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The Directigen™ EZ Flu A+B test is a rapid chromatographic immunoassay for the direct and qualitative detection of influenza A and B viral antigens from nasopharyngeal washes/aspirates, nasopharyngeal swabs and throat swabs of symptomatic patients. The Directigen EZ Flu A+B test is a differentiated test, such that influenza A viral antigens can be distinguished from influenza B viral antigens from a single processed sample using a single device. The test is to be used as an aid in the diagnosis of influenza A and B viral infections. All negative test results should be confirmed by cell culture because negative results do not preclude influenza virus infection and should not be used as the sole basis for treatment or other management decisions.

Influenza illness classically presents with sudden onset of fever, chills, headache, myalgias, and a non-productive cough. Epidemics of influenza typically occur during winter months with estimated 114,000 hospitalizations¹ and 36,000 deaths² per year in the U.S. Influenza viruses can also cause pandemics, during which rates of illness and death from influenza-related complications can increase dramatically.

Patients who present with suspected influenza may benefit from treatment with an antiviral agent especially if given within the first 48 h of onset of illness. It is important to rapidly distinguish influenza A from influenza B in order to allow physicians a choice in selective antiviral intervention. Moreover, it is important to determine if influenza A or B is causing symptomatic disease in a particular institution (e.g., nursing home) or community, so that appropriate preventative intervention can be taken for susceptible individuals. It is therefore important to not only rapidly determine whether influenza is present, but also which type of influenza virus is present.

Diagnostic tests available for influenza include rapid immunoassay, immunofluorescence assay, polymerase chain reaction (PCR), serology, and viral culture.^3-10 Immunofluorescence assays entail staining of specimens immobilized on microscope slides using fluorescent-labeled antibodies for observation by fluorescence microscopy.^5,11,12 Culture methods employ initial viral isolation in cell culture, followed by hemadsorption inhibition, immunofluorescence, or neutralization assays to confirm the presence of the influenza virus.^12-14

The Directigen EZ Flu A+B test is a chromatographic immunoassay to detect influenza A or B antigens from respiratory specimens of symptomatic patients with time to results of 15 min.

The speed and simplified workflow of the Directigen EZ Flu A+B test make it applicable as a "STAT" influenza A and B antigen detection test providing relevant information to assist with the diagnosis of influenza. The use of the Directigen EZ Flu A+B test to differentiate Flu A from Flu B infection can provide the opportunity for greater selectivity of antiviral intervention.

Quality control requirements must be performed in accordance with local, state and/or federal regulations or accreditation requirements and your laboratory's standard Quality Control procedures.

Each Directigen EZ Flu A+B device contains both positive and negative internal/procedural controls:

- The appearance of a reddish purple control line in the Flu A and/or Flu B read windows at the Control "C" position provides an internal positive control that validates the proper reagent function and assures that the correct test procedure was followed.
- The membrane area surrounding the Flu A and/or Flu B test and control lines is the internal negative control for the device. A background area that is white to light pink indicates that the test is performing correctly.

Each Directigen EZ Flu A+B kit contains swab Control A+/B- and B+/A-:

These controls are tested in the same manner as patient specimens and provide a means of external quality control. At a minimum, these controls should be run as a quality control procedure for each new kit lot or shipment received. If desired, appropriate reagent performance and proper testing technique may also be determined by using specimens qualified as positive or negative for the influenza A or B virus.

The formation of a reddish purple line on the membrane in the Flu A read window at the Test (T) position and Control (C) position when the A+/B- Control is tested, and in the Flu B read window at the Test (T) position and Control (C) position when the B+/A- Control is tested, indicates that the influenza antigen binding property of the test strip is functional.

The formation of a reddish purple control line at the Control (C) position in the Flu B read window and the absence of a reddish purple test line at the Test (T) position when the A+/B- Control is employed is an appropriate Flu B negative control result that indicates proper reagent function and that the proper test procedure was followed. Similarly, the formation of a reddish purple control line at the Control (C) position on the Flu A read window and the absence of a reddish purple test line at the Test (T) position when the B+/A- Control is tested indicates an appropriate Flu A negative control result.

If the kit controls do not perform as expected, do not report patient results. Contact your local BD representative or Technical Services for assistance.

The following components are included in the Directigen EZ Flu A+B kit:

For in vitro Diagnostic Use.

1. If infection with a novel influenza A virus is suspected based on current clinical and epidemiological screening criteria recommended by public health authorities, specimens should be collected with appropriate infection control precautions for novel virulent influenza viruses and sent to state or local health departments for testing. Viral culture should not be attempted in these cases unless a BSL 3+ facility is available to receive and culture specimens.

2. Pathogenic microorganisms, including hepatitis viruses, Human Immunodeficiency Virus and novel influenza viruses, may be present in clinical specimens. "Standard Precautions"^15-18 and institutional guidelines should be followed in handling, storing and disposing of all specimens and all items contaminated with blood and other body fluids.

3. Reagents contain sodium azide, which is harmful if inhaled, swallowed or in contact with skin. Contact with acids liberates very toxic gas. If there is contact with skin, wash immediately with plenty of water. Sodium azide may react with lead and copper plumbing to form highly explosive metal azides. On disposal, flush with a large volume of water to prevent azide build-up.

4. Do not use kit components beyond the expiration date.

5. Do not mix reagents from different kit lot numbers.

6. Do not reuse the device.

7. Do not use the kit if the Controls do not yield appropriate results.