SynthAFax APTT Reagent is intended for the two-stage activated partial thromboplastin time (APTT) test, specific factor assays, APTT substitution test and monitoring heparin therapy.

Device Description

SynthAFax APTT Reagent is a liquid buffered reagent which contains a blend of synthetic phospholipids formed in liposomes, and a soluble plasma activator, ellagic acid, for optimal activation of the contact phase of coagulation. The use of synthetic phospholipids assures uniformity in the reagent and lot-to-lot consistency.

The activated partial thromboplastin time (APTT) test uses an activating agent and a phospholipid source and calcium to optimally activate the intrinsic pathway of coagulation. SynthAFax is incubated with an anticoagulated plasma sample for a standard period of time, known as the contact activation time (CAT). SynthAFax initiates the contact phase of coagulation through the activation of Factor XII. The addition of calcium chloride allows for the binding of other coagulation factors to the phospholipid and subsequent activation of the coagulation cascade. The generation of thrombin eventually cleaves fibrinogen and activates Factor XIII which crosslinks the fibrin molecules to form a visible clot. This occurs within a specified period of time.

If there is a coagulation factor deficiency in the intrinsic pathway, the time required for the formation of the clot will be prolonged beyond that expected for normal plasma. There will also be a prolongation of clotting caused by the presence of an inhibitor or the anticoagulant effect of heparin.

AI/ML Overview

Here's a breakdown of the acceptance criteria and the study proving the device meets them, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria are generally implied to be "equivalence" or "acceptable correlation" when compared to the predicate device, Activated THROMBOFAX. The specific numerical targets are not explicitly stated as pre-defined criteria but are demonstrated by the results achieving high correlation coefficients and comparable precision/sensitivity.

Acceptance Criteria (Implied)	Reported Device Performance (SynthAFax APTT Reagent)
Precision: Comparable to predicate device across various instruments and control levels (Low %CV for replicates, run-to-run, and between-day).	TABLE 1: Precision Data. Replicate %CV ranged from 0.7-1.1%, Run to Run %CV from 0.6-1.3%, and Between Day %CV from 0.3-1.1% across all instruments and control levels. These values are highly comparable to those reported for Act. THROMBOFAX, which ranged from 0.4-1.2% for Replicate %CV, 0.6-1.4% for Run to Run %CV, and 0.5-1.2% for Between Day %CV. This demonstrates clear comparable precision.
Correlation with Predicate Device: Acceptable correlation (e.g., high correlation coefficient) for clotting times across normal and abnormal plasma samples.	Koagulab 60-S: Correlation coefficient = 0.951. Slope = 1.08 (indicating slightly more sensitivity). ELECTRA 1600C: Correlation coefficient = 0.945. Slope = 1.15 (indicating slightly more sensitivity). Both are described as "acceptable correlation." (See Figure 1 and 2 descriptions).
Factor Assay Standard Curve Responsiveness: Equivalent responsiveness and acceptable correlation (e.g., high correlation coefficient) for coagulation factors (VIII, IX, XI, XII).	Koagulab 60-S: Factor curve responsiveness was equivalent for Factors VIII, IX, XI, and XII compared to Activated THROMBOFAX. All standard curves had correlation coefficients of 0.986 or better. ELECTRA 1600C: Factor curves had correlation coefficients of 0.995 or better. This indicates excellent correlation and equivalent responsiveness.
In Vitro Heparin Sensitivity: Equivalent sensitivity to heparinized plasma samples, as indicated by comparable slopes of heparin response curves.	Koagulab 60-S: Slopes of heparin response curve were equivalent (SynthAFax: 113.9 vs. Activated THROMBOFAX: 119.0). Correlation coefficients: 0.995 (SynthAFax) and 0.997 (Activated THROMBOFAX). ELECTRA 1600C: Slopes were also equivalent (SynthAFax: 86.9 vs. Activated THROMBOFAX: 92.5). Correlation coefficients: 0.999 (SynthAFax) and 0.997 (Activated THROMBOFAX). This confirms equivalent sensitivity. (See Figure 2 description, page 6).

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

Precision Study:
- Sample Size: For each OPCC level (I, II, III), across four instruments and two reagents, there were:
  - Grand Mean: n=180 (presumably 30 runs x 3 replicates/run x 2 days, or similar, as other n values add up to 180 total measurements from precision data).
  - Replicate %CV: n=90
  - Run to Run %CV: n=30
  - Between Day %CV: n=5
  - The samples used were commercial control plasmas: ORTHO® Plasma Coagulation Control (OPCC) Level I (normal), II and III (abnormal).
- Data Provenance: The study was performed at Ortho Diagnostic Systems, Inc., Raritan, NJ, USA. It is prospective data collection for the controls.
Reagent Correlation Study:
- Sample Size:
  - 100 fresh normal donor plasma samples.
  - 79 frozen abnormal plasma samples (from 41 patients on heparin, 11 patients on oral anticoagulants, 3 patients with liver disease, and 24 lupus anticoagulant patients).
- Data Provenance: Not explicitly stated, but given the location of Ortho Diagnostic Systems, Inc. (Raritan, NJ), it is highly likely that these were collected in the USA. The samples were a mix of "fresh normal donor plasma samples" and "frozen abnormal plasma samples," suggesting a blend of prospective and retrospective collection, though this is not explicitly detailed.
Factor Assay Standard Curves:
- The sample size for generating these curves is not explicitly stated, but it involves dilutions of specific factor-deficient plasmas or calibrated factor activity levels.
In Vitro Heparin Sensitivity:
- Sample Size: A fresh normal plasma pool consisting of 10 normal donors was used. Dilutions were made to achieve 0 to 0.5 units/ml of heparin.
- Data Provenance: Not explicitly stated, but likely from the same location as the other studies (USA).

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

This type of study (comparative performance of an in-vitro diagnostic reagent) does not typically involve human experts establishing "ground truth" in the way an imaging AI study would. The "ground truth" here is the measurement obtained by the predicate device (Activated THROMBOFAX® Reagent-Optimized), which is an established method for APTT determination. There were no human experts classifying outputs that required adjudication.

4. Adjudication Method for the Test Set

Not applicable. This is a quantitative reagent comparison study, not a study involving human interpretation that would require adjudication. The performance is measured directly by clotting times and statistical correlation.

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

No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not done. This type of study is relevant for imaging or diagnostic tasks where human readers interpret results, and the AI's impact on human performance is assessed. This submission concerns the analytical performance of an in-vitro diagnostic reagent.

6. Standalone (Algorithm Only Without Human-in-the-Loop Performance)

Yes, the studies conducted are standalone performance studies of the SynthAFax APTT Reagent. The reagent's performance is measured directly (e.g., clotting times, precision, correlation coefficients) and compared to the predicate device, or demonstrated through its own intrinsic capabilities (e.g., generating standard curves). There is no "human-in-the-loop" aspect to these performance evaluations as the device is for automated laboratory analysis.

7. Type of Ground Truth Used

The "ground truth" for this device's performance evaluation is primarily its concurrence and equivalence with a legally marketed predicate device (Activated THROMBOFAX® Reagent-Optimized), which has established analytical performance for APTT determination.

For precision, the ground truth is the inherent variability of the measurements themselves, evaluated against typical acceptable CVs for such assays and, more directly, against the predicate.
For correlation, the ground truth is the result obtained by the predicate device on the same samples.
For factor assays and heparin sensitivity, the "ground truth" is the known concentration or activity of the analytes (factors, heparin) in the prepared samples, and the comparison is again made against the responsiveness of the predicate device.

8. Sample Size for the Training Set

This submission does not discuss a "training set" in the context of machine learning. The device is a chemical reagent, not an AI/ML algorithm that requires training data. The "development" of the reagent would involve chemical formulation and optimization, not data-driven training.

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

Not applicable, as there is no "training set" in the machine learning sense for this device.

Summary

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K455638

510(k) SUMMARY

APR 2 3 1996

SUBMITTER:	Ortho Diagnostic Systems Inc.1001 U.S. Hwy 202Raritan, NJ 08869-0606	CONTACT:	Ms. Blanche ChienTel: (908) 704-3920Fax: (908) 218-8168
DEVICE NAME:	SynthAFax™APTT Reagent	PREDICATE:	ActivatedTHROMBOFAX®Reagent-Optimized
DATE:	December 8, 1995

DEVICE DESCRIPTION:

If there is a coagulation factor deficiency in the intrinsic pathway, the time required for the formation of the clot will be prolonged beyond that expected for normal plasma. There

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will also be a prolongation of clotting caused by the presence of an inhibitor or the anticoagulant effect of heparin.

INTENDED USE:

SynthAFax APTT Reagent is intended for the two-stage activated partial thromboplastin time (APTT) test, specific factor assays, APTT substitution test and monitoring heparin therapy.

TECHNOLOGICAL CHARACTERISTICS:

Both SynthAFax APTT Reagent and the predicate, Activated THROMBOFAX are used for activated partial thromboplastin time determinations for which they are well correlated and have equivalent precision. Both reagents are sensitive to plasma coagulation Factors I, II, V, VIII, IX, X, XI, XII, Prekallikrein, Kininogen, and acquired factor deficiencies cause by disseminated intravascular coagulation and liver disease. Both reagents are equally sensitive to lupus anticoagulants and to the anticoagulant effects of heparin therapy.

SynthAFax APTT Reagent is prepared from synthetic phospholipids of a consistent fatty acid make up and a known amount of each type of phospholipid. Activated THROMBOFAX is prepared from a phospholipid mixture extracted from bovine brain tissue and has a variety of fatty acid chain lengths and proportion of unsaturation.

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PERFORMANCE DATA:

Precision Study

The performance of SynthAFax APTT Reagent was evaluated at Ortho Diagnostic Systems, Inc., Raritan, NJ. The following data were derived from precision studies performed using both SynthAFax and Activated THROMBOFAX APTT Reagents and tested with ORTHO® Plasma Coagulation Control (OPCC) Level I (normal control), II and III (abnormal controls). The precision was tested on four different instruments to show the reagent equivalence independent of the instrument system.

TABLE 1: Precision Data

OPCC Level I	Koagulab 60S		ELECTRA 1600		ELECTRA 1400		ELECTRA 1000
	SynthAFax	Act. Throm.	SynthAFax	Act. Throm.	SynthAFax	Act. Throm.	SynthAFax	Act. Throm.
Grand Mean (sec.)(n=180)	25.0	24.5	22.7	22.7	22.4	23.0	23.0	22.9
Replicate %CV(n=90)	0.9	0.5	0.8	0.4	0.7	0.5	0.8	0.5
Run to Run %CV(n=30)	0.8	1.2	0.6	0.6	0.8	1.0	0.8	0.8
Between Day %CV(n=5)	0.6	0.5	0.3	0.5	0.8	0.6	0.7	0.7
OPCC Level II	Koagulab 60S		ELECTRA 1600		ELECTRA 1400		ELECTRA 1000
	SynthAFax	Act. Throm.	SynthAFax	Act. Throm.	SynthAFax	Act. Throm.	SynthAFax	Act. Throm.
Grand Mean (sec.)(n=180)	41.4	46.6	36.2	40.5	36.0	41.6	36.5	40.5
Replicate %CV(n=90)	0.9	0.6	0.8	0.5	0.7	0.4	0.7	0.7
Run to Run %CV(n=30)	1.1	1.4	0.6	0.7	1.1	1.1	1.1	1.0
Between Day %CV(n=5)	0.8	1.2	0.4	0.5	1.1	0.7	0.8	0.8
OPCC Level III	Koagulab 60S		ELECTRA 1600		ELECTRA 1400		ELECTRA 1000
	SynthAFax	Act. Throm.	SynthAFax	Act. Throm.	SynthAFax	Act. Throm.	SynthAFax	Act. Throm.
Grand Mean (sec.)(n=180)	54.5	61.9	47.9	53.4	47.2	53.4	46.9	54.3
Replicate %CV(n=90)	1.1	0.6	1.0	0.5	0.9	0.5	0.9	0.6
Run to Run %CV(n=30)	1.2	1.0	0.9	0.8	1.1	1.0	1.3	0.9
Between Day %CV(n=5)	0.9	0.9	0.7	0.5	1.1	0.6	1.0	0.8

SynthAFax versus Activated THROMBOFAX APTT Reagent

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Reagent Correlation Study

A total of one hundred (100) fresh normal donor plasma samples and seventy nine (79) frozen abnormal plasma samples from forty one (41) patients on heparin therapy, eleven (11) patients on oral anticoagulant therapy, three (3) patients with liver disease, and twenty four (24) lupus anticoagulant patients were tested for APTT with both SynthAFax and Activated THROMBOFAX APTT Reagents, using the KoaguLab 60-S Coagulation System and the ELECTRA 1600C. Data are shown in Figures 1 and 2 on the following page. For the KoaguLab 60-S, the correlation coefficient was 0.951, indicating acceptable correlation between the two reagents. The slope of the regression line was 1.08 indicating slightly more sensitivity for SynthAFax as compared to Activated THROMBOFAX APTT reagent. Similar results were seen on the ELECTRA 1600C.

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Image /page/4/Figure/0 description: The image contains two scatter plots comparing SynthAFax Clotting Times versus Activated THROMBOFAX Clotting Times. Figure 1 shows the correlation studies for Koagulab 60-S, with a correlation coefficient of 0.951, a slope of 1.08, and an intercept of -0.4. Figure 2 shows the correlation studies for ELECTRA 1600, with a correlation coefficient of 0.945, a slope of 1.15, and an intercept of -2.0. Both plots show a positive correlation between the two clotting time measurements, with data points representing patient samples.

Data From Reagent Correlation Studies

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Factor Assay Standard Curves

Factor VIII, IX, XI and XII Assay Standard Curves were performed with SynthAFax and Activated THROMBOFAX APTT Reagents on both the KoaguLab 60-S Coagulation System and ELECTRA 1600C. On the KoaguLab 60-S, the factor curve responsiveness was equivalent for Factors VIII, IX, XI, and XII compared to Activated THROMBOFAX, and all standard curves had correlation coefficients of 0.986 or better, indicating acceptable correlation. Factor curves on the ELECTRA 1600C analyzer were fit with third order polynomial regressions and all gave correlation coefficients of 0.995 or better.

		Koagulab 60-S		ELECTRA 1600C
		ORTHOSynthAFax	ActivatedTHROMBOFAX	ORTHOSynthAFax	ActivatedTHROMBOFAX
Factor VIII	Slope	-0.130	-0.108
	Y-Intercept	1.823	1.829
	Corr. Coef.	0.988	0.995	1.000	0.997
Factor IX	Slope	-0.129	-0.104
	Y-Intercept	1.803	1.820
	Corr. Coef.	0.994	0.986	1.000	0.998
Factor XI	Slope	-0.173	-0.173
	Y-Intercept	1.996	1.996
	Corr. Coef.	0.997	0.995	0.997	0.995
Factor XII	Slope	-0.239	-0.288
	Y-Intercept	2.021	2.215
	Corr. Coef.	0.994	0.995	0.999	0.998

Data From Factor Assay Standard Curves

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In Vitro Heparin Sensitivity

The in vitro heparin sensitivity for SynthAFax and Activated THROMBOFAX APTT reagents was determined by performing a heparin response curve on the KoaguLab 60-S and ELECTRA 1600C using heparinized plasma dilutions at 0 to 0.5 units/ml. Heparin was added at the appropriate levels to a fresh normal plasma pool consisting of 10 normal donors. The slopes of the in vitro heparin response curve were equivalent for SynthAFax (113.9) and Activated THROMBOFAX (119.0) on the Koagulab 60-S, indicating equivalent sensitivity to heparinized plasma samples. On the ELECTRA 1600C the slopes were also equivalent for SynthAFax (86.9) and Activated THROMBOFAX (92.5)

Image /page/6/Figure/2 description: The image contains two line graphs comparing the clotting time versus Heparin concentration for two different devices, Koagulab 60-S and ELECTRA 1600C. Each graph plots two lines representing 'Activated THROMBOFAX' and 'SynthAFax'. For Koagulab 60-S, the slopes are 119.0 and 113.9 with correlation coefficients of 0.997 and 0.995, respectively, while for ELECTRA 1600C, the slopes are 92.5 and 88.9 with correlation coefficients of 0.999 and 0.997, respectively.

In Vitro Heparin Curves

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CONCLUSION

SynthAFax APTT Reagent is substantially equivalent to Activated THROMBOFAX Reagent-Optimized currently in commercial distribution by Ortho Diagnostic Systems Inc. as an activated partial thromboplastin time reagent used to determine deficiencies of clotting factor activity, either hereditary or acquired, in the intrinsic coagulation pathway or to monitor the effect of anticoagulant therapy.

Regulation Number and Section

§ 864.7925 Partial thromboplastin time tests.

(a)
Identification. A partial thromboplastin time test is a device used for primary screening for coagulation abnormalities, for evaluation of the effect of therapy on procoagulant disorders, and as an assay for coagulation factor deficiencies of the intrinsic coagulation pathway.(b)
Classification. Class II (performance standards).