The CEDIA Digoxin II homogeneous enzyme immunoassay is for the quantitation of digoxin in human serum or plasma using automated clinical chemistry analyzers. Measurements are used in the diagnosis and treatment of digoxin overdose and in monitoring levels of digoxin to ensure proper therapy. Digoxin is widely prescribed for the treatment of congestive heart failure and various disturbances of cardiac rhythm. Therapeutic use of digoxin improves the strength of myocardial contraction and results in the beneficial effects of increased cardiac output, decreased heart size, decreased venous pressure and decreased blood volume. Digoxin therapy also results in stabilized and slowed ventricular pulse rate. Although the availability of crystalline digoxin has permitted the standardization of drug dosage, therapeutic administration inadvertently, yet frequently, results in toxicity. Importantly, symptoms of digoxin toxicity often mimic the cardiac arrhythmias for which the drug was originally prescribed. Studies suggest that up to 25% of all hospitalized patients treated with digoxin experienced some degree of toxicity, and that the mortality rate among toxic patients was more than twice that of nontoxic patients. Digoxin concentrations of 0.9 to 2.0 ng/mL in serum or plasma are normally considered to be therapeutic. Symptoms of human toxicity generally only appear at concentrations above 2.0 ng/mL; however, concentrations as low as 1.4 ng/mL may be toxic for others. Toxicity of digoxin may reflect several factors: a) The drug has a low therapeutic ratio (i.e., a very small difference exists between therapeutic and toxic tissue levels). b) Individuals vary in their response to digoxin. c) Absorption of various tablet forms of digoxin may vary over a two-fold range. d) Susceptibility to digitalis toxicity apparently increases with age. In combination with other clinical data, monitoring serum or plasma levels may provide the physician with useful information to aid in adjusting patient dosage, and achieving optimal therapeutic effect, while avoiding both subtherapeutic and harmful toxic drug levels. The CEDIA Digoxin II Assay performance has not been established with body fluids other than human serum and plasma (Na or Li heparin; Na EDTA). Digoxin-like immunoreactive substances (DLIS) have been identified in blood from patients in renal failure, liver failure, and pregnant women in the third trimester. Studies have established that the presence of DLIS in a sample can result in a false elevation of digoxin when assayed by commercially available immunoassay.
Device Story
CEDIA Digoxin II Assay is a homogeneous enzyme immunoassay for in vitro quantitative determination of digoxin in human serum/plasma. Input: patient serum/plasma sample. Principle: competitive immunoassay using genetically engineered beta-galactosidase fragments. Digoxin in sample competes with analyte-conjugated inactive enzyme fragment for antibody binding sites. If digoxin is present, antibody binds to sample analyte, allowing inactive enzyme fragments to reassociate into active enzyme; active enzyme cleaves substrate, producing color change measured spectrophotometrically at 570 nm. Output: quantitative digoxin concentration (ng/mL). Used in clinical laboratories on automated chemistry analyzers (e.g., Hitachi 911). Results interpreted by physicians to adjust dosage, ensure therapeutic efficacy, and avoid toxicity. Benefits: aids in managing narrow therapeutic index of digoxin, reducing risk of toxicity-related mortality.
Clinical Evidence
Bench testing only. Precision studies (N=120 per level) showed within-run %CV of 1.56-4.25% and total %CV of 2.34-5.44%. Method comparison against Abbott TDx (N=99) yielded correlation r=0.955 (Least Squares y=0.98x-0.12; Deming y=1.02x-0.17). Linearity established from 0.15-4 ng/mL. Interference testing performed for bilirubin, hemoglobin, triglycerides, lipemia, and total protein. Specificity evaluated via cross-reactivity testing against various digoxin metabolites and related compounds.
Technological Characteristics
Homogeneous enzyme immunoassay using genetically engineered beta-galactosidase fragments. Detection: spectrophotometric at 570 nm. Sample types: human serum and plasma (Na/Li heparin, Na EDTA). Assay range: 0.15-4 ng/mL. Instrument: Hitachi 911 automated clinical chemistry analyzer.
Indications for Use
Indicated for quantitative determination of digoxin in human serum or plasma for patients undergoing digoxin therapy for congestive heart failure or cardiac rhythm disturbances. Used to monitor therapeutic levels, diagnose overdose, and adjust dosage. Contraindicated for use with body fluids other than serum or plasma; caution advised for patients with renal failure, liver failure, or third-trimester pregnancy due to potential for false elevations from Digoxin-like immunoreactive substances (DLIS).
Regulatory Classification
Identification
A digoxin test system is a device intended to measure digoxin, a cardiovascular drug, in serum and plasma. Measurements obtained by this device are used in the diagnosis and treatment of digoxin overdose and in monitoring levels of digoxin to ensure appropriate therapy.
{0}
K970883
MAY 21, 1997
# 510(k) Summary
## BOEHRINGER MANNHEIM CORPORATION
### Introduction
According to the requirements of 21 CFR 807.92, the following information provides sufficient detail to understand the basis for a determination of substantial equivalence.
---
### 1. Submitter name, address, contact
Boehringer Mannheim Corporation
2400 Bisso Lane
P.O. Box 4117
Concord, CA 94524-4117
(510) 674 - 0690, extension 8240
Fax: (510) 687-1850
Contact Person: Yvette Lloyd
Date Prepared: March 6, 1997
---
### 2. Device name
Proprietary name: CEDIA® Digoxin II Assay
Common name: Homogeneous enzyme immunoassay for the determination of Digoxin.
Classification name: Enzyme immunoassay, Digoxin
---
### 3. Predicate device
The Boehringer Mannheim CEDIA® Digoxin II is substantially equivalent to other products in commercial distribution intended for similar use. Most notably it is substantially equivalent to the currently marketed Abbott TDx® Digoxin II Assay (K882233).
---
Continued on next page
page 28
{1}
510(k) Summary, Continued
BOEHRINGER MANNHEIM CORPORATION
4. Device Description
The CEDIA® Digoxin II Assay is based on the bacterial enzyme β-galactosidase, which has been genetically engineered into two inactive fragments. These fragments spontaneously reassociate to form fully active enzyme that, in the assay format, cleaves a substrate, generating a color change that can be measured spectrophotometrically.
In the assay, digoxin in the sample competes with analyte conjugated to one inactive fragment of β-galactosidase for antibody binding site. If analyte is present in the sample, it binds to antibody, leaving the inactive enzyme fragments free to form active enzyme. If analyte is not present in the sample, antibody binds to analyte conjugated on the inactive fragment, inhibiting the reassociation of inactive β-galactosidase fragments, and no active enzyme is formed.
Continued on next page
page 29
{2}
510(k) Summary, Continued
## BOEHRINGER MANNHEIM CORPORATION
5. Intended use
Immunoassay for the in vitro quantitative determination of Digoxin in human serum and plasma.
6. Comparison to predicate device
The Boehringer Mannheim CEDIA® Digoxin II Assay is substantially equivalent to other products in commercial distribution intended for similar use. Most notably it is substantially equivalent to the currently marketed Abbott TDx® Digoxin II Assay (K882233).
The following table compares the CEDIA® Digoxin II Assay with the predicate device, Abbott TDx® Digoxin II Assay. Specific data on the performance of the test have been incorporated into the draft labeling in attachment 5. Labeling for the predicate device is provided in attachment 6.
### Similarities:
- Intended Use: Immunoassay for the in vitro quantitative determination of Digoxin
- Sample type: Serum and plasma
- Assay range: 0.15 - 4 ng/mL
Continued on next page
{3}
510(k) Summary, Continued
BOEHRINGER MANNHEIM CORPORATION
6. Comparison to predicate device cont.
## Differences:
| Feature | CEDIA® Digoxin II | TDx Digoxin II |
| --- | --- | --- |
| Reaction test principle | Spectrophotometric 570 nm | Fluorescence Polarization |
| Instrument required | Hitachi 911 | Abbott TDx |
## Performance Characteristics:
| Feature | CEDIA® Digoxin II | | | TDx Digoxin II | | |
| --- | --- | --- | --- | --- | --- | --- |
| Precision | Modified NCCLS (ng/mL): | | | NCCLS (ng/mL): | | |
| Level | Level 1 | Level 2 | Level 3 | Low | Mid | High |
| N | 120 | 120 | 120 | 50 | 50 | 50 |
| Within run | 1.1 | 1.8 | 3.8 | 0.70 | 1.44 | 3.66 |
| %CV | 4.25 | 2.22 | 1.56 | 5.75 | 3.15 | 1.87 |
| Total | 1.1 | 1.8 | 3.8 | 0.70 | 1.44 | 3.66 |
| %CV | 5.44 | 3.58 | 2.34 | 7.67 | 3.98 | 1.91 |
Continued on next page
21
page 31
{4}
510(k) Summary, Continued
BOEHRINGER
MANNHEIM
CORPORATION
6. Comparison to predicate device, (cont.)
Performance Characteristics:
| Feature | CEDIA® Digoxin II | TDx Digoxin II |
| --- | --- | --- |
| Lower Detection Limit | 0.15 ng/mL | 0.2 ng/mL |
| Linearity | 0.15 - 4 ng/mL | 0.0 - 4.0 ng/mL |
| Method Comparison | Vs Abbott TDx Digoxin | Vs Baxter Dade Stratus |
| | Least Squares
y =0.98x - 0.12
r=0.955
N=99 | y =0.94x + 0.08
r=0.962
N=200 |
| | Deming's:
y=1.02x - 0.17
r=0.955
N=99 | |
Continued on next page
page 32
{5}
510(k) Summary, Continued
BOEHRINGER MANNHEIM CORPORATION
6. Comparison to predicate device, (cont.)
Performance Characteristics:
p.58
p.61
| Feature | CEDIA® Digoxin II | TDx Digoxin II |
| --- | --- | --- |
| Interfering substances | No interference at: (within ±10% of baseline)
1€ | No interference at: |
| Bilirubin | 66 mg/dL | 20 mg/dL |
| Hemoglobin | 1000 mg/dL | 1000 mg/dL |
| Triglyceride | 100 mg/dL | 2500 mg/dL |
| Lipemia | 10 g/dL | N/A |
| Total Protein | 100 IU/mL | N/A |
| Rheumatoid Factor | | |
| Specificity | % Cross-reactivity | % Cross-reactivity |
| Digoxigenin | 60.5 | up to 200 |
| β-Acetyldigoxin | 77.0 | not tested |
| α-Acetyldigoxin | 75.3 | not tested |
| Gitalin | 2.1 | not tested |
| Digoxigenin-Mono-Digitoxiside | 102.5 | up to 200 |
| Digitoxin-Bis-Digitoxiside | 86.3 | up to 200 |
| Digitoxin | 1.5 | 4.8 |
| β-Methyldigoxin | 76.3 | not tested |
| 3-Epe-Digoxigenin | 37.6 | not tested |
| Dehydrodigoxigenin | 82.6 | not tested |
| Epi-Digoxigenin-Glucuronide | 42.9 | not tested |
page 33
{6}
DEPARTMENT OF HEALTH & HUMAN SERVICES
Public Health Service
Food and Drug Administration
2098 Gaither Road
Rockville MD 20850
MAY 21 1997
Yvette R. Lloyd
Regulatory Affairs Specialist
Boehringer Mannheim Corporation
2400 Bisso Lane
P.O. Box 4117
Concord, California 94524-4117
Re: K970883
CEDIA® Digoxin II Assay
Regulatory Class: II
Product Code: KXT
Dated: April 18, 1997
Received: April 24, 1997
Dear Ms. Lloyd:
We have reviewed your Section 510(k) notification of intent to market the device referenced above and we have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to 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). 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.
If your device is classified (see above) into either class II (Special Controls) or class III (Premarket Approval), it may be subject to such additional controls. Existing major regulations affecting your device can be found in the Code of Federal Regulations, Title 21, Parts 800 to 895. A substantially equivalent determination assumes compliance with the Good Manufacturing Practice for Medical Devices: General (GMP) regulation (21 CFR Part 820) and that, through periodic GMP inspections, the Food and Drug Administration (FDA) will verify such assumptions. Failure to comply with the GMP regulation may result in regulatory action. In addition, FDA may publish further announcements concerning your device in the Federal Register. Please note: this response to your premarket notification submission does not affect any obligation you might have under sections 531 through 542 of the Act for devices under the Electronic Product Radiation Control provisions, or other Federal laws or regulations.
{7}
Page 2
Under the Clinical Laboratory Improvement Amendments of 1988 (CLIA-88), this device may require a CLIA complexity categorization. To determine if it does, you should contact the Centers for Disease Control and Prevention (CDC) at (770) 488-7655.
This letter will allow you to begin marketing your device as described in your 510(k) premarket notification. The FDA finding of substantial equivalence of your device to a legally marketed predicate device results in a classification for your device and thus, permits your device to proceed to the market.
If you desire specific advice for your device on our labeling regulation (21 CFR Part 801 and additionally 809.10 for in vitro diagnostic devices), please contact the Office of Compliance at (301) 594-4588. Additionally, for questions on the promotion and advertising of your device, please contact the Office of Compliance at (301) 594-4639. Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR 807.97). Other general information on your responsibilities under the Act may be obtained from the Division of Small Manufacturers Assistance at its toll-free number (800) 638-2041 or (301) 443-6597 or at its internet address "http://www.fda.gov/cdrh/dsmamain.html".
Sincerely yours,
Steven I. Gutman
Steven I. Gutman, M.D., M.B.A.
Director
Division of Clinical Laboratory Devices
Office of Device Evaluation
Center for Devices and Radiological Health
Enclosure
2
{8}
510(k) Number (if known): N/A
K910883
Device Name: CEDIA® Digoxin II Assay
Indications For Use:
The CEDIA Digoxin II homogeneous enzyme immunoassay is for the quantitation of digoxin in human serum or plasma using automated clinical chemistry analyzers. Measurements are used in the diagnosis and treatment of digoxin overdose and in monitoring levels of digoxin to ensure proper therapy.
Digoxin is widely prescribed for the treatment of congestive heart failure and various disturbances of cardiac rhythm. Therapeutic use of digoxin improves the strength of myocardial contraction and results in the beneficial effects of increased cardiac output, decreased heart size, decreased venous pressure and decreased blood volume. Digoxin therapy also results in stabilized and slowed ventricular pulse rate.
Although the availability of crystalline digoxin has permitted the standardization of drug dosage, therapeutic administration inadvertently, yet frequently, results in toxicity. Importantly, symptoms of digoxin toxicity often mimic the cardiac arrhythmias for which the drug was originally prescribed. Studies suggest that up to 25% of all hospitalized patients treated with digoxin experienced some degree of toxicity, and that the mortality rate among toxic patients was more than twice that of nontoxic patients. Digoxin concentrations of 0.9 to 2.0 ng/mL in serum or plasma are normally considered to be therapeutic. Symptoms of human toxicity generally only appear at concentrations above 2.0 ng/mL; however, concentrations as low as 1.4 ng/mL may be toxic for others.
Concurrence of CDRH, Office of Device Evaluation (ODE)
Prescription Use ☑ (Per 21 CFR 801.109)
OR
Over-The-Counter Use ☐ (Optional Format 1-2-96)

75
{9}
INDICATIONS FOR USE, Continued:
Toxicity of digoxin may reflect several factors: a) The drug has a low therapeutic ratio (i.e., a very small difference exists between therapeutic and toxic tissue levels). b) Individuals vary in their response to digoxin. c) Absorption of various tablet forms of digoxin may vary over a two-fold range. d) Susceptibility to digitalis toxicity apparently increases with age.
In combination with other clinical data, monitoring serum or plasma levels may provide the physician with useful information to aid in adjusting patient dosage, and achieving optimal therapeutic effect, while avoiding both subtherapeutic and harmful toxic drug levels.
The CEDIA Digoxin II Assay performance has not been established with body fluids other than human serum and plasma (Na or Li heparin; Na EDTA). Digoxin-like immunoreactive substances (DLIS) have been identified in blood from patients in renal failure, liver failure, and pregnant women in the third trimester. Studies have established that the presence of DLIS in a sample can result in a false elevation of digoxin when assayed by commercially available immunoassay.
Concurrence of CDRH, Office of Device Evaluation (ODE)
Prescription Use (Per 21 CFR 801.109)
OR
Over-The-Counter Use
(Optional Format 1-2-96)
page 26
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Two short videos show you everything — or skip straight to the written tutorial if you'd rather read. You can reopen this any time from the Tutorial button in the top bar.
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.
Use the checkboxes above the results to narrow: SaMD keeps only software-only devices, AI / ML keeps only devices with AI.
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.
4. Device detail page: chat and citations
Click a device name to open its detail page: device facts on the left, a chat window on the right. Ask something like "Describe the training data". The answer carries little citation bubbles — click one to jump to the highlighted passage in the source PDF, so you can verify every AI answer against the document. There's also a Download PDF button for sharing.
How do you verify an AI chat answer on the device detail page?
Click the citation bubbles to jump to the relevant highlight in the source document.
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.
6. Collections
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.
How do you save a set of selected devices for later use?
Select the rows, go to the Collections tab, and create a labeled collection (e.g., "Cobb Angle Project"). You can reload the selection anytime and carry it into the PDF viewer and other tabs that support selections.
7. Product codes and the regulations tree
Click a product code in the results to jump to it in the regulations tree — identification text, sibling product codes, and devices you can open in a PDF viewer on the right. Click a regulation number to see its identification, special controls, and related product codes. You can also search by product code or regulation number at the top of the tree. Always read the special controls if any exist for your device — it broadens your search and sharpens pre-kickoff research.
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.
8. Chart view
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.