In Production: Quick and Cheap Bedside Test for Cortisol Uses Smartphone

An innovative method of measuring the stress hormone cortisol is being developed by researchers in Utah. Requiring just a simple kit and a smartphone to read results, this new approach should allow quick, affordable, and accurate testing of cortisol levels, enabling rapid diagnosis of adrenal diseases, the investigators say.

“A lab charges about $25 to $50 for a quantitative salivary cortisol test and has a turnaround time of days to a week,” said lead researcher Joel Ehrenkranz, MD, director of diabetes and endocrinology at Intermountain Medical Center, Murray, Utah. “This test, taken in a medical office or at home, will cost less than $5 and take less than 10 minutes,” he noted.

Dr. Ehrenkranz reported the details of the new test kit, developed at his institution, at ICE/ENDO 2014 week. He said he and his fellow researchers are now collating clinical data for a Food and Drug Administration (FDA) submission and hope to gain approval of the test as a class 2 medical device in the United States in 2015.

Chair of the session, Jeremy Tomlinson, MD, of University of Birmingham, United Kingdom, said the new approach employs “great technology and is an interesting innovation, but there are a few concerns. For example, how well will it perform against the state-of-the-art technique for measuring salivary cortisol, which is mass spectrometry — is it as sensitive?”

Also there is a possibility the immunoassay in the new test will cross react with another steroid hormone, prednisolone, that people might be taking for a whole range of inflammatory conditions, so “you would want to make sure it’s measuring what you want it to,” he noted.

And finally, there is the question of exactly how this would be used.

Cortisol levels are needed when conditions are suspected where too much or too little cortisol is produced, but the diagnosis for most of these doesn’t really need to be immediate, Dr. Tomlinson explained to Medscape Medical News. However, he conceded there might be a role for the assay in patients presenting to the emergency room or in developing nations.

No More Presumptive Treatment of Adrenal Insufficiency

At the meeting, Dr. Ehrenkranz said that adrenal diseases are commonly overlooked because current methods of measuring salivary cortisol require instrumentation and technical personnel and so are costly and unable to deliver timely results.

He noted also that a stint in the developing world convinced him that a simpler test was needed, so he and his colleagues set about developing an assay that would be inexpensive and easy to perform — they came up with disposable cortisol immunoassay strips containing a glass fiber element with colloidal gold-labeled murine anticortisol antibodies and a saliva collection pad.

The person being tested inserts a strawlike saliva collector under the tongue, which wicks the saliva to the immunoassay test strip housed in a cassette, which is then inserted into a reader in the device.

“The device…includes a case, a light pipe, and a lens and costs about a dollar to make. There is no battery power, and it’s unbreakable, passive, and reusable,” Dr Ehrenkranz said.

Because of the physical properties of the gold nanoparticles, a smartphone flash can illuminate and camera-image the color generated by the colloidal gold-labeled anticortisol antibodies, he explained.

The color subsequently generated is “read” by an app on the smartphone to give a cortisol reading, based on an algorithm derived from observed vs reference salivary cortisol values. The R value of this curve was 0.996 for salivary cortisol in the range of 0.012-3.0 µg/dL, Dr Ehrenkranz noted.

The new technology can therefore measure cortisol in a range sufficient to diagnose adrenal insufficiency and hypercortisolism and monitor physiologic variations in cortisol concentration, he said.

And the software is “operating-system agnostic,” he added, meaning the device can be used on all platforms, including iOS, Android, Windows, and BlackBerry, and it has a universal form factor that works with all smartphones.

“Measuring salivary cortisol at the point of care in 5 minutes using an inexpensive immunochromatographic assay, reader, and smartphone may obviate the need to presumptively treat patients for adrenal insufficiency and makes cortisol assays available to regions of the world that currently lack access to this diagnostic test,” he concluded.

Test of Use in Emergency Room, in Developing Countries

Dr. Tomlinson explained that diagnosis of Cushing’s syndrome — caused either by tumors of the pituitary gland producing too much ACTH or tumors of the adrenal gland producing too much cortisol — or alternatively, diagnosis of conditions where it’s thought too little cortisol is being secreted, such as Addison’s disease — an autoimmune process whereby the adrenal gland is destroyed — are not conditions “you necessarily have to diagnose in a few minutes by the bedside,” and therefore it is better to use the “gold standard” of diagnosis, mass spectrometry, in these cases.

But the new test “might be of use in determining whether people have enough of their own natural corticosteroid, in terms of deciding whether you need to give supplemental cortisol to people in an emergency situation,” he explained.

This could include patients presenting with suspected or underlying pituitary or adrenal disease or in people who have been on large doses of steroids who have then stopped taking them, so there will be a resulting suppression of their natural steroid production, he noted.

“That’s not an uncommon situation that we see in the emergency room. At the moment, if there’s suspicion, we might take a test but it takes a day or 2 to come back from the laboratory, and in the meantime we will give patients [presumptive] steroids. But you could do this test by the bedside,” he acknowledged.

And in developing countries, use of this test “is feasible, where cost comes into the equation and you might not have access to mass spectrometry; this could be an alternative and would help you to exclude or make these diagnoses,” he concluded.

This study was privately funded. Dr. Ehrenkranz and colleagues report no relevant financial relationships.

Joint Meeting of the International Society of Endocrinology and the Endocrine Society: ICE/ENDO 2014; June 24, 2014. Abstract OR48-2

From http://www.medscape.com/viewarticle/827580

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