IHC Marker - PAX 8 Test

The PAX 8 test detects the expression of the PAX8 nuclear protein in tumour cells. A pathologist examines the stained tissue to assess whether PAX8 is present and how widely it is expressed across the sample. The results are interpreted as follows:

The PAX 8 test procedure does not require any special preparation from the patient, as the sample is a tissue block rather than blood or urine. However, there are a few important steps to be aware of before and during the process.

Do You Need to Fast?

No fasting is required for this test. It is a tissue-based test and is not affected by food or drink intake.

Practical Tips Before Your Test

Here are a few practical points to keep in mind:

• Bring a detailed clinical history, including your symptoms, previous test results, and family history, as this is required for the test
• Inform your doctor about any prior biopsies, surgeries, or procedures related to the suspected tumour
• Ask your doctor whether the tissue block from a previous biopsy or surgery can be used, as a fresh biopsy may not always be needed
• Paraffin sections are best cut within six weeks of embedding, so inform the lab if the block is older
• No dietary or medication restrictions apply for this test

Step-by-Step Procedure

The process for the IHC marker - PAX 8 test involves several laboratory steps after tissue collection:

1. A tissue sample is obtained through biopsy or from a surgical specimen already removed during an operation, and fixed in formalin to preserve the tissue.
2. The fixed tissue is embedded in paraffin wax to create a firm block, known as an FFPE tissue block, which is then sent to the laboratory.
3. In the lab, thin sections are cut from the block, mounted on glass slides, and processed through antigen retrieval to make the PAX8 protein detectable.
4. The tissue sections are incubated with a PAX8-specific antibody, which binds to the PAX8 protein if it is present in the cells.
5. A secondary antibody and staining reagents are applied, making the bound PAX8 protein visible as a brown or coloured deposit under the microscope.
6. A qualified pathologist examines the stained slides, assesses the pattern and intensity of nuclear staining, and reports the result in the context of your clinical history.

Factors That Can Affect Accuracy

Several technical factors can influence the quality of staining and the reliability of results:

• Quality and duration of tissue fixation in formalin before embedding
• Age of the paraffin section (sections older than six weeks may show reduced staining)
• Type of antibody used (monoclonal versus polyclonal)
• Quality and surface chemistry of the glass slides used
• Adequacy of the tissue sample obtained during biopsy

Because this is a diagnostic marker test rather than a routine screening test, there are no "healthy" or "unhealthy" levels to maintain. The following points, however, are useful after receiving your results:

• Follow up promptly with your oncologist or treating specialist to discuss what the results mean for your care.
• Share all previous investigation reports and imaging results with your doctor for a complete picture.
• Keep open communication with your healthcare team throughout the diagnostic process.