From the Guidelines
To diagnose cat scratch disease, you should order a PCR test that specifically targets Bartonella henselae DNA. This test can be performed on tissue samples from lymph node aspirates or biopsies, or on blood samples in cases of suspected systemic infection. The PCR test for Bartonella henselae offers higher sensitivity and specificity than traditional serologic testing, particularly in early infection stages 1. When ordering the test, specify that you're looking for Bartonella henselae, as this is the primary causative agent of cat scratch disease.
Some key points to consider when ordering the PCR test include:
- The sample should be collected before antibiotic treatment begins, as antimicrobials can reduce the bacterial load and potentially lead to false-negative results.
- PCR testing is particularly valuable in cases where the clinical presentation is atypical or when a rapid diagnosis is needed.
- The test works by amplifying specific segments of the Bartonella henselae genome, allowing for detection of even small amounts of bacterial DNA in clinical specimens, making it an excellent diagnostic tool for confirming cat scratch disease 1.
It's also important to note that while azithromycin is recommended for the treatment of cat scratch disease 1, the diagnosis should be confirmed through PCR testing or other means before initiating treatment.
From the Research
Diagnosis of Cat Scratch Disease
To diagnose cat scratch disease, a blood test using Polymerase Chain Reaction (PCR) can be ordered to detect the presence of Bartonella henselae, the bacterium responsible for the disease 2.
Recommended PCR Test
The specific PCR test to order is not specified in the provided studies, but it is recommended to use a test that targets the Bartonella henselae gene, such as the 16S rRNA gene or the groEL gene.
Alternative Diagnostic Methods
Alternatively, serologic tests such as immunoglobulin G (IgG) and immunoglobulin M (IgM) antibody tests can be used to diagnose cat scratch disease 3, 4, 5. However, these tests may have limitations, such as low sensitivity and specificity, and may require convalescent serum testing to confirm the diagnosis 4.
Key Considerations
When ordering a PCR test or serologic test, it is essential to consider the following:
- The patient's clinical presentation and history of exposure to cats
- The sensitivity and specificity of the test
- The potential for false-negative or false-positive results
- The need for convalescent serum testing to confirm the diagnosis
Available Tests
Some available tests for diagnosing cat scratch disease include: