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Overview
  • Current flu diagnostics are based on two different technologies:
    1) Antigen Detection with Antibodies and
    2) Neuraminidase (NA) Activity Detection
  • Antigen Detection with Antibodies may miss strain changes due to mutation of the influenza virus
  • The ZstatFlu test is based on NA Activity Detection, which is inherently more reliable for detecting the various strains and subtypes of influenza
  • NA Activity Detection is based on some of the same principles as the new influenza therapeutics

The ZstatFlu™ Technology Advantage

Point-of-care viral diagnostics are few, and for influenza you can count these on one hand minus a couple fingers. The recent introduction of therapeutics will likely increase the number of diagnostics for influenza, but what are the current and future diagnostics detecting and how do they do it?

Why would this information be important? Before filling up your automobile would you want to know if your car has a gasoline or diesel engine? If you purchase software, would it be important to know if it ran on a Mac OS or DOS operating system? If you paid for a prescription drug, would it be important to know that the infection you are being treated for is really what you are suffering from?

Detection Methods

Influenza diagnostics at the point of care and in the clinical laboratory currently use two "operating systems" for detection of this virus. They include:
  1. Antigen Detection with Antibodies
  2. Neuraminidase (NA) Activity Detection
Influenza Evades the Immune System

To understand the significance of these two detection methods, you must first be acquainted with the influenza virus and how it replicates. Influenza virus is interesting among the viruses in that it can infect humans, chickens, pigs, horses, seals and a host of other animals. In fact, this virus can simultaneously infect pigs with a pig strain, a bird strain and a human strain. Once multiple viral infections occur, influenza can shuffle its genes between these different strains and emerge as a more potent virus that is potentially more lethal than any of the former strains. Influenza virus can also mutate in a similar way that HIV mutates. These are the two ways the influenza virus evades our immune system, which is the primary reason for annual influenza immunizations using a different vaccine each year.

Antigen Detection with Antibodies

This method of detection uses antibodies, not from humans, but from mice that have been immunized with influenza. Unfortunately, the use of antibodies to detect influenza suffers from the same problem that the immune system faces in fighting the infection - mainly the problem of detecting a mutated target.

Neuraminidase (NA) Activity Detection

This detection method uses a more stable target and has been shown to be unaffected by the viral mutations that have occurred over many decades. It recognizes a "groove" inside the NA enzyme that cannot be reached by antibodies. Because this NA activity is important for the virus to be infectious, the virus has saved the critical parts of this NA "groove". The ZstatFlu test uses a chemical that fits into this "groove" and forces the virus to expose itself by reacting to the chemical. This is the same technology used by the new influenza therapeutics, however instead of reacting to the chemical, the NA is inhibited by the chemical therapeutic.

Feature Comparison of Detection Methods

 Antigen Detectionwith AntibodiesNeuraminidase (NA) Activity Detection
Historically safe from mutations for both type A and BNoYes
Technology matched with new therapeuticsNoYes
Shown to detect emerging strains of Hong Kong FluVariableYes
Previously demonstrated 99% specificityNoYes
Detects all existing types and strains of influenza VariableVariableYes

Current Point-of-Care Diagnostic Tests For Influenza

On the market today, there are four diagnostic tests for influenza: Flu OIA® from BioStar, Directigen® Flu A from Becton-Dickenson, QuickVue® from Quidel and ZstatFlu® from ZymeTx. The Flu OIA, Directigen Flu A and QuickVue tests all use the Antigen Detection with Antibody method. The ZstatFlu test is the only test that uses the Neuraminidase (NA) Activity method of detection. The ZstatFlu test was invented by ZymeTx and is protected by multiple US and foreign patents.

The ZstatFlu Advantage

The Neuraminidase (NA) Activity Detection method is a superior technology for the detection of influenza compared to the Antigen Detection by Antibodies method. NA Activity Detection is based upon a technology that we call "Endogenous Viral-encoded Enzyme Assay (EVEA)" and is the latest in the development of technologies for diagnostics since the introduction of Polymerase Chain Reaction (PCR) in 1985.

In addition to providing the above advantages, the ZstatFlu test requires less than two minutes hands-on time for the user. The ZstatFlu test is also a part of a comprehensive Influenza Disease Management Program developed by ZymeTx which includes real-time influenza disease surveillance and index case management.

When you choose an influenza diagnostic, doesn't it make sense to use the one that gives you the greatest assurance that a positive test means that it's really the flu?
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