K040407 · Immunetics, Inc. · NRL · Jun 3, 2004 · Microbiology
Device Facts
Record ID
K040407
Device Name
QUICKELISA ANTHRAX-PA KIT
Applicant
Immunetics, Inc.
Product Code
NRL · Microbiology
Decision Date
Jun 3, 2004
Decision
SESE
Submission Type
Traditional
Regulation
21 CFR 866.3045
Device Class
Class 2
Indications for Use
The Immunetics® QuickELISA™ Anthrax-PA Kit is intended for use in the qualitative detection of antibodies to the Protective Antigen (PA) protein of B. anthracis in human serum. The assay should be used only on serum samples from individuals with a clinical history, signs or symptoms consistent with anthrax infection as an aid in the diagnosis of anthrax, or from recipients of anthrax vaccine.
Device Story
The QuickELISA Anthrax-PA Kit is an in vitro diagnostic ELISA for detecting total antibodies (IgG/IgM) against B. anthracis Protective Antigen (PA) in human serum. The assay uses a single-step binding process where serum antibodies form ternary complexes with biotinylated streptavidin-rPA and rPA-horseradish peroxidase (HRP) conjugates. These complexes bind to a biotin-coated microplate. After washing, a chromogenic TMB substrate is added; the resulting color change is measured via optical absorbance at 450nm (with 620-650nm background subtraction) using an ELISA microplate reader. The test is performed in a laboratory setting by trained personnel. Results are qualitative (or semi-quantitative with serial dilutions) and serve as an aid in diagnosis alongside clinical history and other laboratory data. The device benefits patients by providing rapid presumptive detection of anthrax-specific antibodies, supporting clinical decision-making for infection management or vaccine response assessment.
Clinical Evidence
Performance evaluated using serum panels. Specificity: 99.14% (n=578) in normal human sera. Cross-reactivity: 99.56% (n=225) across various disease conditions (e.g., HIV, SLE, Influenza, H. pylori). Sensitivity: 100% in AVA vaccinees (n=49), cutaneous anthrax patients (n=18), and inhalational anthrax patients (n=16). Analytical sensitivity established at ≤31.3 ng/mL. Reproducibility demonstrated across intra-assay, inter-assay, and inter-lot studies.
Technological Characteristics
Microwell ELISA format; utilizes biotin-coated microplate, streptavidin-rPA, and rPA-HRP conjugates. Detection via chromogenic TMB substrate and optical absorbance measurement at 450nm. Requires ELISA microplate reader. No specific materials standards cited. Standalone diagnostic kit.
Indications for Use
Indicated for qualitative detection of IgG and IgM antibodies to B. anthracis Protective Antigen (PA) in human serum. Patient population includes individuals with clinical history, signs, or symptoms consistent with anthrax infection, anthrax vaccine recipients, or those with presumed contact with anthrax spores/bacilli. Not evaluated for asymptomatic individuals with suspected exposure; results for gastrointestinal anthrax unknown.
Regulatory Classification
Identification
An in vitro diagnostic device for Bacillus species (spp.) detection is a prescription device used to detect and differentiate among Bacillus spp. and presumptively identify B. anthracis and other Bacillus spp. from cultured isolates or clinical specimens as an aid in the diagnosis of anthrax and other diseases caused by Bacillus spp. This device may consist of Bacillus spp. antisera conjugated with a fluorescent dye (immunofluorescent reagents) used to presumptively identify bacillus-like organisms in clinical specimens; bacteriophage used for differentiating B. anthracis from other Bacillus spp. based on susceptibility to lysis by the phage; or antigens used to identify antibodies to B. anthracis (anti-toxin and anti-capsular) in serum. Bacillus infections include anthrax (cutaneous, inhalational, or gastrointestinal) caused by B. anthracis, and gastrointestinal disease and non-gastrointestinal infections caused by B. cereus.
Special Controls
*Classification.* Class II (special controls). The special controls are set forth in FDA's special controls guideline document entitled “In Vitro Diagnostic Devices for*Bacillus* spp. Detection; Class II Special Controls Guideline for Industry and Food and Drug Administration Staff.” For availability of the guideline document, see § 866.1(e).(c)
*Restriction on Distribution.* The distribution of these devices is limited to laboratories that follow public health guidelines that address appropriate biosafety conditions, interpretation of test results, and coordination of findings with public health authorities.(d)
*Restriction on Use.* The use of this device is restricted to prescription use and must comply with the following:(1) The device must be in the possession of:
(i)(A) A person, or his agents or employees, regularly and lawfully engaged in the manufacture, transportation, storage, or wholesale or retail distribution of such device; or
(B) A practitioner, such as a physician, licensed by law to use or order the use of such device; and
(ii) The device must be sold only to or on the prescription or other order of such practitioner for use in the course of his professional practice.
(2) The label of the device shall bear the statement “Caution: Federal law restricts this device to sale by or on the order of a ____”, the blank to be filled with the word “physician” or with the descriptive designation of any other practitioner licensed by the law of the State in which he practices to use or order the use of the device.
(3) Any labeling, as defined in section 201(m) of the Federal Food, Drug, and Cosmetic Act, whether or not it is on or within a package from which the device is to be dispensed, distributed by, or on behalf of the manufacturer, packer, or distributor of the device, that furnishes or purports to furnish information for use of the device contains adequate information for such use, including indications, effects, routes, methods, and frequency and duration of administration and any relevant hazards, contraindications, side effects, and precautions, under which practitioners licensed by law to employ the device can use the device safely and for the purposes for which it is intended, including all purposes for which it is advertised or represented. This information will not be required on so-called reminder-piece labeling which calls attention to the name of the device but does not include indications or other use information.
(4) All labeling, except labels and cartons, bearing information for use of the device also bears the date of the issuance or the date of the latest revision of such labeling.
Predicate Devices
US Army Biological Laboratories reagents for modified agar diffusion assay
Submission Summary (Full Text)
{0}
1
# 510(k) SUBMISSION TEMPLATE
A. 510(k) Number: K040407
B. Analyte: Antibodies to Protective Antigen (PA) protein, *Bacillus anthracis*
C. Type of Test: ELISA
D. Applicant: Immunetics, Inc.
E. Proprietary and Established Names of the Product: QuickELISA™ Anthrax-PA Kit
F. Regulatory Information:
1. Regulation section: Unclassified
2. Classification: Unclassified
3. Product code: NRL - ENZYME LINKED IMMUNOABSORBENT ASSAY, ANTIBODY, B. ANTHRACIS
4. Panel: 83
G. Intended Use and Indication for Use:
1. Intended use(s): The Immunetics® QuickELISA™ Anthrax-PA Kit is intended for use in the qualitative detection of antibodies to the Protective Antigen (PA) protein of *B. anthracis* in human serum. The assay should be used only on serum samples from individuals with a clinical history, signs or symptoms consistent with anthrax infection as an aid in the diagnosis of anthrax, or from recipients of anthrax vaccine.
2. Indication(s) for use: The assay should be used only on serum samples from individuals with a clinical history, signs or symptoms consistent with anthrax infection as an aid in the diagnosis of anthrax, or from recipients of anthrax vaccine.
3. Special conditions for use statement(s):
- The diagnosis of anthrax infection must be made based on history, signs, symptoms, exposure likelihood, and when possible other laboratory data, in addition to the presence of antibodies to *B. anthracis* PA. Negative results in ELISA should not be used in isolation from other evidence to exclude anthrax.
- The assay has not been evaluated in individuals without clinical signs or symptoms who were presumed exposed and who subsequently developed cutaneous or inhalation anthrax. There is no information available to interpret the meaning of a positive or negative test result for such individuals.
- The assay has not been evaluated with specimens from patients infected by the gastrointestinal route; expected results with such infections are unknown.
- The minimum level of anti-PA antibodies that confers protection following vaccination is not known. The QuickELISA measures total antibody and the
{1}
relationship between this value and protective immunity has not been established.
- The affinity and/or avidity of anti-PA IgG and IgM for the rPA antigen have not been determined with this assay.
This assay is for Rx use.
4. Special instrument requirements: ELISA reader, dual wavelength; ELISA plate washer; microplate shaker
## H. Device Description:
The QuickELISA assay kit includes necessary reagents to perform laboratory testing, using immunochemical reactions in an ELISA plate format. Conjugates are manufactured from a recombinant protein product produced by an avirulent plasmidless B. anthracis strain. Kit reagents include positive controls (sera from rabbits immunized with recombinant PA), Conjugate A (streptavidin-rPA), Conjugate B (rPA-horseradish peroxidase), a negative control (normal human serum), microwell strips (precoated with biotinylated bovine serum albumin, sample diluent, TMB substrate, wash buffer, and stop reagent. An ELISA reader (dual wavelength), ELISA plate washer and microplate shaker are needed to perform the testing. The cutoff was determined based on preclinical testing to be above the highest negative sample and validated to detect approximately 300 ng/mL of PA-specific antibody (pool of vaccinee sera).
## I. Substantial Equivalence Information (if known):
1. Predicate device name(s): preamendments device, US Army Biological Laboratories reagents for modified agar diffusion assay
2. Predicate 510(k) number(s): NA
3. Comparison with predicate:
| Similarities | | |
| --- | --- | --- |
| Item | Device | Predicate |
| Intended Use | Detection of anti-PA antibodies | Same |
| Specimen Type | Serum | Same |
| Negative Control | Normal human serum | Same |
| Differences | | |
| Item | Device | Predicate |
| Antigen | Recombinant PA (Protective Antigen) | Purified PA from Sterne strain culture |
| Assay Endpoint | Spectrophotometric measure (Net OD-450) | Visualized band of identity |
| Positive Control | Pooled sera from rabbits immunized with rPA | Serum dilution from human vaccinee |
| Testing Time | Overnight (18-24 h) | 35 min (with agitation); 80 min (without agitation) |
| | | |
{2}
J. Standard/Guidance Document Referenced (if applicable): NA
K. Test Principle: Immunochemical using ELISA microwell plate format.
L. Performance Characteristics:
1. Analytical performance:
a. Precision(Repeatability/Reproducibility):
| Reproducibility Panel Sample | Agitated Incubations: Intra-Assay | | Agitated Inter-Assay CV % | Agitated Inter-Lot CV % | Agitated Inter-Site CV % | Stationary Intra-Assay CV % | Stationary vs. Agitated CV % |
| --- | --- | --- | --- | --- | --- | --- | --- |
| | Net OD-450 | CV % | | | | | |
| PC | 2.233 | 4.4 | 2.0 | 11.2 | 35.4 | 10.8 | 15.1 |
| Low PC | 0.860 | 4.1 | 1.5 | 10.2 | 13.8 | 13.2 | 11.6 |
| NC | 0.018 | 7.2 | 6.2 | 5.4 | 18.1 | 10.8 | 27.9 |
| HiP1 | 3.809 | 6.2 | 0.4 | 2.2 | 3.9 | 6.6 | 1.3 |
| HiP2 | 3.830 | 5.6 | 0.5 | 0.9 | 3.5 | 7.6 | 1.2 |
| HiP3 | 3.806 | 5.2 | 2.0 | 1.7 | 1.9 | 6.9 | 0.8 |
| LoP1 | 2.225 | 6.1 | 2.5 | 22.6 | 15.3 | 3.2 | 19.0 |
| LoP2 | 0.609 | 7.9 | 3.0 | 26.3 | 4.0 | 4.5 | 27.1 |
| LoP3 | 0.442 | 8.3 | 6.4 | 20.5 | 10.0 | 7.9 | 22.9 |
| N1 | 0.019 | 9.5 | 21.5 | 19.2 | 7.9 | 10.9 | 12.8 |
| N2 | 0.021 | 8.0 | 23.1 | 14.9 | 23.9 | 9.9 | 12.8 |
| N3 | 0.021 | 5.9 | 9.5 | 18.5 | 19.8 | 3.0 | 37.3 |
| N4 | 0.021 | 12.2 | 6.4 | 13.6 | 20.9 | 2.3 | 33.5 |
| N5 | 0.023 | 14.3 | 8.6 | 24.2 | 20.2 | 6.1 | 32.4 |
| REF-1 | 0.357 | 8.6 | 8.4 | 15.7 | 13.7 | 7.6 | 15.4 |
| MeP1 | 2.575 | 6.7 | 7.8 | 16.0 | 15.9 | 5.0 | 5.2 |
b. Linearity/Assay measuring (reportable) range: NA
c. Calibrators, and Controls: Pooled sera from rabbits immunized with rPA
d. Traceability of the assay: NA
e. Analytical limits at low levels: approx. 300 ng of PA-specific antibody
f. Analytical specificity:
Sera from 225 individuals with other antibody responses associated with various disease conditions, and 583 sera from healthy blood donors were tested with QuickELISA. Positive results were obtained for 5/583 (0.9%) blood donors and 1/225 (0.4%) of patients with other disease conditions.
g. Analytical characterization of cut-off:
Titrations of pooled human sera from AVA vaccinees (standardized using radial immunodiffusion and nephelometry with US National Reference Preparation for Specific Human Serum Proteins, and mass value using USFDA reference serum, 1983 H. influenzae type b)
2. Comparison studies using clinical specimens:
a. Method comparison: NA
b. Matrix description and comparison: NA
3. Clinical Studies :
a. Clinical sensitivity and clinical specificity: NA – anthrax infection would not be expected in a US population.
{3}
b. Other clinical supportive data, statistical analysis and results if applicable: Archived sera from patients diagnosed with inhalational or cutaneous anthrax (n=13 US patients and 6 non-US patients), along with 49 AVA vaccine recipients were tested with QuickELISA. The anthrax sera were collected 17 days to 15 months post-infection and after development of symptoms. All sera from patients with anthrax were positive when tested with the QuickELISA.
4. Clinical cut-off: The cutoff is determined by adding 0.1 to the average of duplicate Negative Control Net OD-450. This level was determined to be higher than readings obtained from sera from unvaccinated/uninfected individuals in preclinical testing.
5. Reference interval (Expected values): Anthrax is virtually non-existent in the US. All AVA-vaccinated individuals that have been evaluated are reported to develop an anti-PA immune response. The magnitude of the Net OD-450 measurement is not correlated with antibody level or an endpoint titer.
N. Conclusion: The submitted information in this premarket notification is complete and supports a substantial equivalence decision.
4
Predicate graph will load when search results are available.
Embedding visualization will load when search results are available.
PDF viewer will load when search results are available.
Loading panels...
Select an item from Submissions
Click any panel, subpart, regulation, product code, or device to see details here.
Section Matches
Results will appear here.
Product Code Matches
Results will appear here.
Special Control Matches
Results will appear here.
Loading collections...
Loading
My Alerts
You will receive email notifications based on the filters and frequency you set for each alert.
Sort by:
Create Alert
Search Filters
Agent Token
Create a read-only bearer token for Claude, ChatGPT, or other agents that can call HTTP APIs.
Copy this now. It will not be shown again.
Connected apps
Apps you authorized through browser sign-in. Disconnecting revokes their access immediately.
Learn the FDA Browser
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.
