CLN - Focus on Molecular Diagnostics

Implementing Molecular Testing for Gastrointestinal Infections in Clinical Practice

An interview with Nathan A. Ledeboer, PhD

Jen A. Miller

A man placing his hands over his stomach

Molecular diagnostic technologies have revolutionized testing for gastrointestinal infections in many areas of clinical practice. But it hasn’t entirely kicked other kinds of diagnostics off the field—at least not yet.

We spoke to Nathan A. Ledeboer, PhD, professor of pathology at the Medical College of Wisconsin and associate chief medical laboratory officer for Froedtert and the Medical College of Wisconsin, about the role of molecular testing in this area today, figuring out the reimbursement piece of the puzzle, and what the future might hold.

What are the most common gastrointestinal infections affecting patients under your care?

Let’s break this down into those patients who have had gastrointestinal-related illness in the U.S. and those who may have traveled. We tend to see both.

Among those that acquire it in the U.S., there’s community-acquired and healthcare-acquired gastrointestinal illnesses. The two most important things that we deal with in the area of healthcare-acquired infections are C. difficile and norovirus.

When we think about community-acquired pathogens, the most common we see are those you would expect: Salmonella, Shigella, Shiga toxin-producing E. coli, and Campylobacter. We also see a fair amount of community-acquired norovirus, but we don’t test for that frequently.

With travelers, it will depend upon where they have been. If they’ve traveled to a developing nation, we most commonly see traveler’s diarrhea, which is usually Enterotoxigenic E. coli.

What are the advantages of using molecular tests for detection of gastrointestinal pathogens?

There are two really significant advantages. First and foremost is the turnaround time. We’ve moved gastrointestinal pathogen testing from a rather passive process under culture with turnaround times of two to three days to getting results in as little as two to three hours with molecular testing.

It’s also improved sensitivity. For example, with Shiga-toxin producing E. coli, we see differences of sensitivity of 50% or greater. With Campylobacter, Salmonella and Shigella, that improvement can be from 10% up to 30–40%.

There’s also a third advantage I see. It’s increasingly more difficult to find staff in the clinical laboratory. Being able to perform these tests with a molecular approach helps. Working up lots of negative stool cultures is generally not something people want to do in the laboratory, and it also takes a lot of time. So, addressing this with a more straightforward approach to testing can help with staffing challenges as well.

What have you learned since implementing molecular testing for gastrointestinal infections in routine practice?

We’ve talked about the improvements in sensitivity, and we’ve talked about the improvements in turnaround times—both very impactful for patient care. However, we’re still facing a reimbursement picture that has become significantly more challenging.

When many of these molecular tests emerged, in most cases we were able to get paid for what we tested. Today that is certainly not the case, and it will vary depending on where you are in the country. Developing a reimbursement strategy and ensuring that your payers buy into that is incredibly important.

Along the lines of reimbursement, with a test that is primarily run in the ambulatory environment, laboratories also need to take into consideration the patients’ cost. In areas where you have many patients who may be on a high deductible healthcare plan, depending on the size of the panel you are running, that patient may be facing a bill ranging from $100 to $500 to even $800. Patients push back significantly when they get a large bill from their healthcare center. The pushback comes to places like primary care offices and urgent care providers. Then they push back on the laboratory test menu.

I believe laboratories need to develop a high level of understanding of how reimbursement works in their markets. Really doing what you can to address costs for patients and the healthcare system while also performing testing at a high level of quality is important. Balancing those is a huge challenge.

Are there specific patient populations that see most benefit from molecular diagnostic testing?

Everybody benefits from a better turnaround time. Everybody benefits from a higher degree of sensitivity.

One of the groups which I believe has really experienced a great deal of advantage are immunocompromised patients, who come in with a couple of days of diarrhea. The clinical team is really trying to determine whether it is infectious or if there is another underlying condition or cause. If our clinical partners can quickly rule out an infection, that helps them a great deal.

Do you think that molecular testing will replace more traditional methods like culture and microscopy in the near future?

I don’t think that they’ll entirely replace culture and microscopy, but I think it will change the order.

For gastrointestinal illness, as a screen we’ve already seen a significant shift towards molecular testing. Cost, however, can be and will continue to be important and can be a driving factor in why some health systems, clinics and laboratories continue to choose culture. That’s something we really do have to continue to address. How do we provide this level of testing and make it affordable to patients, so we make it easy to do the right thing?

There will also continue to be value in performing culture for certain scenarios. For example, many daycare facilities and schools will require a negative test if a child has been diagnosed with Shigella. You can’t necessarily do that with molecular tests because we know DNA can hang out in the stool for an extended period.

We continue to need isolates to do good public health, and in order to do good epidemiology and susceptibility testing. Getting isolates is important for that. In the near future, and even intermediate future, we’re going to continue to need culture.

What do you see as the future of molecular testing?

I think we’re going to see a couple of different trends. Costs are coming down as testing becomes more democratized. That’s a good thing. We are also seeing increased adoption.

I believe we will see the biggest advancement in the antibiotic resistance space, and in the future push further and further into next generation sequencing. I think that’s going to be an area where we’re going to see a great deal of development and investment in hospitals.

The other thing that really needs to be considered is whether we can, as a field, get together with our insurers and start to develop guidance around what’s going to be paid regardless of what you test for. It allows us as healthcare providers to focus on what we need to do in the best interest of the patient.

Some of the testing panels will probably change over time. For example, for an immunocompromised patient, the clinician will want to be a bit broader in workup of this patient. For patients with travel or exposure to an environmental source where parasites would be in the differential, molecular testing for the appropriate array of parasites could be selected by the provider.

With a healthy adult, maybe we are only interested in the big four, versus an elderly patient in a nursing home where we’re concerned about the spread of norovirus. If we can start to think about reimbursement a bit differently, we can then start to think about what we test for in the context of the patient. Instead of developing panels based on what we can and can’t get paid for, we can instead build panels for patients’ underlying disease state and what is needed for patient care.

Jen A. Miller is a freelance journalist who lives in Audubon, New Jersey. +Twitter: @byJenAMiller

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