What is a PSE test, and how accurate is it?

The PSE test refers to a Prostate-Specific Episwitch test, a new precision medicine tool used to evaluate the presence of prostate cancer. This test was developed in the UK by Oxford university scientists and clinically validated by clinician scientists from Imperial College (Matt Winkler) and East Anglia University (Dmitry Pshezhetskiy). It measures a person's epigenetic signature, which is how our genes are expressed throughout our lives under the influence of the environment, lifestyle and diet.

How is a PSE test performed?

The test usually involves the following steps:

• Specific consent process: In line with regulation for use of a person's epigenetic information. This is done face-to-face with the specialist just before the sample is obtained by the nurse.
• Sample collection: A conventional blood sample is obtained.
• Laboratory analysis: The collected sample is tested in Oxford Biodynamics (OBD) PLC's certified laboratory.
• Complementary tests: The PSE test routinely includes the prostate-specific antigen (PSA) tests and often combined with imaging like prostate MRI, to confirm findings.

How accurate is the 'precision medicine' PSE test?

While the PSE test can provide valuable information, its accuracy depends on the context and how it's interpreted:

• Accuracy: This precision medicine test has an accuracy of 94 per cent, which is at least twice as good as the conventional PSA test. Only six per cent of men who have the test are incorrectly diagnosed.
• Sensitivity: 86 per cent, which means the test is effective in identifying most men with prostate cancer. Specifically, 9 out of 10 men with prostate cancer are correctly identified.
• Specificity: 97 per cent, which means more than 19 out of 20 men with no prostate cancer are correctly identified as such. This avoids many unnecessary follow on tests, including biopsies.
• Limitations: It isn't a standard diagnostic tool in the UK yet. False positives or negatives may occur, especially if the sample is insufficient or there are other underlying factors, such as infections or inflammation. 
• Enhanced accuracy: The PSE test has an accuracy of 94 per cent which is twice as good as the conventional PSA test. When combined with other diagnostic methods like PSA levels and prostate MRI, it contributes to a more comprehensive evaluation of prostate health. Infection, inflammation, recent intervention, prostate size, intimacy and heavy exercising do not affect this test. Government insurance programs Medicare and Medicaid in the USA use this test routinely, and 40 million men benefit from it. 

For men experiencing symptoms such as difficulty urinating, pelvic discomfort or blood in the urine, consulting a urology specialist and discussing the potential role of the PSE test can be an essential step toward diagnosis and treatment. It may avoid further downstream tests such as unnecessary prostate MRI or prostate biopsy.

What is a good indication for a PSE test?

• If you're between 45 and 75, never have had a PSA test and are in a high risk demographic such as men in the Black ethnic group, or have a positive family history of prostate, breast and ovarian cancer.
• To improve accuracy of the PSA test and avoid unnecessary MRI scans and prostate biopsies; i.e.: mildly elevated PSA tests are frequently false-positive due to factors like inflammation, infection, intimacy or exercise. 
• To decide if you need a prostate biopsy if you have an elevated PSA and an equivalent MRI scan (score 3).
• To find out if a prostate cancer has been missed when the PSA and the MRI are abnormal, and the prostate biopsy shows no cancer cells.
• To find out if you need a repeat MRI or prostate biopsy when previous tests have been negative, but the PSA remains elevated.

What happens when a PSE test is positive? Does this mean there's a high probability of prostate cancer?

A positive PSE test triggers a prostate MRI (unless this was done already) and a prostate biopsy. This is necessary to create a tailored treatment plan which typically includes:

• Further diagnostic tests after prostate cancer is identified: Additional imaging such as CT scans, bone scans and PSMA PET CT scans may be necessary.
• Treatment planning: Based on the severity of the diagnosis, options may include active surveillance with lifestyle changes, or procedures such as robotic keyhole surgery or focal ablative therapies or radiotherapy.
• Monitoring and follow-up: Regular follow-up appointments are essential to track progress and ensure the effectiveness of treatment. This may include repeating the PSA test, MRI scans or other relevant diagnostics over time.
• Cost: The total cost are dictated by the company OBD PLC and come to £1,000. This includes counselling, consent, sample taking, courier transfer, analysis and communication of results. The test results are available within seven days.

Early diagnosis and proactive management are crucial for improving outcomes, and the PSE test plays an important role in guiding effective care.