Fingerprick PSA Test Has In-Office Results in 12 Minutes

First of Its Kind Approved by FDA

Nick Mulcahy

April 17, 2019

Instead of waiting days or even weeks for the result of a prostate-specific antigen (PSA) test, physicians and their patients can now have the information in minutes, thanks to a novel device recently approved by the US Food and Drug Administration.

The Sangia Total PSA Test (OPKO Diagnostics) is the first test that can provide PSA results at the point of care rather than via a remote laboratory.

"The test can be administered with a simple finger prick, and results are generated in less than 15 minutes," said the FDA in its approval notice on January 30, adding that the process takes 10 to 12 minutes.

The Sangia test quantitatively measures total PSA in capillary whole blood. The test is approved to be used with digital rectal examination (DRE) to screen for prostate cancer in men aged 50 years or older.

The device includes a "microfluidic" immunoassay in a credit card-sized disposable test cassette and features proprietary Silver Amplified NeoGold ImmunoAssay (Sangia) technology. During the testing process, a fingerstick blood sample is collected and fills into the device's sample collector which, in turn, connects to the casette that is inserted to the tool's analyzer.

There are 25 million PSA tests performed in the US annually, says OPKO.

"The advantages of this approach for the patient are knowing the test result 'while you wait,' getting just a finger stick, not having to go to a separate laboratory facility, and receiving just one 'global' bill for both the doctor visit and the test," said Lawrence Wyner, MD, a urologist at Marshall University, Huntington, West Virginia, who was asked for independent comment.

The efficacy of the test was demonstrated in a clinical trial at 10 urology practices in the US, among 434 men (median age 65 years) who were scheduled to receive a prostate biopsy.

In the cohort, the median total PSA was 5.9 ng/mL, and the eventual prevalence of prostate cancer was 53.7%.

With a total PSA cut-off value of 4 ng/mL, which is considered the lower limit of a suspicious amount, the sensitivity of the Sangia Total PSA Test was 85.4% and the specificity, 30.3%. When combined with DRE, the test's sensitivity increased to 91%.

Additionally, the unique point-of-service test had a 95% correlation with a previously FDA-approved, lab-based test (Elecsys Total PSA Immunoassay, Roche Diagnostics) in a set of blood samples from 122 men.

The device measures total PSA values between 0.08 ng/mL and 15 ng/mL. For values above or below these two points, the device simply indicates either <0.08 ng/mL or >15 ng/mL.

The test requires disposables (not included) such as exam gloves, alcohol swab, gauze pad, bandage, and a sterile, single-use lancet (sufficient to collect at least 20μL of blood).

The CLIA Factor

The new point-of-care test has "the potential to improve patient care across a range of clinical contexts," write Alexa Meyer, MD, and Michael Gorin, MD, urologists at Johns Hopkins University, Baltimore, Maryland, in a product review published April 4 in Nature Reviews Urology.

In the setting of prostate cancer screening, the Sangia test could potentially "accelerate care by enabling PSA testing and downstream decision-making to occur in a single clinical encounter," they write.

In turn, physicians and patients could have "immediate discussion" of next steps, such as undergoing an MRI or prostate biopsy.

Meyer and Gorin do not discuss any potential complications with the process, which have been documented when conventional PSA testing occurs, including patients and clinicians typically not first having a balanced discussion of the risks and benefits of PSA testing as a cancer screening tool.

The "greatest potential" for the new in-office test may be for patients who are undergoing active surveillance for low-risk prostate cancer, say the Johns Hopkins urologists.

"These patients require frequent PSA level testing and concerns exist regarding patient compliance," they write.

The test is likely to decrease the inconvenience of serial PSA testing and "might possibly improve patient adherence to active surveillance protocols," say Meyer and Gorin.

However, the pair acknowledge that new test is currently restricted to prostate cancer screening.

For that reason, Marshall University's Wyner envisions limited use in the urology setting at first.

"In my practice, I would most likely use the test in a patient who does not have a primary care provider, who comes for an annual 'prostate check' or for an unrelated problem, such as erectile dysfunction," he told Medscape Medical News.

Despite the FDA approval, the new test still has barriers to getting into clinical practice. The federal government regulates lab testing via the Clinical Laboratory Improvement Amendments (CLIA).

That comes with some regulation, observed Wyner.

"This new point-of-care test will find a market; however, I suspect that many physicians will not want to deal with its associated CLIA regulations!" he wrote in an email.

However, Meyer and Gorin point out that, under CLIA, certain lab tests are "simple laboratory examinations and procedures that have an insignificant risk of an erroneous result" and are thus categorized as "waived." Examples include urine dipsticks and fingersticks for blood glucose. The FDA, which makes this determination, has not yet announced if the Sangia Total PSA will get a CLIA waiver or not. The waiver would facilitate clinical uptake, they suggest.

Primary care is the more likely destination for the new test, suggested urologist Wyner.

"My patients who have PCPs generally get all of their yearly labs, including their PSA, at either the PCP's office or at an outside laboratory," he said.

In that setting, caution should be exercised, says Cara Litvin, MD, an internist at the Medical University of South Carolina, Charleston, who has studied PSA decision-making.

"While this new test makes it easier and quicker for men to obtain PSA test results, it's important to remember that not all men should be routinely screened for prostate cancer," Litvin told Medscape Medical News in an email.

For men ages 55 to 69, both the United States Preventive Services Task Force and the American Urological Association recommend that men have an opportunity to discuss the potential harms and benefits with their physician before deciding to undergo PSA testing, she said. The test is not recommended for routine use in men 70 years and older.

Meyer, Gorin, Wyner, and Litvin have disclosed no relevant financial relationships.

Nature Reviews Urology. Published online April 4, 2019. Abstract

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