The IDS-iSYS Intact PTH+ assay is an in vitro diagnostic device intended for the quantitative determination of intact PTH in human serum or plasma on the IDS-iSYS Multi-Discipline Automated System. Results are to be used in the differential diagnosis of hypercalcemia and hypocalcemia resulting from disorders of calcium metabolism.

Device Description

The IDS-iSYS Intact PTH" assay is based on chemiluminescence technology. 100 uL of patient sample is incubated with a biotinylated polyclonal anti-PTH (39-84) antibody and an acridinium labelled PTH (13-34) antibody. Streptavidin labelled magnetic particles are added prior to a second incubation step. The magnetic particles are captured using a magnet and a wash step performed to remove any unbound analyte. Trigger reagents are added; the resulting light emitted by the acridinium label is directly proportional to the concentration of Intact PTH in the original sample.

IDS-iSYS Intact PTH reagent kit consists of one (1) Immunoassay Cartridge, two (2) vials each of 2 concentration Calibrator levels and a mini-CD containing the Instructions For Use (IFU), CRY files and Certificate of Analysis.

IDS-iSYS Intact PTHN Cartridge, sufficient for 100 tests, consists of reagents provided in individual compartment within a plastic container called the Cartridge. The IDS-iSYS Intact PTHN Cartridge contains the following ready to use reagents:

· Magnetic particles coated with streptavidin in a phosphate buffer containing sodium azide as preservative (<0.1%), 1 bottle.
Goat polyclonal antibody against 13-34 PTH labelled with an acridinium ester derivative, in buffer containing goat serum with sodium azide as preservative (<0.1%), 1 bottle.
Goat polyclonal antibody against 39-84 PTH 1abelled with biotin, in buffer containing bovine and goat proteins with sodium azide as preservative (<0.1%), 1 bottle.

IDS-iSYS Intact PTH Calibrators are included in the reagent kit.

· Calibrator A: Two vials of lyophilized porcine serum matrix buffer containing low level PTH and sodium azide as preservative >1% (w/w%).
· Calibrator B: Two vials of lyophilized porcine serum matrix buffer containing high level PTH and sodium azide as preservative >1% (w/w%).

The submission is due to a new source of antibody for the assay.

AI/ML Overview

This document describes the performance characteristics of the IDS-iSYS Intact PTHN assay, an in vitro diagnostic device for quantitative determination of intact PTH.

Here's an analysis of the acceptance criteria and study information provided:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria are not explicitly stated as distinct numerical targets but are implicitly defined by the reported performance and the comparison to the predicate device. The information below summarizes the performance characteristics provided, which in a regulatory context, demonstrate the device meets its intended use and is substantially equivalent to the predicate.

Performance Characteristic	Predicate Device (K103325) Performance	Candidate Device (IDS-iSYS Intact PTHN) Performance	Implied Acceptance Criteria (Demonstrated)
Method Comparison (against a commercially available method)	N/A	n=312 samples; Slope: 1.02 (95% CI: 0.99 to 1.04); Intercept: -0.7 pg/mL (95% CI: -5.4 to 4.1); Correlation coefficient (r): 1.00	Demonstrate strong correlation and agreement with a commercially available quantitative chemiluminescence Intact PTH assay (e.g., r close to 1, slope close to 1, intercept close to 0) as per CLSI EP-9A2 guidelines.
Sample Matrix Comparison (vs. K2 EDTA plasma)	N/A
- Serum (Red Top)	N/A	n=52; Slope: 0.94 (95% CI: 0.92 to 0.97); Intercept: 2.55 (95% CI: 0.86 to 3.16); r: 1.00	Demonstrate acceptable agreement across different sample matrices (serum, lithium heparin plasma) compared to the control (K2 EDTA plasma) as per CLSI EP9-A3 guidelines. Slopes close to 1 and intercepts close to 0 with good correlation coefficients.
- Serum (SST)	N/A	n=52; Slope: 0.93 (95% CI: 0.91 to 0.96); Intercept: 2.38 (95% CI: 1.25 to 3.15); r: 1.00
- Lithium Heparin	N/A	n=52; Slope: 0.98 (95% CI: 0.95 to 0.99); Intercept: 0.42 (95% CI: -0.43 to 1.63); r: 1.00
Reference Interval	11.5 to 78.4 pg/mL	10.3 to 80.5 pg/mL	Establish a 95% reference interval for a healthy population, consistent with clinical expectations and CLSI C28-A3 guidelines. The new range should be comparable to the predicate.
Sensitivity
- Limit of Blank (LoB)	1.2 pg/mL	0.9 pg/mL	Demonstrate low limits of blank, detection, and quantitation, indicating the ability to detect very low concentrations of PTH, as per CLSI EP17-A guidelines. Should be comparable or better than the predicate.
- Limit of Detection (LoD)	2.5 pg/mL	2.3 pg/mL
- Limit of Quantitation (LoQ)	4.5 pg/mL	4.5 pg/mL
Precision
- Within-run CV%	1.1% to 6.3%	1.5% to 9.9%	Demonstrate consistent and reproducible results across different concentration levels, within acceptable ranges for clinical diagnostic assays, as per CLSI EP-5A2 guidelines. Total CV should be within acceptable limits (e.g., <10-15% depending on concentration).
- Total CV%	4.1% to 8.2%	1.8% to 9.9%
Linearity
- K2 EDTA Plasma	$y = 1.002 x – 4.748; R^2 = 1.00$	$y = 0.96 x − 0.1; R^2 = 1.00$	Demonstrate linearity across the claimed measurement range (5 to 3500 pg/mL) with a regression coefficient ($R^2$) close to 1 and minimal deviation from expected values, as per CLSI EP-6A guidelines.
- Serum	N/A (Only K2 EDTA provided for predicate)	$y = 1.02x – 0.2; R^2 = 1.00$
High Dose Hook Effect	Not observed up to 95,000 pg/mL	Not observed up to 100,000 pg/mL	No significant hook effect should be observed within a clinically relevant and extended high concentration range to prevent falsely low results in patients with very high PTH levels. The demonstrated range should be comparable or wider than the predicate.
Interferences (≤±10% bias)
- Bilirubin, conjugated	N/A	22 mg/dL	No significant interference (≤±10% bias) from common endogenous and exogenous interfering substances at clinically relevant concentrations, as per CLSI EP7-A2 guidelines. The tested concentrations should be comparable or improved compared to the predicate device.
- Bilirubin, unconjugated	20 mg/dL	40 mg/dL
- Biotin	300 nmol/L	300 nmol/L
- Cholesterol	N/A	395 mg/dL
- HAMA	1000 ng/mL	1000 ng/mL
- Hemoglobin	250 mg/dL	500 mg/dL
- Rheumatoid Factor	1500 IU/mL	1836 IU/mL
- Total Protein	N/A	10 g/dL
- Triglycerides	3000 mg/dL	3000 mg/dL
- Acetaminophen	N/A	200 µg/mL
- Carbamazepine	N/A	200 µg/mL
- Ibuprofen	N/A	500 µg/mL
Cross-Reactivity (vs. PTH (1-84))
- PTH (1-84)	100%	100%	Demonstrate high specificity to intact PTH (1-84) and minimal cross-reactivity with PTH fragments or structurally similar proteins, improving upon the predicate where possible, as per CLSI EP7-A2 guidelines.
- PTH (7-84)	60%	83.6%
- PTH (1-34)	0.5%	<0.01%
- PTH (39-84)	Not detectable	<0.01%
- PTH (53-84)	2%	<0.01%
- PTH (39-68)	N/A	<0.01%
- PTH (44-68)	2%	<0.01%
- Human Calcitonin	4%	<0.01%
- CTX-1 (β CrossLaps)	2%	<0.01%
- Osteocalcin	2%	<0.01%

2. Sample Sizes and Data Provenance for Test Sets

Method Comparison:
- Sample Size: 312 serum samples (291 native, 21 spiked).
- Data Provenance: Not explicitly stated but clinical samples are generally considered prospective or retrospective from a clinical laboratory setting. The use of "commercially available quantitative chemiluminescence Intact PTH assay" as the comparator suggests real-world clinical samples.
Sample Matrix Comparison:
- Sample Size: 52 matched samples (45 native, 7 spiked).
- Data Provenance: Not explicitly stated, but clinical samples are typically used for this type of evaluation.
Reference Interval:
- Sample Size: 129 individuals (67 males, 62 females; 21 to 89 years of age).
- Data Provenance: K2 EDTA plasma samples collected from individuals with normal calcium, phosphate, and TSH values from the north, central and south regions of the United States. This is prospective or a well-characterized retrospective collection.
Sensitivity (LoB, LoD, LoQ):
- Sample Size: 60 blanks and 10 low-level serum samples.
- Data Provenance: Lab-prepared samples and low-level serum samples, likely from internal or commercially acquired biobanks.
Precision:
- Sample Size: 7 samples (tested multiple times, N=80 for each sample).
- Data Provenance: Lab-prepared controls and potentially pooled clinical samples ("Serum Sample," "EDTA Plasma Sample").
Linearity:
- Sample Size: Not explicitly stated as a single number, but involved diluting high patient samples with low patient samples. Each sample was measured in 4 replicates.
- Data Provenance: High and low intact PTH human K2 EDTA plasma and serum samples.
High Dose Hook Effect:
- Sample Size: 3 samples (1 EDTA Plasma, 2 Serum) per spiked concentration.
- Data Provenance: Spiked samples, likely from a laboratory setting using clinical matrices.
Interferences:
- Sample Size: Two K2-EDTA samples (low and high Intact PTH levels) and two serum samples (different Intact PTH concentrations).
- Data Provenance: Spiked samples, using clinical matrices (K2-EDTA and serum).
Cross-Reactivity:
- Sample Size: A serum sample and a zero calibrator matrix.
- Data Provenance: Spiked samples, using clinical serum matrix.

3. Number of Experts and Qualifications for Ground Truth

This device is an in vitro diagnostic assay, where the "ground truth" for performance characteristics such as sensitivity, precision, linearity, and interference is established by:

Reference Methods: Comparison against established, commercially available, and often FDA-cleared or gold-standard assays (e.g., the predicate device or a "commercially available quantitative chemiluminescence Intact PTH assay" for method comparison).
Analytical Standards/Spikes: Precisely known concentrations of analyte or interfering substances are used to create "spiked" samples, where the "true" concentration is known by design.
Clinical Laboratory Standard Institute (CLSI) Guidelines: Adherence to these guidelines (EP-9A2, EP9-A3, C28-A3, EP17-A, EP-5A2, EP-6A, EP7-A2) dictates the experimental design and statistical analysis which are considered "best practice" for establishing performance characteristics in IVDs.

There are no "experts" in the sense of physicians or radiologists directly assessing images or patient data to establish ground truth for this type of analytical device performance. The "ground truth" is analytical and derived from established laboratory practices and reference methods.

4. Adjudication Method for the Test Set

Not applicable for this type of in vitro diagnostic device study. Adjudication methods like "2+1" or "3+1" are typically used in clinical studies, particularly for diagnostic imaging or subjective clinical assessments, where consensus among multiple expert readers is needed to establish a ground truth for a disease state. For IVD analytical performance, the ground truth is either the value from a reference method or a gravimetrically/volumetrically determined "true" concentration.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

No, an MRMC comparative effectiveness study was not done. This type of study is primarily relevant for diagnostic imaging AI algorithms where multiple human readers interpret cases with and without AI assistance. This document describes an in vitro diagnostic assay for a biochemical marker, not an imaging device or an AI application that assists human interpretation.

6. Standalone Performance

Yes, the studies described are standalone performance assessments of the IDS-iSYS Intact PTHN assay. The device is an automated system for measuring PTH levels, and the performance characteristics (method comparison, precision, linearity, etc.) directly evaluate the algorithm/assay's ability to accurately quantify PTH in patient samples. There is no human-in-the-loop component being evaluated in these tests; the device's output is directly compared to established analytical standards or reference methods.

7. Type of Ground Truth Used

Reference Method Results: For method comparison, the results from a "commercially available quantitative chemiluminescence Intact PTH assay" served as the ground truth comparator.
Assigned Values of Controls/Standards: For precision, linearity, sensitivity, interference, and cross-reactivity studies, the ground truth was based on:
- Known concentrations: Spiked samples with precisely known concentrations of analyte or interfering substances.
- Expected values: Derived from dilution series or preparation of controls.
- Blank matrices: For limit of blank determination.
Clinical Criteria: For the reference interval study, the ground truth for "normal" individuals was based on clinical criteria (normal calcium, phosphate, and TSH values).

8. Sample Size for the Training Set

The document does not specify a "training set" in the context of machine learning. This is an analytical medical device, not an AI/ML algorithm that is "trained" on data. The characteristics and parameters of the assay (e.g., antibodies, reagent concentrations, calibration curve algorithm) are developed and optimized during the product development phase, which is analogous to "training" in AI, but it's not described in terms of a distinct dataset.

9. How Ground Truth for the Training Set Was Established

As explained above, there isn't a "training set" in the common AI/ML sense. The "ground truth" for the development and optimization of the assay's chemical and instrumental parameters typically comes from:

Biochemical principles: Understanding of antigen-antibody interactions, chemiluminescence, and PTH biology.
Calibration materials: Use of international standards or highly characterized primary calibrators with assigned values.
Internal validation studies: Extensive testing during R&D to optimize reagent formulations, incubation times, and instrumental settings to achieve desired performance characteristics against known samples and reference methods.
Iterative development and testing: Performance data from pilot studies or earlier assay versions would inform adjustments to achieve acceptable analytical performance compared to the established medical consensus for PTH measurement.

Summary

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

IMMUNODIAGNOSTIC SYSTEMS LTD MICK HENDERSON REGULATORY AFFAIRS OFFICER 10 DIDCOT WAY BOLDON BUSINESS PARK BOLDON NE35 9PD, GREAT BRITAIN

January 31, 2017

Re: K161158

Trade/Device Name: IDS-iSYS Intact PTH® Regulation Number: 21 CFR 862.1545 Regulation Name: Parathyroid hormone test system Regulatory Class: II Product Code: CEW Dated: January 9, 2017 Received: January 11, 2017

Dear Mick Henderson:

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.

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 Parts 801 and 809); medical device reporting (reporting of medical device-related adverse events) (21 CFR 803); good manufacturing practice requirements as set forth in the quality systems (OS) regulation (21 CFR Part 820); and if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR 1000-1050.

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If you desire specific advice for your device on our labeling regulations (21 CFR Parts 801 and 809), 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 yours,

Katherine Serrano -S

For : Courtney H. Lias, Ph.D. Director Division of Chemistry and Toxicology Devices Office of In Vitro Diagnostics and Radiological Health Center for Devices and Radiological Health

Enclosure

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DEPARTMENT OF HEALTH AND HUMAN SERVICES Food and Drug Administration

Indications for Use

Form Approved: OMB No. 0910-0120 Expiration Date: January 31, 2017

510(k) Number (if known) K161158

Device Name IDS-iSYS Intact PTHN

Indications for Use (Describe)

IDS-iSYS Intact PTHN

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)
X

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510(k) SUMMARY IDS-iSYS Intact PTHN Assay

This summary of 510(k) safety and effectiveness information is submitted in accordance with the requirements of 21 CFR 807.92.

1.	510(k) Number:	K161158
2.	Submitter:	Immunodiagnostic Systems Ltd10 Didcot WayBoldon Business ParkBoldonTyne and WearNE35 9PDUnited Kingdom
3.	Contact Person:	Mick HendersonPhone: +44(0)191 5190660Fax: +44(0) 191 5190760Email: mick.henderson@idsplc.com
4.	Secondary Contact:	Heather PhamPhone: +1(480)-414-7175Fax: +44(0) 191 5190760Email: heather.pham@idsplc.com
5.	Date Prepared:	09 January 2017
6.	Proprietary and Established Name:IDS-iSYS Intact PTHN
7.	Regulatory Information:	Classification: 21CFR 862.1545Device Class Class IIProduct Code: CEWPanel: Clinical Chemistry (75)

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8. Device Descriptions:

· Magnetic particles coated with streptavidin in a phosphate buffer containing sodium azide as preservative (<0.1%), 1 bottle.
Goat polyclonal antibody against 13-34 PTH labelled with an acridinium ester derivative, in buffer containing goat serum with sodium azide as preservative (<0.1%), 1 bottle.
Goat polyclonal antibody against 39-84 PTH 1abelled with biotin, in buffer containing bovine and goat proteins with sodium azide as preservative (<0.1%), 1 bottle.

IDS-iSYS Intact PTH Calibrators are included in the reagent kit.

· Calibrator A: Two vials of lyophilized porcine serum matrix buffer containing low level PTH and sodium azide as preservative >1% (w/w%).
· Calibrator B: Two vials of lyophilized porcine serum matrix buffer containing high level PTH and sodium azide as preservative >1% (w/w%).

The submission is due to a new source of antibody for the assay.

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9. Predicate Devices:

IDS-iSYS Intact PTH, K103325

10. Special Conditions for Use:

For in vitro diagnostic use. Rx Only

11. Special instrument Requirements:

IDS-iSYS Multi-Discipline Automated System (K091849)

12. Intended Use:

The IDS-iSYS Intact PTHN assay is an in vitro diagnostic device intended for the quantitative determination of intact PTH in human serum or plasma on the IDS-iSYS Multi-Discipline Automated System. Results are to be used in the differential diagnosis of hypercalcemia and hypocalcemia resulting from disorders of calcium metabolism.

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13. Substantial Equivalence Information

A comparison of the similarities and differences between the modified IDS-iSYS Intact PTH® assay and the original IDS-iSYS Intact PTH assay (K103325) are provided in the following table:

Assay Similarities and Differences
Characteristics	Predicate DeviceIDS-iSYS Intact PTH(K103325)	Candidate DeviceIDS-iSYS Intact PTHN
Intended use	intended for the quantitativedetermination of PTH in humanserum or plasma.	Same
Measured analyte	Intact PTH	Same
Assay type	Chemiluminescenceimmunoassay	Same
Antibody	Goat polyclonala) anti- PTH (13-34)b) anti-PTH (39-84)	Same
Sample matrix	Plasma (K2-EDTA,lithium heparin) andserum	Same
Sample size	100 μL	Same
Samplehandling/processing	AutomatedIDS-iSYS Multi-DisciplineAutomated System	Same
Calibrator	2 levelsIncluded with kit	Same
Calibration interval	2 point calibration curve stablefor 21 days	2 point calibration curve stablefor 15 days
Reagent storage	On-board or at 2-8°C	Same
Measurement range	5 to 5000 pg/mL	5 to 3500 pg/mL
Reference interval	11.5 to 78.4 pg/mL	10.3 to 80.5 pg/mL
Assay Similarities and Differences
Characteristics	Predicate DeviceIDS-iSYS Intact PTH(K103325)	Candidate DeviceIDS-iSYS Intact PTHN
Interfering Substances
- Bilirubin, conjugated	N/A	22 mg/dL
- Bilirubin, unconjugated	20 mg/dL	40 mg/dL
- Biotin	300 nmol/L	Same
- Cholesterol	N/A	395 mg/dL
- HAMA	1000 ng/mL	Same
- Hemoglobin	250 mg/dL	500 mg/dL
- Rheumatoid Factor	1500 IU/mL	1836 IU/mL
- Total Protein	N/A	10 g/dL
- Triglycerides	3000 mg/dL	Same
- Acetaminophen	N/A	200 µg/mL
- Carbamazepine	N/A	200 µg/mL
- Ibuprofen	N/A	500 µg/mL
Specificity
- PTH (1-84)	100%	Same
- PTH (7-84)	60%	83.9%
- PTH (1-34)	0.5%	<0.01%
- PTH (39-84)	Not detectable	<0.01%
- PTH (53-84)	2%	<0.01%
- PTH (39-68)	N/A	<0.01%
- PTH (44-68)	2%	<0.01%
- Human Calcitonin	4%	<0.01%
- CTX-1 (β CrossLaps)	2%	<0.01%
- Osteocalcin	2%	<0.01%
Hook Effect	Not observed up to95,000 pg/mL	Not observed up to100,000 pg/mL
Sensitivity
- Limit of Blank (LoB)	1.2 pg/mL	0.9 pg/mL
- Limit of Detection (LoD)	2.5 pg/mL	2.3 pg/mL
- Limit of Quantitation (LoQ)	4.5 pg/mL	4.5 pg/mL
Precision	in the range of 13.3 to3807 pg/mL, n =80	in the range of 15.4 to2229 pg/mL, n =80
- Within-run	1.1% to 6.3%	1.5% to 9.9%
- Total	4.1% to 8.2%	1.8% to 9.9%
Linearity	$y = 1.002 x – 4.748;$$R^2 = 1.00$	K2 EDTA:$y = 0.96 x − 0.1; R^2 = 1.00$Serum:$y = 1.02x – 0.2; R^2 = 1.00$

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14. Performance Characteristics

Method Comparison:

The IDS-iSYS Intact PTH" Assay was compared against a commercially available quantitative chemiluminescence Intact PTH assay, following CLSI EP-9A2, "Method Comparison and Bias Estimation Using Patient Samples". A total of 312 serum samples (291 native, 21 spiked), selected to represent a wide range of Intact PTH concentrations [6.3 - 3378.4 pg/mL], was assayed by each method. Deming regression analysis was performed on the comparative data:

n	Slope	95% CI	Intercept(pg/mL)	95% Cl	Correlation coefficient(r)
312	1.02	0.99 to 1.04	-0.7	-5.4 to 4.1	1.00

Sample Matrix:

The matrix comparison study was performed to evaluate the difference across tube types [serum without additive (red top), serum in separator tubes (SST), and lithium heparin plasma] versus the control samples (K2 EDTA plasma) following the CLSI EP9-A3 guideline. A total of 52 samples (45 native, 7 spiked) matched samples with Intact PTH concentrations ranging from of 10.6 to 2759.0 pg/mL were tested with the IDS-iSYS Intact PTH assay. Passing-Bablok regression analysis was performed on the comparative data:

Sample Type	n	Slope	95% Cl.	Intercept (pg/mL)	95% Cl.	Corr. Coeff. (r)
Serum (Red Top)	52	0.94	0.92 to 0.97	2.55	0.86 to 3.16	1.00
Serum (SST)	52	0.93	0.91 to 0.96	2.38	1.25 to 3.15	1.00
Lithium Heparin	52	0.98	0.95 to 0.99	0.42	-0.43 to 1.63	1.00

The type of specimen used (serum, EDTA plasma, or Lithium Heparin plasma) may influence PTH measurement. During routine monitoring of PTH levels, use the same specimen type throughout the monitoring period to avoid bias in the results.

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Reference Interval:

The 95% reference interval for the following group was calculated by a nonparametric method following the CLSI C28-A3, "How to Define and Determine Reference Intervals in the Clinical Laboratory". The K2 EDTA plasma samples were collected from 129 individuals (67 males, 62 females; 21 to 89 years of age) with normal calcium, phosphate, and TSH values from the north, central and south regions of the United States.

No. of subjects	129
Mean (pg/mL)	35.4
SD (pg/mL)	16.6
Median (pg/mL)	32.7
Reference Interval (pg/mL)	10.3 to 80.5

The above ranges should be considered as guidelines only; it is recommended that each laboratory establish its own expected range based upon its own patient population.

Sensitivity

The limit of blank (LoB), limit of detection (LoD) and limit of quantitation (LoQ) were determined with guidance from CLSI EP17-A, "Protocols for Determination of Limits of Detection and Limits of Quantitation" using 60 blanks and 10 low level serum samples. The following limits were determined with the IDS-iSYS Intact PTH™ Assay:

Sensitivity	Concentration (pg/mL)
Limit of Blank (LoB)	0.9
Limit of Detection (LoD)	2.3
Limit of Quantitation (LoQ)	4.5

Precision:

Precision testing was evaluated in accordance with a modified protocol based on CLSI EP-5A2, "Evaluation of Precision Performance of Quantitative Measurement Methods''. Seven (7) samples were assayed using one lot of reagent in duplicate twice per day for 20 days on one System.

		Mean	Within run		Total
Sample	n	(pg/mL)	SD	CV%	SD	CV%
Serum Sample 1	80	15.4	0.5	6.1	1.0	6.7
EDTA Plasma Sample 1	80	17.9	1.8	9.9	1.8	9.9
EDTA Plasma Sample 2	80	73.7	1.3	1.7	2.3	3.2
EDTA Plasma Sample 3	80	337.9	5.1	1.5	6.2	1.8
EDTA Plasma Sample 4	80	765.1	13.7	1.8	16.4	2.1
EDTA Plasma Sample 5	80	1376.6	20.4	1.5	40.7	3.0
EDTA Plasma Sample 6	80	2229.1	35.2	1.6	58.6	2.6

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Linearity:

Linearity was evaluated based on CLSI EP-6A, "Evaluation of the Linearity of Quantitative Measurement Procedures: A Statistical Approach". Samples were prepared by diluting a high patient sample with a low patient sample prior to assay. High intact PTH human K2 EDTA plasma and serum samples were diluted with low samples prior to assay. Each sample was measured in 4 replicates.

The K2 EDTA plasma samples with Intact PTH concentration levels above 80 pg/mL show a maximum -8.8 % deviation from linearity; samples below 80 pg/mL show a maximum deviation of -6.1 pg/mL. The weighted linear regression of the Observed versus the Expected concentrations is:

Observed = 0.96 x (Expected) = 0.1 pg/mL Regression coefficient R2: 1.00

The serum samples with intact PTH concentration levels above 80 pg/mL show a maximum deviation from linearity of 5.1%. The samples below 80 pg/mL show a maximum deviation of 0.6 pg/mL. The weighted linear regression of the Observed versus the Expected concentrations is:

Observed = 1.02 x (Expected) = 0.2 pg/mL Regression coefficient R2: 1 .00

High Dose Hook Effect:

Testing was conducted to determine if the IDS-iSYS Intact PTH® assay is susceptible to artificially low results in the presence of very high levels of PTH (Hook Effect). Three samples (1 EDTA Plasma, 2 Serum) were spiked with 1-84 PTH to 5000 pg/mL, 25000 pg/mL, 50000 pg/mL, 75000 pg/mL and 100000 pg/mL. Each specimen was measured in four (4) replicates using 3 reagents lots.

No high dose hook effect was observed for Intact PTH concentrations measured up to 100000 pg/mL.

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Interferences:

Interference studies were performed in accordance with the CLSI EP7-A2, "Interference testing in clinical chemistry; approved guideline". Two K2-EDTA samples at a low and high Intact PTH levels were spiked with following potential interfering substances: Triglycerides, Hemoglobin, Bilirubin (conjugated and unconjugated), Red blood cells, Biotin, Acetaminophen, Ibuprofen and Carbamazepine.

Two serum samples at different Intact PTH concentrations were used to determine the potential interference of Total Protein.

% Interference was calculated using the formula below:

% Interference = (Mean conc. of spiked sample - mean conc. of un-spiked sample)
                            x100% Mean concentration of un-spiked sample

For Cholesterol (Total), Rheumatoid factor (Rf) and HAMA (human anti mouse antibodies), the interference was tested by recovery of Intact PTH from a high serum pool spiked into a serum sample with known interferent substance levels. % Recovery was calculated using the formula below:

Recovery value = Mean concentration of spiked - Mean concentration of un-spiked
                 (Recovery value / Expected recovery value) x 100
% Recovery = =

Following potential interference compounds were tested and found not to interfere significantly with the IDS-iSYS Intact PTH assay, based on the criteria of nonsignificant interference of ≤±10% bias between the test (spiked) and control (un-spiked) samples:

Potentially Interfering Agent	Highest concentration tested thatdemonstrated no significant interference
Bilirubin, conjugated	22 mg/dL
Bilirubin, unconjugated	40 mg/dL
Biotin	300 nmol/L
Cholesterol, total	395 mg/dL
Haemoglobin	500 mg/dL
Human Anti Mouse Antibody (HAMA)	1000 ng/mL
Rheumatoid Factor	1836 IU/mL
Total Protein	10 g/dL
Triglyceride	3000 mg/dL
Acetaminophen	200 µg/mL
Carbamazepine	200 µg/mL
Ibuprofen	500 µg/mL

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Cross Reactivity:

The potential cross-reacting substances studies were performed on the IDS-iS Y S Intact PTH" assay, based on CLSI EP-7A2. A serum sample and a zero calibrator matrix was spiked with the following substance human PTH fragments and structurally similar proteins at the concentration listed below. The cross reactivity was then determined using the following equation:

	% cross reactivity = (Mean conc. spiked sample - mean conc.un-spiked sample)
x100% Spike concentration

Analyte	Concentration tested(pg/mL)	Cross-Reactivity
PTH (1-84)	2,000	100%
PTH (7-84)	2,000	83.6%
PTH (1-34)	100,000	<0.01%
PTH (39-84)	100,000	<0.01%
PTH (53-84)	100,000	<0.01%
PTH (39-68)	100,000	<0.01%
PTH (44-68)	100,000	<0.01%
Human Calcitonin	100,000	<0.01%
CTX-1 (β CrossLaps)	100,000	<0.01%
Osteocalcin	100,000	<0.01%

15. Conclusions

The IDS-iSYS Intact PTH assay, after the modification in antibody source, is substantially equivalent in principle and performance to the originally submitted IDS-iSYS Intact PTH assay (K103325).

Regulation Number and Section

§ 862.1545 Parathyroid hormone test system.

(a)
Identification. A parathyroid hormone test system is a device intended to measure the levels of parathyroid hormone in serum and plasma. Measurements of parathyroid hormone levels are used in the differential diagnosis of hypercalcemia (abnormally high levels of calcium in the blood) and hypocalcemia (abnormally low levels of calcium in the blood) resulting from disorders of calcium metabolism.(b)
Classification. Class II.