(204 days)
The accuDEXA is a dual-energy x-ray device indicated for use in measuring an index of the bone density of the middle finger of the nondominant hand (BMD). This BMD value is a relative indicator of bone density elsewhere in the body. The measurement is compared to similar measurements from patients of the same gender and ethnicity to provide t-scores (number of standard deviations above or below the mean for a reference group of young healthy individuals) and z-scores (number of standard deviations above or below the mean for a cohort of the same age). A t-score or a z-score may be used by a physician as one factor, in conjunction with other clinical indicators, to diagnose osteoporosis and other bone disorders. When a normative database of the same ethnicity and gender is not available, the BMD value may still be used to compare to the patient's own baseline value, for example in following the patient's response to treatment for osteoporosis.
Below normal bone density can be associated with a variety of conditions or disorders of bone. For example, the Society of Nuclear Medicine and American College of Nuclear Physicians has identified specific medical indications for measurement of a patient's bone mass: for patients with premenopausal oophorectomy, spontaneous menopause, or estrogen deficiency conditions; for treatment-related osteopenia; when the diagnosis of osteopenia is suggested or established by other means, such as x-ray; during long-term immobilization; for endocrinopathies known to be associated with osteopenia; for post-gastrectomy and other malabsorption states leading to osteopenia: during long-term corticosteroid therapy; for chronic renal disease, particularly in childhood or adolescence; and to monitor treatment programs for osteoporosis.
The accuDEXA device is a Dual Energy X-Ray Absorptiometer (DEXA) device. The device is intended to calculate an index of bone mineral density in the middle finger of the non-dominant hand. By changing the high voltage on the X-ray tube, two energies are produced. Each of the two settings produces an image of the finger and each image is analyzed using various algorithms to produce a value of bone mineral density (BMD) and bone mineral content (BMC). These values are compared with a normative database, yielding a t-score and a z-score. The t-score is the number of standard deviations that the patient is above or below the mean of a reference sample of young healthy individuals. The zscore is the number of standard deviations that the patient is above or below the mean of a reference sample of individuals of the same age as the patient.
Here's an analysis of the provided text regarding the Schick accuDEXA Bone Densitometer, focusing on acceptance criteria and the supporting study:
Schick accuDEXA Bone Densitometer Acceptance Criteria and Study
The provided document, a 510(k) Summary for the Schick accuDEXA Bone Densitometer, describes the device's performance characteristics through a study to demonstrate substantial equivalence to predicate devices. While explicit "acceptance criteria" in a numerical or threshold format are not directly stated, the document implies them through its claims of precision, accuracy, and correlation with predicate devices and ground truth.
1. Table of Acceptance Criteria and Reported Device Performance
Given the nature of a 510(k) submission, the "acceptance criteria" are implied by the demonstration of performance that supports substantial equivalence to existing devices. The document highlights key performance characteristics rather than specific pass/fail values.
| Acceptance Criterion (Implied) | Reported Device Performance |
|---|---|
| Precision (Repeatability) | "The accuDEXA measurements are very repeatable, even with repositioning." |
| Accuracy | "The very high correlation of the accuDEXA measurements with the ashed bone weights shows that the accuDEXA measurements are very accurate." |
| Correlation with Predicate Devices | "The good correlation of the accuDEXA measurement with measurements with the two predicate devices demonstrates that the accuDEXA results for the middle finger are at least as good an indicator of BMD as the currently marketed predicate devices." |
| Ability to Generate Clinical Scores | "A reference data base has been developed in a clinical study which allows the calculation of t-scores and z-scores for each patient." |
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size for Test Set: The document states the study was conducted "on cadavers" for precision and accuracy testing. It does not specify the exact number of cadavers or bone samples used in this study.
- Data Provenance: Retrospective, as it involves cadaveric tissue. The country of origin of the data is not specified.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications
- The document does not mention the number or qualifications of experts used to establish ground truth. The ground truth (ashed bone weights) is an objective physical measurement, not an expert interpretation.
4. Adjudication Method for the Test Set
- None specified. For the "ashed bone weights" ground truth, adjudication by experts would not be applicable, as it's a direct physical measurement.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
- No. The document does not describe a multi-reader multi-case (MRMC) comparative effectiveness study involving human readers with and without AI assistance. The study focuses on the device's intrinsic performance (precision and accuracy) and its correlation with predicate devices.
6. Standalone Performance Study
- Yes. The primary study described evaluates the "precision and accuracy of the accuDEXA device" and its correlation with ashed bone weights. This is a standalone assessment of the algorithmic performance in determining bone density.
7. Type of Ground Truth Used
- For the accuracy evaluation, the ground truth used was "ashed bone weights." This is an objective, quantitative physical measurement of true bone mineral content.
8. Sample Size for the Training Set
- The document mentions "A reference data base has been developed in a clinical study which allows the calculation of t-scores and z-scores for each patient." However, it does not specify the sample size of this clinical study that formed the normative database.
9. How the Ground Truth for the Training Set Was Established
- The ground truth for the "reference data base" (which acts as a training set for norm-based scoring) was established through "a clinical study." It is assumed that this clinical study involved measuring BMD in a population to derive mean and standard deviation values for different age, gender, and potentially ethnic groups, thereby establishing the normative data for t-scores and z-scores. The specific methods for establishing the "ground truth" (i.e., true bone density measurements in this clinical cohort) are not detailed beyond "measurements."
§ 892.1170 Bone densitometer.
(a)
Identification. A bone densitometer is a device intended for medical purposes to measure bone density and mineral content by x-ray or gamma ray transmission measurements through the bone and adjacent tissues. This generic type of device may include signal analysis and display equipment, patient and equipment supports, component parts, and accessories.(b)
Classification. Class II.