(157 days)
The determination of hemoglobin Bart's in human whole blood using ion-exchange HPLC.
The VARIANT Alpha-Thalassemia Short Program is designed for use on the fully automated VARIANT analyzer. The analytical system consisting of instrument and reagent kit provides an assay for the detection of hemoglobin Bart's by High Performance Liquid Chromatography (HPLC). The VARIANT Alpha-Thalassemia Short Program utilizes the principles of cation exchange HPLC. A hemolysate is prepared by mixing whole blood with a hemolysis reagent included in the kit. The prepared hemolysate is placed into the instrument's auto sampler. The sampler injects a specified amount of hemolysate onto the cartridge. The separation of normal hemoglobin and Hb Bart's is accomplished on the cation exchange cartridge using a buffer gradient. A dual wavelength photometer (415 and 690 nm) monitors the elution of the separated hemoglobins from the cartridge, detecting absorbance changes at 415nm. The 690 nm secondary filter corrects the baseline for effects caused by the mixing of buffers of different ionic strengths as the gradient is formed. In the Variant «-Thalassemia Program, Retention Time Windows have been established for the quantitation of Hb Bart's and all non-Bart's hemoglobins, except Hb S and Hb C. These "windows" are expressed in time (minutes and fractions thereof) called retention time. Retention time relates to how long a peak takes from the point of injection to the apex of the peak representing a given hemoglobin. In the Variant «-Thalassemia Program, if a peak occurs within one of these preset windows, it is designated as the hemoglobin corresponding to that window. For example, if a peak falls in the "Bart's window" the report indicates that a peak was detected in the "Bart's window" and prints a quantitative value on the sample report. For quantitation, a calibrator, with an assigned Hb Bart's value which is entered into the software during setup of the assay, is placed at the beginning of a run. After the analysis of the calibrator, a calibration factor is determined from the ratio of the assigned value to the observed value. This calibration factor is applied to each subsequent sample in the run.
Here's an analysis of the provided text, outlining the acceptance criteria and the study that proves the device meets those criteria:
Acceptance Criteria and Device Performance Study for the VARIANT Alpha-Thalassemia Short Program
The objective of the study was to establish substantial equivalence of the VARIANT Alpha-Thalassemia Short Program to an existing device, the Isolab Alpha-Thal Screen test, thereby confirming its safety and effectiveness.
1. Table of Acceptance Criteria and Reported Device Performance
The document doesn't explicitly state "acceptance criteria" in a numerical or categorical format for demonstrating substantial equivalence. Instead, it relies on demonstrating comparable performance in key analytical metrics (precision, accuracy, and linearity) with the predicate device. The primary "acceptance criteria" for demonstrating substantial equivalence seems to be a high correlation coefficient with the predicate device.
| Performance Metric | Acceptance Criteria (Implied) | Reported Device Performance (VARIANT Alpha-Thalassemia Short Program) |
|---|---|---|
| Precision | Demonstrate acceptable within-run and day-to-day variability. | Within-Run Precision: |
- Low % Hb Bart's: SD 0.0, CV 0.0
- Medium % Hb Bart's: SD 0.1, CV 1.6
- High % Hb Bart's: SD 0.2, CV 1.1
Day-to-Day Precision: - Low % Hb Bart's: SD 0.1, CV 74.0
- Medium % Hb Bart's: SD 0.2, CV 3.2
- High % Hb Bart's: SD 0.7, CV 3.3 |
| Accuracy (Correlation with Predicate) | High correlation coefficient with the Isolab Alpha-Thal Screen test. | Correlation coefficient of 0.977 (vs. Isolab Alpha-Thal Screen) |
| Linearity | Demonstrate a linear response to increasing concentrations of Hb Bart's. | Correlation coefficient of 1.0 (for linearity study) |
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size for Test Set: 195 cord blood specimens were used for the accuracy (correlation) study comparing the VARIANT Alpha-Thalassemia Short Program to the Isolab Alpha-Thal Screen test.
- Data Provenance: The document does not explicitly state the country of origin. It is a retrospective study, as it involved analyzing existing cord blood specimens.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications
The ground truth for the test set was established by the Isolab Alpha-Thal Screen test, which is the predicate device. The document does not mention the use of additional human experts (e.g., radiologists) for establishing ground truth or interpretation in this context. The "ground truth" for the comparison was the results obtained from the established, existing device.
4. Adjudication Method for the Test Set
No adjudication method is mentioned. The comparison was directly between the results generated by the new device and the predicate device.
5. If a Multi Reader Multi Case (MRMC) Comparative Effectiveness Study Was Done
No, an MRMC comparative effectiveness study was not conducted. This study focuses on the analytical performance of the device itself by comparing it to an existing device, rather than evaluating the impact of the device on human reader performance.
6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done
Yes, the studies described are essentially standalone performance evaluations of the VARIANT Alpha-Thalassemia Short Program. The device, an automated HPLC system, quantifies Hb Bart's, and its performance (precision, accuracy, linearity) is assessed independently, with the Isolab Alpha-Thal Screen serving as the comparison standard for accuracy. There is no human interaction explicitly described as part of the "performance" during the testing phase beyond operating the instruments and analyzing the output.
7. The Type of Ground Truth Used
The primary ground truth used for the accuracy study was the results obtained from the predicate device, the Isolab Alpha-Thal Screen test.
For the linearity study, theoretical values calculated from mixing a hydrops sample with a normal sample served as the ground truth.
8. The Sample Size for the Training Set
The document does not mention a distinct "training set" or "training phase" in the context of machine learning or algorithm development. The VARIANT Alpha-Thalassemia Short Program is described as an analytical chemical system (HPLC) with established retention time windows and a calibration process. The "software" mentioned for calibrator entry doesn't imply a machine learning model that requires a separate training set.
9. How the Ground Truth for the Training Set Was Established
As no training set is discussed for a machine learning model, this question is not applicable. The device relies on pre-calibrated parameters and retention time windows, which would have been established during the device's development using characterized samples, but not referred to as a "training set" in the machine learning sense.
§ 864.7415 Abnormal hemoglobin assay.
(a)
Identification. An abnormal hemoglobin assay is a device consisting of the reagents, apparatus, instrumentation, and controls necessary to isolate and identify abnormal genetically determined hemoglobin types.(b)
Classification. Class II (special controls). A control intended for use with an abnormal hemoglobin assay is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 864.9.