A bioimpedance spectroscopy device for use on adult human patients, utilizing impedance ratios that are displayed as an L-Dex ratio that supports the measurement of extracellular fluid volume differences between the limbs and is presented to the clinician on an L-Dex scale as an aid to their clinical assessment of unilateral lymphedema of the arm and leg in women and the leg in men.

The device is only indicated for patients who will have or who have had lymph nodes, from the axillary and pelvic regions, either removed, damaged or irradiated.

SOZOhub PC software - a PC software package that is intended to be used only with the ImpediMed SOZO device for uploading data on to the PC from the SOZO device, processing and analyzing of bioimpedance measurements.

Device Description

The SOZO system consists of a connected hand and footplate with built-in stainless steel electrodes, paired with an Android tablet over Bluetooth connection. An app ("SOZOapp"), supplied with the tablet, controls the functionality of the hardware and supplies the bioimpedance measurement data to a database ("SOZOhub") contained within the hospital/facility network.

Measurements require the patient to make contact with bare hands and feet on stainless steel electrodes. The measurement takes about 30 seconds, during which the SOZO system measures small quantities of electrical energy (200ua RMS) across 256 frequencies, spaced logarithmically from 3kHz to 1000kHz. Established algorithms are used to analyze data and calculate extracellular fluid impedance levels for left and right limbs, and present the impedance ratio as an L-Dex® score for the clinician to review. This score facilitates their clinical assessment of unilateral lymphedema of the arm and leg in woman, and the leg in men.

AI/ML Overview

Here's an analysis of the provided text regarding the acceptance criteria and study proving the device meets those criteria, formatted to address your specific points.

First, it's important to note that the provided documentation is a 510(k) premarket notification letter and summary for the SOZO™ device, which is an Impedance Plethysmograph (specifically, a bioimpedance spectroscopy device for assessing lymphedema). This type of submission primarily focuses on demonstrating substantial equivalence to a legally marketed predicate device, rather than proving efficacy through clinical trials with defined acceptance criteria and effect sizes as might be required for a PMA (Premarket Approval). Therefore, some of your requested information (e.g., effect size of human readers improving with AI, specific acceptance criteria for a clinical outcome, detailed ground truth establishment for a large test set) may not be present or applicable in this context.

The document emphasizes design changes to an existing technology (the L-Dex® U400) and the SOZO system's equivalence to that predicate. The "performance data" section primarily covers engineering and non-clinical testing.

Acceptance Criteria and Device Performance Study Analysis

1. Table of Acceptance Criteria and Reported Device Performance

The document does not present a formal table of "acceptance criteria" for clinical performance in the sense of a clinical trial. Instead, the performance data focuses on demonstrating that the new design of the SOZO system functions reliably and maintains characteristics similar to its predicate device. The "acceptance criteria" are implied by the successful completion of various engineering and non-clinical tests.

Acceptance Criteria (Implied)	Reported Device Performance
Electrical Safety/EMC Compliance (e.g., IEC 60601 standards)	Met electrical safety and EMC requirements; CB certificate granted.
Software Verification & Validation (e.g., ISO 62304)	Software verified and validated to meet acceptance criteria and perform as intended.
Biocompatibility (e.g., ISO 10993 standards)	Passed biocompatibility testing with no failures reported.
Correlation with Predicate Device (L-Dex Readings)	Very strong correlation (r > 0.99) with the cleared U400 system.
Functional Performance/Design Reliability	Expected to remain functional throughout its intended life (tested with repeated weights).

2. Sample Size Used for the Test Set and Data Provenance

The provided text does not specify a sample size for a clinical "test set" involving human subjects for performance evaluation. The "comparative performance vs. predicate device" was conducted using a "test fixture to create multiple fixed impedance loads representing different 'humans'." This is a laboratory-based, non-clinical test.

Sample Size for Test Set: Not applicable for a human clinical test set. The comparative test used a "test fixture" with "multiple fixed impedance loads."
Data Provenance: The testing appears to be primarily laboratory-based, likely conducted by the manufacturer (ImpediMed Limited, Australia) or accredited third-party labs. It is not described as involving retrospective or prospective human clinical data.

3. Number of Experts Used to Establish Ground Truth for the Test Set and Qualifications

This information is not applicable as the "test set" was not a human clinical dataset requiring expert interpretation. The ground truth for the device's measurements is based on the physical properties of the "fixed impedance loads" used in the test fixture.

4. Adjudication Method for the Test Set

Not applicable, as there was no human-interpreted test set requiring adjudication.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, and Effect Size

No, an MRMC comparative effectiveness study was not done. The device (SOZO) provides an L-Dex ratio, which is then used by a clinician as an "aid to their clinical assessment." This submission demonstrates the fidelity of the SOZO device's measurements compared to its predicate, not the impact on human reader performance. Therefore, there's no mention of an effect size for human readers improving with AI vs. without AI assistance because this is not an AI-based diagnostic tool in the sense that it provides an assessment directly to the clinician that then gets compared to human performance. It is a measurement device.

6. If a Standalone (i.e., Algorithm Only Without Human-in-the-Loop Performance) Was Done

The device's core functionality is its standalone measurement capability. The "L-Dex ratio" is a direct output of the device's algorithms based on bioimpedance spectroscopy data. The comparative test against the predicate device using a test fixture effectively evaluates this "standalone" measurement performance in a controlled environment. The "very strong correlation (r > 0.99)" reported indicates its standalone performance similarity to the predicate.

7. The Type of Ground Truth Used

The "ground truth" for the comparative performance study was the known, "fixed impedance loads" created by the test fixture. This serves as a known standard against which the measurements of both the SOZO device and the predicate U400 system were compared.

8. The Sample Size for the Training Set

The document does not specify a sample size for a "training set." This is likely because the device is based on "established algorithms" (Section 3: Device Description) and bioimpedance spectroscopy principles, rather than a machine learning model that would typically require a distinct training dataset to learn patterns. The focus is on the hardware and software's ability to accurately apply these existing algorithms and measure bioimpedance correctly.

9. How the Ground Truth for the Training Set Was Established

As there's no mention of a traditional "training set" for a machine learning model, the concept of establishing ground truth for it is not applicable in this document. The device relies on established scientific principles and algorithms for bioimpedance analysis, which were presumably developed and validated over time, but not detailed as a "training set" here.

Summary

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Food and Drug Administration 10903 New Hampshire Avenue Document Control Center - WO66-G609 Silver Spring, MD 20993-0002

August 11, 2017

ImpediMed Limited % Reuben Lawson Senior Director, Regulatory Affairs and Clinical ImpediMed Inc. 5900 Pasteur Court, Unit 125 Carlsbad. CA 92008

Re: K172122 Trade/Device Name: SOZO™ Regulation Number: 21 CFR§ 870.2770 Regulation Name: Impedance Plethysmograph Regulatory Class: II Product Code: OBH Dated: July 13, 2017 Received: July 13, 2017

Dear Reuben Lawson:

We have reviewed your Section 510(k) premarket notification of intent to market the device referenced above and have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments, or to devices that have been reclassified in accordance with the provisions of the Federal Food. Drug. and Cosmetic Act (Act) that do not require approval of a premarket approval application (PMA). You may, therefore, market the device, subject to the general controls provisions of the Act. The general controls provisions of the Act include requirements for annual registration, listing of devices, good manufacturing practice, labeling, and prohibitions against misbranding and adulteration. Please note: CDRH does not evaluate information related to contract liability warranties. We remind you, however, that device labeling must be truthful and not misleading.

If your device is classified (see above) into either class II (Special Controls) or class III (PMA), it may be subject to additional controls. Existing major regulations affecting your device can be found in the Code of Federal Regulations, Title 21, Parts 800 to 898. In addition, FDA may publish further announcements concerning your device in the Federal Register.

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Please be advised that FDA's issuance of a substantial equivalence determination does not mean that FDA has made a determination that your device complies with other requirements of the Act or any Federal statutes and regulations administered by other Federal agencies. You must comply with all the Act's requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Part 801); medical device reporting (reporting of medical devicerelated adverse events) (21 CFR 803); good manufacturing practice requirements as set forth in the quality systems (QS) regulation (21 CFR Part 820); and if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR 1000-1050.

If you desire specific advice for your device on our labeling regulation (21 CFR Part 801), please contact the Division of Industry and Consumer Education at its toll-free number (800) 638-2041 or (301) 796-7100 or at its Internet address

http://www.fda.gov/MedicalDevices/ResourcesforYou/Industry/default.htm. Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR Part 807.97). For questions regarding the reporting of adverse events under the MDR regulation (21 CFR Part 803), please go to

http://www.fda.gov/MedicalDevices/Safety/ReportaProblem/default.htm for the CDRH's Office of Surveillance and Biometrics/Division of Postmarket Surveillance.

You may obtain other general information on your responsibilities under the Act from the Division of Industry and Consumer Education at its toll-free number (800) 638-2041 or (301) 796-7100 or at its Internet address

http://www.fda.gov/MedicalDevices/ResourcesforYou/Industry/default.htm.

Sincerely,

Joyce M. Whang -S

for

Benjamin R. Fisher, Ph.D. Director Division of Reproductive, Gastro-Renal, and Urological Devices Office of Device Evaluation Center for Devices and Radiological Health

Enclosure

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DEPARTMENT OF HEALTH AND HUMAN SERVICES Food and Druq Administration Indications for Use

Form Approved: OMB No. 0910-0120 Expiration Date: January 31, 2017 See PRA Statement on last page

510(k) Number (if known)	K172122
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sozo™ Device Name

Indications for Use (Describe)

The device is only indicated for patients who will have or who have had lymph nodes, from the axillary and pelvic regions, either removed, damaged or irradiated.

Type of Use (Select one or both, as applicable)
☒ Prescription Use (Part 21 CFR 801 Subpart D) ☐ Over-The-Counter Use (21 CFR 801 Subpart C)

CONTINUE ON A SEPARATE PAGE IF NEEDED.

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FORM FDA 3881 (8/14)

Page 1 of 1 FDA

PSC Publishing Services (301) 443-6740 EF

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510(k) SUMMARY

ImpediMed's SOZO system

Submitter:

ImpediMed LimitedUnit 150 Parker CourtPinkenba Qld 4008Australia
Phone:	760 585 2104
Facsimile:	760 804 9245
Contact Person:	Reuben Lawson
Date Prepared:	July 13, 2017
Name of Device:	SOZO
Common or Usual Name:	Body Fluid Analyzer
Classification Name:	Impedance Plethysmograph
Regulatory Class:	21 CFR 820.2770
Product Code:	OBH
Predicate Devices	ImpediMed Limited's L-Dex® U400 (K130338)

Device Description

Intended Use/Indications for Use

A bioimpedance spectroscopy device for use on adult human patients, utilizing impedance ratios

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that are displayed as an L-Dex ratio that supports the measurement of extracellular fluid volume differences between the limbs and is presented to the clinician on an L-Dex scale as an aid to their clinical assessment of unilateral lymphedema of the arm and leg in women and the leg in men.

The device is only indicated for patients who will have or who have had lymph nodes, from the axillary and pelvic regions, either removed, damaged or irradiated.

Summary of Technological Characteristics

Bioimpedance spectroscopy is the technological principle for both the subject and predicate devices. The subject and predicate devices are based on the following same fundamental technological elements:

. Use of electrodes to take measurements; two 'drive' and two 'sense' channels are used to measure each side of the body;
. 'Drive' channels deliver very low levels of current (~200ua RMS) across 256 frequencies logarithmically spaced from 3kHz to 1000kHz;
. 'Sense' channels measure current (I), voltage (V) and phase angle (Ph), and calculates three bioimpedance parameters: impedance (Z), resistance (R) and reactance (Xc) to estimate extracellular fluid ratios, and calculate the impedance ratios which are converted to a L-Dex ratio:
Data is stored in and accessed from a local database (SOZOhub) utilizing separate software . installed on a network connected PC.

Minor technological differences exist between the subject and predicate devices:

. SOZO utilizes a revamped external housing, which is directly patient-contacting and uses stainless steel electrodes for taking bioimpedance measurements;
. SOZO is wall powered rather than battery powered;
. SOZO is controlled through an Android app on a supplied tablet, which is paired to the SOZO hardware over Bluetooth connection, and connects with the local database over Wi-Fi.

Purpose of 510(k)

The purpose of this 510(k) is to clear the design changes presented in the SOZO system.

These changes are intended to provide a faster, more streamlined customer experience with a more aesthetically pleasing design.

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Performance Data

The SOZO system has gone through appropriate testing per design controls to confirm the new design's functionality and performance.

Electrical safety/EMC: testing was performed according to the requirements set forth in IEC 60601 (subparts -1, -1-2, and -1-6). It was determined that the SOZO device meets electrical safety and EMC requirements, and CB certificate was granted for the system.

Software V&V: the same level of concern software documentation as the predicate device was created and testing performed in accordance with ISO 62304. The software was verified and validated to meet acceptance criteria and perform as intended.

Biocompatibility: testing was performed by an accredited third party according to the requirements set forth in ISO 10993 for a low risk, limited contact device. It was determined that the SOZO system passed biocompatibility testing with no failures reported.

Comparative performance vs. predicate device: using a test fixture to create multiple fixed impedance loads representing different 'humans', a SOZO system was compared against a U400 system to verify correlation in L-Dex readings. The SOZO system showed a very strong correlation (r > 0.99) compared to the cleared U400 system.

Functional performance: multiple SOZO systems were tested for design reliability by repeatedly placing weights on the components that encounter the most physical stress. Testing showed that the system is expected to remain functional throughout its intended life.

Conclusions

The SOZO system has the same intended uses /indications, and similar technological characteristics, and principles of operation as its predicate device. In addition, the minor technological differences between the SOZO system and its predicate device raise no new or different issues of safety or effectiveness. Design controls demonstrate that the SOZO system is as safe and effective as the cleared device version. Thus, the SOZO system is substantially equivalent.

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IX. PERFORMANCE STANDARDS

No performance standards or special controls have been developed under Section 514 of the FDC Act for a monitor of extracellular fluid (lymphedema) in an extremity. No special controls apply.

Consistent with FDA's guidance document entitled "Use of Standards in Substantial Equivalence Determinations' (March 12, 2000) and "Guidance for Industry and FDA Staff - Recognition and Use of Consensus Standards" (September 17, 2007), ImpediMed Limited is including this statement that the SOZO system complies with the following recognized consensus standards:

IEC 60601-1:2005/A1:2012 General Electrical and Mechanical Safety; ●
IEC 60601-1-2:2014 Ed4.0 Electromagnetic Compatibility; ●
IEC 60601-1-6:2010/A1:2013 Usability ●
EN/ISO 62304:2006 Medical device software Software life-cycle processes; ●
IEC 62366:2007/A1:2014 Application of usability engineering to medical devices;
ISO 10993-1:2009/TC1:2010 Biological Evaluation of Medical Devices;
ISO 10993-5:2009. Cytotoxicity: ●
ISO 10993-10:2010, Test for Irritation and Skin Sensitization.

A Data Standards Form (FDA Form 3654) is provided in Attachment 1 for each listed recognized consensus standard.

Regulation Number and Section

§ 870.2770 Impedance plethysmograph.

(a)
Identification. An impedance plethysmograph is a device used to estimate peripheral blood flow by measuring electrical impedance changes in a region of the body such as the arms and legs.(b)
Classification. Class II (special controls). The device, when it is a body composition analyzer which is not intended to diagnose or treat any medical condition, is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 870.9.