Retrospective clinical plasma samples from patients with suspected VTE
The study evaluated the clinical performance (sensitivity, specificity, and negative predictive value) of the HemosIL AcuStar D-Dimer assay using 344 frozen clinical samples from patients presenting with suspected venous thromboembolism.
Patients admitted to an emergency unit with suspected PE or DVT; Sample Size: 344
Standard objective tests
Sensitivity, Specificity, NPV
Indications for Use
ACL AcuStar: Automated immunoassay analyzer designed specifically for in vitro diagnostic use in a clinical laboratory. The assay analysis is based on chemiluminescent technology. The system provides results for both direct measurements and calculated parameters. HemosIL AcuStar D-Dimer: Fully automated chemiluminescent immunoassay for the quantitative determination of D-Dimer in human citrated plasma on the ACL AcuStar as an aid in the diagnosis of venous thromboembolism (VTE) [deep vein thrombosis (DVT) and pulmonary embolism (PE)]. HemosIL AcuStar D-Dimer Controls: For the quality control of D-Dimer assay performed on the ACL AcuStar.
Device Story
ACL AcuStar is an automated, software-driven, bench-top chemiluminescent immunoassay analyzer for clinical laboratories. It processes human citrated plasma samples using magnetic particles coated with anti-D-Dimer monoclonal antibodies and isoluminol-labeled tracer antibodies. The system performs a two-step incubation and wash cycle, measuring relative light units (RLUs) via an internal luminometer. RLUs are proportional to D-Dimer concentration. The device includes a control computer for user interface, data management, and automated sample handling/dilution. Results assist clinicians in diagnosing venous thromboembolism (VTE). The system uses barcode readers for specimen identification and supports automated on-board dilutions to expand the reportable range.
Clinical Evidence
Clinical study evaluated 344 frozen citrated plasma samples from emergency unit patients suspected of VTE. 97 were VTE positive, 247 negative. Using a 500 ng/mL cut-off, the assay demonstrated 100% clinical sensitivity (95% CI 96.3-100.0%), 55.5% specificity (95% CI 49.0-61.8%), and 100% negative predictive value (95% CI 97.3-100.0%). Method comparison studies against VIDAS and ACL TOP predicates showed good correlation (r=0.89 to 0.98).
Technological Characteristics
Bench-top automated chemiluminescent immunoassay analyzer. Uses magnetic particle separation and isoluminol-labeled monoclonal antibody tracers. Dimensions/form factor: bench-top. Connectivity: barcode reader for specimen/rack identification. Software: automated, 4-parameter logistic curve (4PLC) data reduction. Sterilization: N/A (reagents). Materials: mouse monoclonal antibodies, magnetic particles, isoluminol tracer.
Indications for Use
Indicated for quantitative determination of D-Dimer in human citrated plasma to aid in diagnosis of venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE). For use in clinical laboratory settings.
Regulatory Classification
Identification
A multipurpose system for in vitro coagulation studies is a device consisting of one automated or semiautomated instrument and its associated reagents and controls. The system is used to perform a series of coagulation studies and coagulation factor assays.
Special Controls
*Classification.* Class II (special controls). A control intended for use with a multipurpose system for in vitro coagulation studies is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 864.9.
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# 510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION DECISION SUMMARY
A. 510(k) Number:
K083518
B. Purpose for Submission:
Clearance of a new instrument, assay, and controls
C. Measurand:
D-Dimer
D. Type of Test:
Quantitative, Chemiluminescent Immunoassay
E. Applicant:
Instrumentation Laboratories
F. Proprietary and Established Names:
ACL AcuStar
HemosIL AcuStar D-Dimer
HemosIL AcuStar D-dimer Controls
G. Regulatory Information:
1. Regulation section:
21 CFR 864.7320
2. Classification:
Class II
3. Product code:
JPA (Instrument)
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GGN (Controls)
DAP (Assay)
4. Panel:
81 Hematology
H. Intended Use:
1. Intended use(s):
ACL AcuStar is an automated immunoassay analyzer designed specifically for in vitro diagnostic use in a clinical laboratory. The assay analysis is based on chemiluminescent technology. The system provides results for both direct measurements and calculated parameters.
HemosIL AcuStar D-dimer is a fully automated chemiluminescent immunoassay for the quantitative determination of D-Dimer in human citrated plasma on the ACL AcuStar as an aid in the diagnosis of venous thromboembolism (VTE).
HemosIL AcuStar D-Dimer controls are for the quality control of D-dimer assay performed on the ACL AcuStar.
2. Indication(s) for use:
3. Special conditions for use statement(s):
4. Special instrument requirements:
ACL AcuStar
I. Device Description:
The ACL AcuStar is automated, software driven, bench-top analyzer consisting of (1) a main unit that provides sample and reagent handling, sample testing and result measurement hardware, and (2) a control computer that provides the user interface, data and instrument management.
The AcuStar D-Dimer Assay is a 100 determination kit consisting of 1 vial of a magnetic particle suspension coated with mouse monoclonal antibody directed against D-Dimer, 1 vial of tracer consisting of anti-XDP mouse monoclonal antibody labeled with isoluminol,
2
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diluent, buffers, perservative and stabilizers.
The AcuStar D-Dimer Controls are tri-level controls of partially purified D-Dimer obtained by digestion of Factor XIIIa cross-linked human fibrin with human plasmin.
## J. Substantial Equivalence Information:
1. Predicate device name(s):
- BioMerieux VIDAS Instrument
- BioMerieux VIDAS D-Dimer Exclusion Assay
- Instrumentation Laboratories ACL TOP
- Instrumentation Laboratories HemosIL D-Dimer HS
- Instrumentation laboratories HemosIL D-Dimer Controls
2. Predicate 510(k) number(s):
- K891385
- K040882
- K073377
- K070927
- K972696
3. Comparison with predicate:
- Predicate 1 – ACL TOP (K073377) with HemosIL D-Dimer HS (K070927) and HemosIL D-Dimer Controls (K972696)
- Predicate 2 – VIDAS Instrument (K8913850 with VIDAS Exclusion Assay (K040882)
Similarities
| Item | Device | Predicate 1 | Predicate 2 |
| --- | --- | --- | --- |
| Intended Use | Quantitative determination of D-Dimer | same | same |
| Sample | Citrate Plasma | Same | same |
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Differences
| Item | Device | Predicate 1 | Predicate 2 |
| --- | --- | --- | --- |
| Assay principle | Chemiluminescent | Immunoturbidometric | EIA with fluorescent detection |
| Detection Limit | 6.51 ng/ml | 21 ng/ml | 45 ng/mL |
| Cut-off | 500 ng/ml | 230 ng/ml | 500 ng/ml |
K. Standard/Guidance Document Referenced (if applicable):
EP05-A2: Evaluation of Precision Performance of Quantitative Measurement Methods; Approved Guideline, 2nd Ed., 08/20/2004
C28-A2: How to Define and Determine Reference Intervals in the Clinical Laboratory; Approved Guideline, 2nd Ed., 06/01/2000
EP07-A2: Interference Testing in Clinical Chemistry; Approved Guideline, 2nd Ed., 11/23/2005
EP09-A2: Method Comparison and Bias Estimation, 2nd Ed., 09/20/2002
L. Test Principle:
The ACL AcuStar D-Dimer Chemiluminescent Immunoassay is a 2-step assay. In the first step, assay buffer, magnetic particles coated with a monoclonal antibody specific to D-Dimer is mixed with a sample. Following an incubation, during which any D-Dimer in the sample is captured by the antibody coated particles. In part two, after a washing step which removes any unbound materials, a tracer, consisting of a monoclonal antibody specific to D-Dimer conjugated with isoluminol is added to the sample cuvette. During a short incubation, the tracer binds to any D-Dimer captured by the antibody coated particle. After a washing step to remove any unbound tracer, the sample cuvette is sent to the luminometer, and the chemiluminescent reaction is measured as relative light units (RLU's). The RLU's are directly proportional to the D-Dimer concentration in the sample.
M. Performance Characteristics (if/when applicable):
1. Analytical performance:
a. Precision/Reproducibility:
2 replicates per run, 2 runs per day, for 20 days (N=80 for each sample level) on 2
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different ACL AcuStar instruments.
| ACL AcuStar No. 1 | | | | | |
| --- | --- | --- | --- | --- | --- |
| Control Level | N | Mean ng/mL | CV% Within Run | CV% Between Run | CV% Total |
| Low D-dimer Control | 80 | 232 | 5.5 | 1.4 | 6.0 |
| High D-dimer Control | 80 | 875 | 2.2 | 3.4 | 4.6 |
| Very High D-Dimer Control | 80 | 8918 | 2.2 | 5.5 | 5.9 |
| D-Dimer Calibrator Level 1 | 80 | 362 | 2.9 | 2.9 | 4.9 |
| ACL AcuStar No. 2 | | | | | |
| --- | --- | --- | --- | --- | --- |
| Control Level | N | Mean ng/mL | CV% Within Run | CV% Between Run | CV% Total |
| Low D-dimer Control | 80 | 234 | 4.0 | 2.8 | 6.8 |
| High D-dimer Control | 80 | 841 | 2.3 | 2.9 | 4.9 |
| Very High D-Dimer Control | 80 | 8467 | 2.5 | 3.7 | 5.6 |
| D-Dimer Calibrator Level 1 | 80 | 358 | 2.7 | 3.1 | 5.4 |
# b. Linearity/assay reportable range:
Dilutions of a high concentration D-Dimer plasma sample ( $\sim 95000\mathrm{ng/mL}$ ) were prepared in AcuStar D-Dimer Assay Sample Diluent. Each level was tested in quadruplicate using two different lots of AcuStar D-dimer reagents. Results demonstrated linearity of $54.3 - 74000\mathrm{ng/mL}$ with Auto Rerun Off. When the Auto Rerun is activated, the ACL AcuStar makes an on-board dilution and automatically corrects the final result for the dilution factor, which expands the test range to $54.3 - 1110000\mathrm{ng/mL}$ . No inhibitory prozone was detected on the highest concentrations tested.
# c. Traceability, Stability, Expected values (controls, calibrators, or methods):
The submission contained Cartridge on-board stability, Calibrator and Control on-board stability, and partial on-board Control stability (to simulate normal usage) data that supported the cartridge, control and calibrator stability claims.
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d. Detection limit:
20 replicates of House Standards Level 1 and 2 were run on an ACL AcuStar using 2 different lots of AcuStar D-Dimer reagents. Detection Limit is calculated as:
$$
\left[ S _ {1} \right] \times \frac {3 \times S D _ {0}}{R L U _ {1} - R L U _ {0}}
$$
The submission contained data to support the detection limit claim of 6.51 ng/mL
e. Analytical specificity:
The highest concentration of hemoglobin (500 mg/dL), bilirubin (18 mg/dL), triglycerides (1250 mg/dL), heparin (Low molecular Weight and Unfractionated) (2 IU/mL, rheumatoid factor (450 IU/mL), and human anti-mouse antibody (1 µg/mL) were each spiked into two samples (low and high D-Dimer concentrations) and the results compared to the unspiked sample results. To demonstrate the lack of interference of fibrinogen to the AcuStar D-Dimer assay, a positive D-Dimer sample was diluted to multiple levels with sample diluent and D-Dimer depleted plasma, and the results compared. Data demonstrated no significant interference by;
- Hemoglobin up to 500 mg/dL
- Bilirubin up to 18 mg/dL
- Triglycerides up to 1250 mg/dL
- Heparin up to 2 IU/mL
- Rheumatoid factor up to 450 IU/mL)
- Human anti-mouse antibody up to 1 µg/mL
f. Assay cut-off:
Assay cut-off was validated through ROC analysis using 150 frozen samples from non-consecutive outpatients suspected of VTE. The samples were selected to include 30% positive VTE samples and were tested with the HemosIL AcuStar D-Dimer Assay on the ACL AcuStar. A 100% Sensitivity, 35.2% Specificity, and 100% Negative Predicative Value was obtained based on a 500 ng/mL cut-off.
2. Comparison studies:
a. Method comparison with predicate device:
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In-House Study
150 frozen samples from non-consecutive outpatients suspected of VTE and 30 samples diagnosed with Disseminated Intravascular Coagulation (DIC) were tested in singlicate with HemosIL AcuStar D-Dimer on the ACL AcuStar versus the VIDAS D-Dimer Exclusion Assay. (y = 1.16 x -247, r=0.90)
Field Study #1
102 patient samples, 14 of which from patients diagnosed with VTE, were tested in singlicate with HemosIL AcuStar D-Dimer on the ACL AcuStar versus the HemosIL D-Dimer HS on an ACL TOP. Sample results ranged from 6 – 12629 ng/mL y=2.54 +383.39, r=0.89.
Field Study #2
100 patient samples, 24 of which obtained from patients diagnosed with VTE, were tested in single CATE with HemosIL AcuStar D-Dimer on the ACL AcuStar versus the BioMerieux VIDAS D-Dimer Exclusion Assay. Sample results ranged from 77 – 63131 ng/mL. y = 1.09 -51.74, r= 0.98
b. Matrix comparison:
50 fresh plasma samples were obtained from an emergency room and immediately analyzed in duplicate with the HemosIL AcuStar D-dimer reagents on an ACL AcuStar instrument and then split into two aliquots. One aliquot was stored at 2-8° C, and the other at -70° C. After one week, each aliquot was tested in duplicate, and compared to the fresh sample results. Results demonstrated good correlation ;
Fresh vs 2-8 ° C : y = 1.04 x -323, r=0.99
Fresh vs -70° C : y = 1.03x -290, r=0.99
3. Clinical studies:
344 frozen citrated plasma samples were collected from patients admitted to an emergency unit with suspected VTE. 97 were confirmed as VTE positive by standard objective tests and the remaining 247 were confirmed as negative
a. Clinical Sensitivity:
Based on the cut-off of 500 ng/mL, 100% (95% CI 96.3 to 100.0%) sensitivity and 100% (95% CI 97.3 to 100.0%) negative predictive value was obtained.
b. Clinical specificity:
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Based on the cut-off of 500 ng/mL, the study yielded a specificity of 55.5% (95% CI 49.0 to 61.8%)
c. Other clinical supportive data (when a. and b. are not applicable):
4. Clinical cut-off:
5. Expected values/Reference range:
189 citrated plasma samples obtained from healthy blood bank donors were tested in singlicate on an ACL AcuStar using one lot of HemosIL AcuStar D-Dimer reagents. 9 samples were deemed far outliers and removed from the analysis. The D-Dimer concentration distribution was not normal; therefore, non parametric statistics were applied, resulting in the following:
| Non-Parametric Limits | 95% Limit | 90% CI |
| --- | --- | --- |
| Lower | 65.5 | 53.1 -73.1 |
| Upper | 630 | 564 - 802 |
The device's package insert recommends that each laboratory establish its own normal range.
N. Instrument Name:
ACL AcuStar
O. System Descriptions:
1. Modes of Operation:
Automatic
2. Software:
FDA has reviewed applicant's Hazard Analysis and software development processes for this line of product types:
Yes ☐ X or No ☐
3. Specimen Identification:
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Barcode reader. for both the specimen and rack. If there is no sample in a rack position, the barcode reader reads the barcode on the back of the rack position that indicates an empty location.
4. Specimen Sampling and Handling:
Specimens are sampled from an open tube and automatically diluted
5. Calibration:
The assay kit contains lot dependent, bi-level lyophilized calibrators. The assay uses a 4 Parameter Logistic Curve (4PLC) fit data reduction method to generate a Master Curve which is stored in the instrument through the cartridge barcode. With the measurement of calibrators, the predefined Master Curve is transformed to a new, instrument specific 4PLC Working Curve.
6. Quality Control:
P. Other Supportive Instrument Performance Characteristics Data Not Covered In The "Performance Characteristics" Section above:
Q. Proposed Labeling:
The labeling is sufficient and it satisfies the requirements of 21 CFR Part 809.10.
R. Conclusion:
The submitted information in this premarket notification is complete and supports a substantial equivalence decision.
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Part 1 — Search, results, and everyday workflows 16 min
Part 2 — Embeddings: the galaxy map 3 min
1. Search: exact and fuzzy
Type a phrase like "coronary artery calcification" into the search box. You get two kinds of results. Exact results match the literal phrase — prefix searches work ("coronary artery calcificati") but suffix searches do not. Fuzzy results match on the meaning and intent of your phrase rather than the exact words, and are sorted by relevance score. Hover over the Exact or Fuzzy badge on any row to see exactly why it matched.
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Exact vs. fuzzy search: what's the difference?
Exact matches on the literal phrase (prefix search works, suffix does not). Fuzzy matches on the meaning and intent of the phrase rather than the exact words. Hover over the badge on any row to see why it matched.
You search "coronary artery calcification" and want only software devices with AI. What two filters do you apply?
Narrow by SaMD (software-only devices), then narrow by AI/ML (devices with AI).
2. The results table
Scroll right in the results table. The intended use is extracted for you — no need to open the PDF. The device story gives a high-level snapshot of what the device does and how it's used. The AI Performance sub-table shows each output name, acceptance criteria, observed values, and development/test dataset descriptions — the same format Innolitics uses for regulatory strategy outputs, and the fastest high-level fingerprint of an AI device. It is AI-generated but has been very reliable in practice.
Where do you find a device's intended use without opening the PDF?
Scroll right in the search results table. The intended use column is extracted for you; no need to dig into the 510(k) summary PDF.
What does the AI Performance sub-table show, and why is it useful?
Output name, acceptance criteria, observed values, development dataset description, and test dataset description. It's the same format we use for regulatory strategy output and Fast 510(k) input, and the fastest high-level fingerprint of an AI device. AI-generated but reliable in practice.
3. Judging fuzzy relevance
Fuzzy results trail off in relevance as you scroll. Use three signals to decide how far down to go: the fuzzy badge explanations, the intended use column, and whether your target output (e.g., Cobb angle) still appears in the AI Performance sub-table. Once it stops appearing, you're past the relevant zone. A top hit with a low score (~0.4) and a stretched explanation is a hint the closest predicates are far away — the project may be headed for De Novo. Note the fuzzy search is a pattern match: it doesn't handle negation ("not") well, and hardware devices can appear — filter by SaMD/AI ML to cut them.
How do you judge how far down fuzzy search results to go?
Use the relevancy signals: the fuzzy badge explanations, the intended use column, and whether the target output (e.g., Cobb angle) still appears in the AI Performance sub-table. Once it stops appearing, results are trailing off in relevancy.
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Reading rule for every project: how many summaries do you read in full?
At least the three most relevant 510(k) or De Novo summaries, in full. After that, use targeted chat questions to confirm your memory quickly. The tool supports this professional habit — it doesn't replace it.
5. Side-by-side comparison
Select multiple rows in the results table (aim for under ~10), then open the PDF Viewer tab. Ask one question — it goes to all selected devices in parallel, each with citations. This is the fastest way to compare and contrast devices: training data, PCCP scope, how they handled adding new scanners, and so on.
What does the side-by-side PDF viewer mode do?
Select multiple devices, open the PDF viewer tab, and ask one question (e.g., "Describe the training data"). It queries all selected devices simultaneously with citations, so you can compare and contrast quickly.
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With rows selected, go to the Collections tab and create a labeled collection (e.g., "Cobb Angle Project"). Reload that selection any time — before a client call, pull up the collection and ask questions across all of its devices at once.
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What can you do from the regulations tree view?
Browse product codes and regulation numbers, read the identification text and special controls, browse sibling product codes, open device PDFs on the right, and search by product code or regulation number at the top of the tree.
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Click Show Chart and segment by regulation number (or product code) to see which regulations dominate your result set. Clicking a regulation takes you into the regulations tree. Great for spotting that most matches are, say, hardware laparoscopic devices — a cue to go back and filter.
How do you see which regulations dominate a search result set?
Click "Show Chart" and segment by Regulation Number. Clicking a regulation takes you to the regulations tree.
9. The predicate graph
Open the Predicates tab for a family-tree view of predicate relationships. Click a node to trace its parents and children; selections from search carry over pre-selected. Commonly predicated devices are worth reading — a lot of people predicated them for a reason. The visual lineage is also handy on client calls, e.g. to show how a predicate family evolved and justify why your predicate still holds.
In the predicate graph, why are commonly predicated devices worth reading?
A lot of people predicated them for a reason. Clicking a node traces parents and children, and selections from search carry over pre-selected.
10. Embeddings: the galaxy map
The Embeddings tab plots every matching document in a 2-D "galaxy map" where semantically similar devices cluster together. Hover or click clusters to explore, and let AI label the clusters for you. Embeddings beat product codes for grouping: two devices can carry different product codes (LLZ vs. QIH) yet do the same thing — the embedding captures the meaning of the intended use and device story. This is also exactly how retrieval-augmented generation (RAG) works under the hood, and it makes a great visual on client calls.
Try it yourself
Head to the search page and work through a few of these AI/ML fuzzy searches to build intuition: perivascular fat on CT · aortic valve calcification opportunistic screening on noncontrast CT · breast cancer prediction on digital pathology slides · autism detection · gestational age prediction · a hearing aid that can also detect a pulse · foundation model based analysis of ECG · large language models · penetration test. Watch how the relevance scores, intended use, and AI Performance tables tell you when results stop being meaningful.