FebriDx Bacterial/Non-bacterial Assay

K260787 · Lumos Diagnostics, Inc. · QXA · Mar 24, 2026 · Microbiology

Device Facts

• Record ID: K260787
• Device Name: FebriDx Bacterial/Non-bacterial Assay
• Applicant: Lumos Diagnostics, Inc.
• Product Code: QXA · Microbiology
• Decision Date: Mar 24, 2026
• Decision: SESE
• Submission Type: Dual Track
• Regulation: 21 CFR 866.3230
• Device Class: Class 2

Indications for Use

The FebriDx Bacterial/Non-bacterial Assay is a qualitative visually read rapid immunoassay for the detection of human host response proteins, Myxovirus resistance protein A (MxA) and C-reactive protein (CRP) directly from fingerstick blood. FebriDx is indicated for use in patients aged 12-64 for evaluation of acute respiratory infection who have had symptoms for less than 7 days and within 3 days of fever onset. FebriDx test results are intended to be used in conjunction with other clinical and diagnostic findings as an aid in the diagnosis of bacterial acute respiratory infection and differentiation from non-bacterial etiology. The assessment of whether a bacterial infection is present should always be based on consideration of all available information, and not based solely on the FebridDx test results. FebriDx test results are not intended to identify a specific pathogen or the severity of infection. FebriDx External Controls: FebriDx External Controls are used in the FebriDx Test as assayed quality control samples to assess the performance and reliability of the FebriDx Test. Special conditions for use statement(s): • For in vitro diagnostic use • For prescription use only

Device Story

Single-use, disposable lateral flow immunoassay; detects host response proteins MxA and CRP in fingerstick blood. Integrated platform includes retractable safety lancet, blood collection/transfer tube, and buffer delivery system. Operator adds blood and buffer; sample migrates through membrane with immobilized capture antibodies. Visual result: black line indicates bacterial infection; red line or no line indicates non-bacterial etiology. Used in point-of-care settings by professionals. Results aid clinical decision-making for respiratory infections; intended to be used with other clinical findings. Benefits include rapid differentiation of infection etiology to guide management.

Clinical Evidence

Prospective, multi-center, blinded clinical trial (DISRUPT study) with 520 symptomatic ARI participants. Compared to a composite Clinical Reference Algorithm (pathogen detection + host immune response + expert adjudication). Overall PPA 93.2% (95% CI 84.9-97.0%), NPA 88.4% (95% CI 85.0-91.1%). Microbiologically confirmed subgroup: PPA 100%, NPA 91.0%. No significant performance differences across age groups.

Technological Characteristics

Lateral flow immunochromatographic assay. Detects MxA (~40 ng/mL) and CRP (~20 mg/L). Components: nitrocellulose membrane, latex beads conjugated to antibodies, leukocyte membrane lysing agents. Single-use disposable cassette. Storage 4-25°C. 24-month shelf life. Visual read.

Indications for Use

Indicated for patients aged 12-64 presenting with acute respiratory infection symptoms <7 days and fever onset within 3 days. Used as an aid to differentiate bacterial from non-bacterial etiology.

Regulatory Classification

Identification

A device to detect and measure non-microbial analytes to aid in the detection and identification of localized human infections is identified as an in vitro diagnostic device intended for the detection and qualitative measurement, quantitative measurement, or both of one or more non-microbial analytes in human clinical specimens to aid in the assessment, identification, or both of a localized microbial infection when used in conjunction with clinical signs and symptoms and other clinical and laboratory findings.

Special Controls

The special controls for this device are:

*Classification.* Class II (special controls). The special controls for this device are:(1) Any sample collection device used must be FDA-cleared, -approved, or -classified as 510(k) exempt (standalone or as part of a test system) for the collection of human specimens; alternatively, the sample collection device must be cleared in a premarket submission as a part of this device. (2) The labeling required under § 809.10(b) of this chapter must include: (i) An intended use with a detailed description of what the device detects and measures, the type of results provided to the user, the sample type, whether the measure is qualitative and/or quantitative, the clinical indications for the test use, and the specific population(s) for which the device is intended. (ii) A detailed description of the performance characteristics of the device for all intended specimen types from the analytical and clinical studies (as applicable) required under paragraphs (b)(3)(ii) and (iii) of this section. (iii) A detailed explanation of the interpretation of results, including acceptance criteria for evaluating the validity of individual runs ( *e.g.,* assessment of internal and/or external quality controls, as applicable).(iv) The following limiting statements: (A) A statement that a negative test result does not preclude the possibility of infection; (B) A statement that the test results should be interpreted in conjunction with other clinical and laboratory data available to the clinician; (C) A statement that consistent device performance is dependent on adequate specimen collection, transport, storage, and processing. Failure to observe proper procedures in any one of these steps can lead to incorrect results; and (D) A statement that details any limitations associated with the samples, as appropriate ( *e.g.,* collected on the day of admission to the intensive care unit).(3) Design verification and validation must include the following: (i) A detailed device description, including as appropriate, all device parts; control elements incorporated into the test procedure; instrument requirements; reagents required but not provided; and the principle of device operation and test methodology, including all preanalytical methods for the processing of specimens and the methodology from obtaining a sample to the result; design of primer/probe sequences; rationale for target analyte selection; and computational path from collected raw data to reported result ( *e.g.,* how collected raw signals are converted into a reported result).(ii) Detailed documentation of analytical studies including analytical sensitivity (Limit of Detection, Limit of Quantitation, and Limit of Blank), inclusivity, cross-reactivity, microbial interference, interfering substances, competitive inhibition, carryover/cross-contamination, specimen stability, within-lab precision, reproducibility, and linearity, as applicable. (iii) Detailed documentation and results either from a clinical study, that includes prospective (sequentially collected) samples for each intended specimen type that are representative of the intended use populations and, when determined to be acceptable by FDA, additional characterized clinical samples; or, when determined to be acceptable by FDA, an equivalent sample set. The clinical study must compare the device performance to results obtained from an FDA-accepted reference method and/or FDA-accepted comparator method, as appropriate. Documentation from the clinical studies must include the clinical study protocol ( *e.g.,* the predefined statistical analysis plan), clinical study report, testing results, and results of all statistical analyses.(iv) An evaluation of the level of the non-microbial analyte in asymptomatic patients with demographic characteristics ( *e.g.,* age, racial, ethnic, and sex distribution) similar to the intended use population of the device.(v) Documentation of an appropriate end user device training program that will be offered as part of efforts to mitigate the risks of false results, failure to operate the device correctly, and failure to interpret test results correctly. (vi) An appropriate risk mitigation strategy to ensure that the device does not prevent any other device(s) with which it is indicated for use, including incorporated device(s), from achieving their intended use ( *e.g.,* safety and effectiveness of the functions of the indicated device(s) remain unaffected).(vii) A detailed description of the impact of any software, including software applications and hardware-based devices that incorporate software, on the device's functions.

Predicate Devices

• FebriDx Bacterial / Non-bacterial Point-of-Care Assay (K230917)

Submission Summary (Full Text)

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FDA

U.S. FOOD &amp; DRUG

ADMINISTRATION

# 510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION DECISION SUMMARY

ASSAY ONLY

## I Background Information:

A 510(k) Number

K260787

B Applicant

Lumos Diagnostics, Inc.

C Proprietary and Established Names

FebriDx Bacterial / Non-Bacterial Assay

D Regulatory Information

| Product Code(s) | Classification | Regulation Section | Panel |
| --- | --- | --- | --- |
| QXA | Class II | 21 CFR 866.3230 - Device To Detect And Measure Non-Microbial Analytes To Aid In The Detection And Identification Of Localized Human Infections | MI - Microbiology |

## II Submission/Device Overview:

A Purpose for Submission:

A Dual Submission to obtain a substantial equivalence determination for that the FebriDx Bacterial / Non-Bacterial Assay (FebriDx test).

B Measurand:

Myxovirus resistance protein A (MxA) and C-reactive protein (CRP)

C Type of Test:

Lateral flow immunochromatography

Food and Drug Administration

10903 New Hampshire Avenue

Silver Spring, MD 20993-0002

www.fda.gov

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III Intended Use/Indications for Use:

A Intended Use(s):
See Indications for Use below.

B Indication(s) for Use:
The FebriDx Bacterial/Non-Bacterial Assay is a qualitative visually read rapid immunoassay for the detection of human host response proteins, Myxovirus resistance protein A (MxA) and C-reactive protein (CRP) directly from fingerstick blood. FebriDx is indicated for use in patients aged 12-64 for evaluation of acute respiratory infection who have had symptoms for less than 7 days and within 3 days of fever onset.

FebriDx test results are intended to be used in conjunction with other clinical and diagnostic findings as an aid in the diagnosis of bacterial acute respiratory infection and differentiation from non-bacterial etiology. The assessment of whether a bacterial infection is present should always be based on consideration of all available information, and not based solely on the FebriDx test results. FebriDx test results are not intended to identify a specific pathogen or the severity of infection.

For in vitro diagnostic use

For prescription use only

C Special Conditions for Use Statement(s):
Rx - For Prescription Use Only

D Special Instrument Requirements:
None.

IV Device/System Characteristics:

A Device Description:

FebriDx is a 10-minute lateral flow assay that detects Myxovirus resistance protein A (MxA) and C-reactive protein (CRP) in patient fingerstick samples to aid in the evaluation of an infection in patients presenting with acute respiratory symptoms.

The single-use disposable FebriDx test includes a lateral flow test strip, a built-in retractable safety lancet, blood collection and transfer tube, and buffer delivery system

B Principle of Operation:

The FebriDx test includes a built-in sample collection and transfer tube detects the presence of MxA and CRP in fingerstick blood specimens using lateral flow technology. A sample fingerstick blood is added to the lateral flow test device followed by a running buffer that provides sufficient volume to activate the test. The running buffer contains leukocyte membrane lysing agents that release intracellular MxA to allow subsequent detection. The first pad in the device filters out the

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cellular material as well as intact red-blood cells. The filtered sample then contacts a pad that contains the reagents to adjust pH and reduce potential non-specific binding. Prior to reaching the test strip, free MxA and CRP migrate through a dried formulation of latex beads that have been further conjugated to antibodies specific for binding a particular analyte (MxA or CRP). As the analyte-antibody-bead complex continues to migrate across a porous nitrocellulose membrane, it can interact with one of three capture antibodies that are immobilized on the surface at distinct line positions, including the control line to verify that the sample flowed properly across the device. In the presence of a valid blue control line, the FebriDx test result may be interpreted as one of two different outcomes: the presence of a single black line in the result window indicates a positive bacterial infection result whereas a red line in the result window or the absence of any line in the result window indicates a non-bacterial etiology

V Substantial Equivalence Information:

A Predicate Device Name(s):

FebriDx Bacterial / Non-Bacterial Point-of-Care Assay

B Predicate 510(k) Number(s):

K230917

C Comparison with Predicate(s):

| Device & Predicate Device(s): | K260787 | K230917 |
| --- | --- | --- |
| Device Trade Name | Same | FebriDx Bacterial / Non-Bacterial Point-of-Care Assay |
| General Device Characteristic Similarities | | |
| Intended Use/Indications For Use | The FebriDx Bacterial/Non-Bacterial Assay is a qualitative visually read rapid immunoassay for the detection of human host response proteins, Myxovirus resistance protein A (MxA) and C-reactive protein (CRP) directly from fingerstick blood. FebriDx is indicated for use in patients aged 12-64 for evaluation of acute respiratory infection who have had symptoms for less than 7 days and within 3 days of fever onset.
FebriDx test results are intended to be used in conjunction with | The FebriDx Bacterial/Non-Bacterial Point-of-Care Assay is a qualitative visually read rapid immunoassay for the detection of human host response proteins, Myxovirus resistance protein A (MxA) and C-reactive protein (CRP) directly from fingerstick blood. FebriDx is indicated for use in patients aged 12-64 who present to urgent care or emergency care settings for evaluation of acute respiratory infection who have had symptoms for less than 7 days and within 3 days of fever onset. |

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| | other clinical and diagnostic findings as an aid in the diagnosis of bacterial acute respiratory infection and differentiation from non-bacterial etiology. The assessment of whether a bacterial infection is present should always be based on consideration of all available information, and not based solely on the FebriDx test results. FebriDx test results are not intended to identify a specific pathogen or the severity of infection.
For in vitro diagnostic use
For prescription use only | FebriDx test results are intended to be used in conjunction with other clinical and diagnostic findings as an aid in the diagnosis of bacterial acute respiratory infection and differentiation from non-bacterial etiology. The assessment of whether a bacterial infection is present should always be based on consideration of all available information, and not based solely on the FebriDx test results. FebriDx test results are not intended to identify a specific pathogen or the severity of infection.
For in vitro diagnostic use
For prescription use only |
| --- | --- | --- |
| Measurand | Same | MxA/CRP |
| Test Type | Same | Lateral Flow
Immunochromatographic Assay |
| Components | Same | All-in-one cassette with lateral flow test strip, safety lancet, blood collection and transfer tube, and buffer delivery system. |
| External Controls | Same | External positive and negative controls available |
| Measurement | Same | Qualitative |
| Device Format | Same | Single-use disposable |
| Sample Type | Same | Fingerstick blood |
| Sample Volume | Same | 5 μL |
| Equipment | Same | Visually read |
| Result Time | Same | Minimum of 10 minutes, up to 1 hour |

VI Standards/Guidance Documents Referenced:

Not applicable.

VII Performance Characteristics (if/when applicable):

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# A Analytical Performance:

1. Precision/Reproducibility:

Reproducibility of the FebriDx test was established previously. The device is unchanged from the predicate and additional studies were not required. Please refer to the public decision summary for K230917.

2. Linearity:

Not applicable.

3. Analytical Specificity/Interference:

Interference from endogenous and exogenous sources was established previously. The device is unchanged from the predicate and additional studies were not required. Refer to the public decision summary for K230917.

4. Detection Limit and Assay Reportable Range:

The limit of detection for analytes detected by the FebriDx test were established previously. The device is unchanged from the predicate and additional studies were not required. Refer to the public decision summary for K230917.

Assay reportable range is not applicable.

5. Traceability, Stability, Expected Values (Controls, Calibrators, or Methods):

External controls and reagent stability were evaluated previously. The device is unchanged from the predicate and additional studies were not required. Refer to the public decision summary for K230917.

6. Assay Cut-Off:

Not applicable.

# B Comparison Studies:

1. Method Comparison with Predicate Device:

Please refer to section VII.C (Clinical Studies) below for the clinical validation regarding the method comparison studies.

2. Matrix Comparison:

Not applicable.

# C Clinical Studies:

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1. FebriDx performance with trained users:

The FebriDx test was previously cleared (K230917) based on results from a prospective, multi-center, blinded clinical study. The clinical performance of the FebriDx test was determined in patients presenting to a primary care provider, urgent care clinic, or the Emergency Department with signs/symptoms of acute respiratory infection and a recent fever. FebriDx clinical performance was evaluated against results of a clinical reference algorithm in conjunction with adjudication by two independent expert reviewers.

2. FebriDx performance with untrained users:

To support use in CLIA waived settings, a user comparison study was conducted to show that FebriDx has comparable performance in the hands of untrained operators in waived settings. The clinical performance of the FebriDx test in waived settings was evaluated in a multi-center, prospective clinical study between December 2024 and July 2025. Nine clinical sites in geographically distinct regions of the U.S. (Southeast, Midwest, and West) representative of CLIA-waived intended use sites, including physician offices, primary care/outpatient clinics, and urgent care centers participated in the study. At each site, both trained and untrained operators collected a paired fingerstick sample from the same subject, with operators blinded to each other's results. FebriDx performance in the hands of untrained operators was compared to device performance with trained operator results and Positive Percent Agreement (PPA), Negative Percent Agreement (NPA) and confidence intervals were calculated.

a. Operators:

Sixteen untrained operators (1-3 per site) and 16 trained operators (1-2 per site) collected paired fingerstick samples from the same study subject. To avoid bias, the trained and untrained operators performed the FebriDx testing and result interpretation during the same visit but in separate spaces where they could not see the other operator. The untrained operators were representative of the CLIA-waived intended user population. The education level of the untrained operators included high school diploma, associate degree, or university education, and included clinical and administrative staff who performed various tasks in the CLIA waived setting (medical and research assistants, nurses, and phlebotomists). Information on the operators' current job title, education level and any laboratory or relevant work experience was provided. The untrained operators did not receive any training on the use of the FebriDx test and had no hands-on experience with conducting diagnostic testing in a clinical laboratory. Trained operators met the qualifications to perform CLIA moderate to high complexity testing. FebriDx performance in the hands of untrained operators was compared to performance of the trained operators.

b. Subjects:

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A total of 610 subjects were enrolled initially, of which 595 met the inclusion criteria summarized below:

## Inclusion Criteria:

- Subject is willing to provide written informed consent.
- Subject is 12-64 years of age.
- Subject exhibits or reports a new onset measured temperature (oral or tympanic) of greater than or equal to $100.5^{\circ}\mathrm{F} / 38^{\circ}\mathrm{C}$ within 3 days (72 hours) of enrollment or at the visit.
- Subject has clinical suspicion for Acute Respiratory Infection and presents with at least one (1) of the following new onset symptoms beginning $\leq 7$ days of enrollment - runny nose, nasal congestion, sore throat, cough, hoarse voice or shortness of breath.

## Exclusion Criteria:

- Subject is unable or unwilling to provide signed informed consent.
- Subject is less than 12 years old or over 64 years old.
- Subject has a fever that started more than 3 days prior to enrollment.
- Subject has symptoms of Acute Respiratory Infection that started &gt; 7 days of enrollment.
- Subject is receiving interferon therapy in the last 30 days.
- Subject is in an immunocompromised state or taking immunosuppressive or chemotherapeutic medications in the last 30 days.
- Subject has taken antibiotics or antiviral therapy in the last 14 days.
- Subject received a live viral immunization in the last 14 days.
- Subject has significant trauma or burns (&gt; 5% total body surface area or full thickness (3rd°)) in the last 30 days.
- Subject has had major surgery in the last 30 days.
- Subject has a history of a myocardial infarction or stroke in the last 30 days.

The clinical study protocol included an enriched enrollment phase if the minimum number of positive samples were not obtained during all-comer enrollment. Sites that participated in enriched enrollment screened patients for all-comer inclusion/exclusion criteria as well as the enriched criteria: fever of $100.5^{\circ}\mathrm{F}$ (either within the last 72 hours or at the study visit) and a bacterial-positive test result, or a negative respiratory viral test result, or antibiotics prescribed to the subject on the day of enrollment by the treating clinician at the standard of care visit, or a bacterial positive FebriDx test interpreted by a trained operator. To mitigate potential interpretation bias and maintain operator blinding, every third subject with a negative FebriDx test result was asked to participate in the enrichment phase.

The demographic summary of the clinical subjects is shown in Table 4 below.

Table 4: Demographic Information for Study Subjects
| Study Participants (N = 554) |
| --- |
| Gender |

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| Female | 326 (58.4%) |
| --- | --- |
| Male | 228 (41.2%) |
| Age Group (Years) | |
| 12-17 years | 16 (2.9%) |
| 18-25 years | 66 (11.9%) |
| 26-45 years | 242 (43.7%) |
| 46-64 years | 230 (41.5%) |
| Race | |
| Asian | 7 (1.3%) |
| Black/African American | 69 (12.5%) |
| White | 462 (83.4%) |
| Other | 16 (2.89%) |
| Ethnicity | |
| Hispanic | 263 (47.5%) |
| Non-Hispanic | 2912.5%) |

c. Results:

i. Of the 610 subjects initially enrolled, 595 met the inclusion criteria. There were 41 patients re-enrolled for the enrichment phase, yielding 554 unique subjects. A total of 1216 FebriDx tests were performed (608 tests from untrained users and 608 tests from trained users). There was a total of 26 (2.1%, 95% CI 1.5-3.1%) invalid test results (13 (50%) from untrained users and 13 (50%) from trained users). All operators correctly identified the invalid test and re-ran the test as per the instructions in the QRI. Upon re-testing, all 26 tests were valid, resulting in a final invalid rate of 0% (0/1216) with 95% CI (0-0.3%).

ii. The clinical performance of the FebriDx test with fingerstick specimens, when used by untrained operators in CLIA-waived settings, is shown in Table 5 and presented as positive and negative percent agreement compared to the trained operator. The results from the user comparison study support acceptable FebriDx test performance in the hands of untrained users in CLIA-waived environments and an insignificant risk of erroneous results.

Table 5. FebriDx Clinical Performance with Untrained Users

| | FebriDx Test Result (Trained Operator) | | |
| --- | --- | --- | --- |
| FebriDx Test Result (Untrained Operator) | Bacterial | Non-Bacterial | Total |
| Bacterial | 106 | 8 | 114 |
| Non-Bacterial | 1 | 480 | 481 |
| Total | 107 | 488 | 595 |
| Positive Percent Agreement | 99.1% (95% CI 94.4% - 99.8%) | | |
| Negative Percent Agreement | 98.4% (95% CI 96.8% - 99.2%) | | |

1. Clinical Cut-Off:

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Not applicable.

## D Expected Values/Reference Range:

Expected values/reference range for the FebriDx test were established previously. The device is unchanged from the predicate and additional studies were not required. Refer to the public decision summary for K230917.

## VIII Proposed Labeling:

The labeling supports the finding of substantial equivalence for this device.

## IX Conclusion:

The submitted information in this premarket notification is complete and supports a substantial equivalence decision.

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