Bartonella infections are mostly associated with fleas, lice, or the scratch of a small animal such as a cat – but they are also transmitted through tick bites. Like the tests for Lyme disease and other tick-borne diseases, some Bartonella tests are more reliable than others. In this article, learn about the limitations of the Bartonella IFA and why the Bartonella ImmunoBlot is better, especially when performed alongside FISH and PCR tests.
Diagnosing Bartonellosis
Cat Scratch Disease (CSD), one of several diseases caused by species of Bartonella, can often be diagnosed based only on the patient’s symptoms and history – e.g., if the patient was bitten by a tick or scratched by a small animal and is now experiencing symptoms of CSD. However, laboratory tests are important tools for confirming infections and detecting any cross-reaction with other species of Bartonella that can be transmitted by ticks.
Traditionally, these laboratory tests include:
- Indirect Immunofluorescent Assays (IFA)
- Polymerase Chain Reactions (PCR)
- Fluorescent In-Situ Hybridization (FISH)
- Western Blots
However, limitations in some of these Bartonella tests – particularly Western Blots and IFA tests – have led IGeneX to develop a better, more reliable test: the ImmunoBlot for Bartonella. Like the ImmunoBlot for Lyme disease, the Bartonella ImmunoBlot uses recombinant antigens, preventing many of the accuracy issues that come with using lab-grown or commercially bought organisms.
Keep reading to learn more about how the ImmunoBlot works and why it’s more sensitive, specific, and efficient than the Western Blot and IFA.
Bartonella IFA vs. Bartonella ImmunoBlot: Which is better?
How IFA works
The Indirect Immunofluorescent Assay (IFA) is an antibody test performed on a patient’s blood. In an IFA, antigens – usually proteins – from the pathogen are placed on a glass slide, and then the patient’s serum is added. If the patient’s serum has antibodies to the Bartonella organism, then they will bind to the slide.
Finally, a secondary antibody that contains a fluorescent dye is added. This secondary antibody binds to the patient’s antibody. The slide is then looked at under a microscope that uses a black light source to see if anything is glowing. Glowing spots indicate a positive test.
Limitations of the IFA
The testing methodology of the IFA has several potential problems, including:
Problems with the antigen source
As mentioned, an IFA relies on either lab-grown or commercially-bought antigens. The quality and purity of the culture used can affect the quality of the antigens and thus the accuracy of the test results. Additionally, the number of Bartonella species available to culture or buy commercially is limited.
Lack of specificity & sensitivity
Like the Western Blot for Lyme and other tick-borne diseases, IFA can cause false positives if other things in the patient’s serum light up when the serum is added to the slide.
Not only can the results be affected by the presence of other things in the patient’s serum besides Bartonella antibodies, but also, many IFA tests are not sensitive enough to detect all the possible species of Bartonella that can cause infection. Again, there are generally no genus-specific proteins available to culture, so the IFA can miss infections if the patient was infected by a species not included in the culture used.
Technical limitations
IFA is a manual test requiring lots of time and resources to perform. Lab technicians have to be specially trained to perform the test, which involves looking through a microscope for a specified amount of time and interpreting the results visually.
Obviously, this comes with several potential problems:
- Results are subject to human error due to inadequate training or experience, technician illness or fatigue, etc.
- Results can vary depending on the age of the specimen, the age of the slide, and how the slide was stored prior to analysis (e.g., a storage temperature that was too high or too low).
- Results can vary depending on the age of the fluorescent bulb in the microscope – it’s not uncommon for lab technicians to be completely unaware that the fluorescent bulb is not working, leading to false negatives.
How the ImmunoBlot differs
The ImmunoBlot’s design corrects many of the limitations of IFA and Western Blots mentioned above. For one thing, the use of recombinant agents (rather than lab-grown or commercially-bought antigens) allows for genus-specific testing, making the tests much more specific and sensitive to a wider range of Bartonella species.
The ImmunoBlot also does not rely on the manual analysis of a slide through a microscope. Instead, recombinant agents are sprayed onto test strips in precise amounts and specific locations. The quantity and location of the antigens are tightly controlled by a printing-like process, eliminating many of the potential human errors and equipment problems that come with the manually-run IFA and Western Blots. In fact, the Western Blot has been eliminated altogether from the IGeneX Bartonella test panel in favor of the more reliable ImmunoBlot.
Advantages of the ImmunoBlot
- Allows for identification of a broad range of Bartonella species, including B. henselae, B. quintana, B. elizabethae, and B. vinsonii
- Detects multiple species in one test, unlike IFA which detects one species at a time
- Uses specifically created recombinant proteins and not proteins from cell cultures
- Detects the full spectrum of disease: early, active, and late-stage disease
- Can be made genus and species-specific
- Quantity and location of the antigens are controlled by a printing-like process, improving consistency and specificity
- Avoids the old-fashioned, manual, error prone and time-consuming process of visualizing glass slides through a microscope
- Renders Western blot and IFA obsolete, and is meant to replace them
The importance of panel testing
If the ImmunoBlot works so much better than older styles of testing, what is the value of the other types of tests offered by IGeneX, such as FISH and PCR tests? In short, the most reliable way to test for Bartonella is with a full panel. The ImmunoBlot works best when used alongside a FISH and PCR. The complimentary use of different testing methods offers the best chance of confirming a Bartonella infection.
Learn more about the Bartonella tests available at IGeneX today.
