performance (Abbott Magnesium Assay) |
|---|---|---|
| Serum Application: | ||
| Correlation Coefficient | Acceptable correlation to Boehringer Mannheim Magnesium assay | 0.9884 |
| Slope | Acceptable correlation to Boehringer Mannheim Magnesium assay | 0.961 |
| Y-intercept | Acceptable correlation to Boehringer Mannheim Magnesium assay | 0.134 mEq/L |
| Total %CV (Level 1) | Acceptable precision | 4.4% |
| Total %CV (Level 2) | Acceptable precision | 3.4% |
| Linearity | Comparable to predicate, or within clinically acceptable range | Up to 7.79 mEq/L |
| Limit of Quantitation | Comparable to predicate, or clinically acceptable sensitivity | 0.38 mEq/L |
| Urine Application: | ||
| Correlation Coefficient | Acceptable correlation to Boehringer Mannheim Magnesium assay | 0.9866 |
| Slope | Acceptable correlation to Boehringer Mannheim Magnesium assay | 1.068 |
| Y-intercept | Acceptable correlation to Boehringer Mannheim Magnesium assay | -0.222 mEq/L |
| Total %CV (Level 1) | Acceptable precision | 4.5% |
| Total %CV (Level 2) | Acceptable precision | 2.9% |
| Linearity | Comparable to predicate, or within clinically acceptable range | Up to 21.7 mEq/L |
| Limit of Quantitation | Comparable to predicate, or clinically acceptable sensitivity | (Not explicitly stated for urine, assumed to be same or similar to serum) |
Note on Acceptance Criteria: For a 510(k) submission, "substantial equivalence" is the primary acceptance criterion. This means the device performs as safely and effectively as a legally marketed predicate device. The specific numerical targets for correlation, slope, intercept, and CVs are not explicitly stated as "acceptance criteria" but are reported as the results that demonstrate this substantial equivalence. They are implicitly acceptable because the conclusion states the assay "yielded acceptable correlation" and the overall performance is "substantially equivalent."
Study Details
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Sample Size used for the test set and the data provenance:
- Sample Size for Test Set: Not explicitly stated for either the serum or urine method comparison. The document mentions "comparative performance studies" and "precision studies... using two levels of control material." The number of patient samples used for the method comparison is not provided.
- Data Provenance: Not explicitly stated (e.g., country of origin). The study involved "human serum, plasma, or urine." It is retrospective since it involved collecting samples and testing them against a predicate.
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Number of experts used to establish the ground truth for the test set and the qualifications of those experts:
- This is an in vitro diagnostic assay for a quantitative measurement of magnesium. The ground truth for such devices is typically established through a reference method or comparison to an established, validated method (the predicate device in this case), rather than expert clinical consensus or interpretation of complex images. Therefore, the concept of "experts" establishing ground truth in the traditional sense (e.g., radiologists) does not apply here. The "ground truth" is essentially defined by the predicate device's performance.
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Adjudication method for the test set:
- Not applicable as this is a quantitative chemical assay, not an interpretive diagnostic device requiring adjudication of ambiguous results by experts.
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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:
- Not applicable. This is a standalone in vitro diagnostic assay. It does not involve human readers interpreting results with or without AI assistance.
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If a standalone (i.e. algorithm only without human-in-the loop performance) was done:
- Yes, this is a standalone device. The performance characteristics (correlation, precision, linearity, sensitivity) are reported for the assay itself (algorithm/methodology) without human intervention in the result determination process. The results are quantitative values rather than human-interpreted outputs.
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The type of ground truth used:
- Predicate Device Comparison: The ground truth for establishing substantial equivalence was the performance of the Boehringer Mannheim® Magnesium assay (K811194) on the Hitachi® 717 Analyzer. This established, legally marketed device serves as the reference against which the new device's performance is compared for accuracy and similarity. The precision, linearity, and sensitivity are intrinsic performance characteristics of the assay itself, evaluated against defined analytical standards.
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The sample size for the training set:
- Not applicable. This is an in vitro diagnostic assay, not an AI or machine learning model that requires a distinct "training set." The methodology (utilizing an arsenazo dye) is based on established chemical principles.
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How the ground truth for the training set was established:
- Not applicable, as there is no "training set" in the context of this chemical assay.
§ 862.1495 Magnesium test system.
(a)
Identification. A magnesium test system is a device intended to measure magnesium levels in serum and plasma. Magnesium measurements are used in the diagnosis and treatment of hypomagnesemia (abnormally low plasma levels of magnesium) and hypermagnesemia (abnormally high plasma levels of magnesium).(b)
Classification. Class I.