Bob Underwood, MD (Host): Biliary atresia is a rare condition that affects newborn babies and can quickly progress to liver failure. Symptoms can be subtle and easy to miss, which makes detection challenging and sometimes time consuming. To combat these issues, Hepatologists and Gastroenterologists at Children's Health have developed a new diagnostic blood test called MMP-7 to speed up the diagnostic process without sacrificing accuracy.

Children's Health is currently the only health system to offer this blood test and has made it available to physicians nationwide. This is Pediatric Insights, Advances and Innovations with Children's Health, where we explore the latest in pediatric care and research. I'm your host, Dr. Bob Underwood, and today we have with us Dr. Sindhu Pandurangi, Pediatric Gastroenterologist at Children's Health and Assistant Professor at UT Southwestern. And she's here to discuss how MMP-7 is being used to accurately diagnose biliary atresia. Welcome, Dr. Pandurangi. Thank you so much for being with us today.

Sindhu Pandurangi, MD: Oh, thank you. I'm glad to be here.

Host: Yeah, so some really great research that you're doing. Can you share with us the typical symptoms of biliary atresia and why is it so challenging to diagnose?

Sindhu Pandurangi, MD: In general, I'd like to just start off by talking about neonatal cholestasis, which is a diagnosis that pediatricians definitely see in general practice, as well as in our subspecialty of pediatric gastroenterology and hepatology. Neonatal cholestasis, meaning an elevated direct bilirubin, occurs in about one in every 2500 infants, and the underlying cause of neonatal cholestasis has a very broad differential.

So we're thinking about things like genetic causes, infections, metabolic causes, sometimes prematurity can play a role, and then anatomic causes can also cause a neonatal cholestasis. And when we're seeing a patient with neonatal cholestasis, the main question in our minds is if this could be biliary atresia.

So biliary atresia is a congenital disorder of the development of the bile ducts so that bile can't effectively drain from the liver and over time can lead to scarring and cirrhosis. And, biliary atresia overall is a pretty rare disease. It's actually more common in Asia with an incidence of about one in every 6,000 in Taiwan.

And in the United States, some recent estimates are about one in every 12,000 live births. But actually overall, biliary atresia is the number one indication for pediatric liver transplant worldwide.

Currently the gold standard in care for biliary atresia is to try to make this diagnosis as quickly as possible and get these babies to a surgical center where they can have a surgery called the Kasai Hepatoportoenterostomy.

It really rolls off the tongue. The Kasai surgery is essentially where those atretic extrahepatic bile ducts are removed and a portion of the small intestine is brought up to the liver and it allows the liver to drain the bile. And what we know about the surgery is that the earlier it's done, the better the outcome.

So some studies suggest, doing this surgery, before 60 days of life. Others suggest doing it even earlier, less than 45 days of life. So you can kind of get a sense here of maybe the urgency of making this diagnosis. To make things even more difficult, biliary atresia can present just like other causes of neonatal cholestasis, like that big laundry list that I gave you earlier. So that has really been the impetus and the rush to find better ways to diagnose it.

Host: So what was the more traditional way of diagnosing it, or what is currently?

Sindhu Pandurangi, MD: Traditional ways making the diagnosis of biliary atresia, would be standard labs that many are already familiar with, with our liver biochemistries. So, looking at fractionated bilirubin, looking at GGT levels, looking at ultrasound and the presence of a gallbladder on ultrasound or any other characteristic radiologic features.

HIDA scans have also been used, and then also liver biopsy, has been commonly used to look for presence of extrahepatic biliary obstruction. But that's pretty invasive, for a baby. It's a lot of steps. It's a lot and it can get really convoluted and all the while you're wondering, could this baby have another type of cholestasis that's not biliary atresia? And also, oh man, if it is biliary atresia, I better be making this diagnosis quickly.

Host: Right. So what is the MMP-7 test? And can you speak to the international collaboration that it really took to bring it to fruition?

Sindhu Pandurangi, MD: So, MMP-7, so that stands for matrix metalloproteinase-7, and that's an enzyme that is actually found in many different parts of the body. It's involved in the breakdown of extracellular matrix, so it's involved in tissue reparation processes and an extracellular matrix degradation.

And so we know that in the biliary system, it's released on epithelial injury in the cholangiocytes, so in the bile duct cells. And so that's kind of been the experimental phenotype that we've seen with MMP-7. So, in terms of the work that preceded my recent publication, there's been volumes, and so I just want to highlight all that's been done, but in brief, I'll highlight that, Dr. Beze has group published a paper in 2017, in Science and Translational Medicine. And that was kind of the initial discovery study of MMP-7 as a biomarker of biliary atresia. So they looked at a cohort of 175 infants with BA, and they also compared to healthy controls. And from that study, they were able to distinguish MMP-7 as a strong biomarker to identify biliary atresia.

And then in the following year, in 2018, another paper from his group, published in Hepatology Communications looked at a cohort of infants in China, in Wuhan, China, 135, babies with biliary atresia and 54 healthy controls. And that study looked at how do we actually identify a cutoff on an established assay.

So in that study, they identified that the cutoff of 52.8 on the ELISA based assay, had a very high positive and negative predictive value for identifying biliary atresia from other causes of neonatal cholestasis. And then there have been internationally, many different studies evaluating what is this cutoff point.

How do we know? So we send this test, but what do we make of the results? How do we know if this is significant enough or concerning enough for biliary atresia? And the main issue that we were running into as, you know, I think as a community in pediatric hepatology, all these studies were being done in, China, Japan, Europe, and different cut offs were being identified to make the diagnosis.

And also, different assays too. So that kind of set the foundation for my paper.

Host: Wow. So you've made reference to your paper that was in Hepatology. Is there anything specific you'd like to share about the published results from that paper?

Sindhu Pandurangi, MD: My paper is entitled Diagnostic Accuracy of Serum Matrix Metalloproteinase-7 in a Large North American Cohort. I was fortunate to recently have that accepted for publication in Hepatology, and it's available to be read published ahead of print, currently. So, my study looked at a group of 399 infants with cholestasis who are actually part of a larger NIH NIDDK collaborative called the Childhood Liver Disease Research Network, and I also just want to mention that the prior studies as well, have also studied patients as part of this network.

So, the Childhood Liver Disease Research Network has really been integral in moving this area of research forward in our understanding and utilization of MMP-7. So my study looked at the 399 infants. We had about 201 with biliary atresia and 198 with non-BA cholestasis. So the other types.

And we looked at the diagnostic accuracy of MMP-7 and specifically we wanted to identify a cutoff to make the diagnosis. And we looked at two different available assays for MMP-7. One was an antibody bead based assay. And the other one was a time resolved fluorescence energy transfer assay, so the FRET assay.

And what I'd like to highlight is that overall we found that MMP-7 had a very good discriminative ability to differentiate BA from other types of cholestasis. So our overall AUC, was 0.9. On the antibody bead based assay, we identified a cutoff of 52.8, which was consistent with previous studies, and that cutoff gave us a sensitivity of 94%, a specificity of 78%, a positive predictive value of 65%, and a negative predictive value of almost 97%.

Similarly, we looked at the FRET assay, the fluorescence energy transfer assay, and we found similar discriminative capabilities, but the cutoff was different. The cutoff was lower at 18.2. So overall, I think the takeaway here is that MMP-7 does have a pretty good capability to differentiate biliary atresia from other causes of neonatal cholestasis, and specifically it has a really high negative predictive value.

So, if an infant coming with neonatal cholestasis has a low MMP-7, we can have a pretty good reassurance that they don't have biliary atresia. Now, I think this doesn't override people's clinical judgment. And I definitely advocate for that, especially as we're learning more about this test and using it in the real world.

But I think these are some pretty promising results. And I think the other takeaway is that when physicians are sending this test, they should look to see what assay it was run on, because that will change what cutoff is needed to make the diagnosis.

Host: Yeah, and in the introduction, I talked about this test being available to physicians nationwide. And then you went through the different cutoffs of the results based on the type of assay that was done. So can ordering providers consult with your team in order to interpret those lab results and how would they get in touch with you if they wanted to do that?

Sindhu Pandurangi, MD: So, currently MMP-7 is being run at Children's Medical Dallas. And, anyone who would like to order the test can easily access the requisition online just simply, searching for it. We run the fluorescence energy transfer assay, so the FRET assay, so our cutoff is going to be the lower number, the 18.2. And any questions with interpreting the results, we are more than happy to help anyone who sends this test and needs help with the interpretation and all of that contact information is available on the requisition form. And we chose to use the FRET assay at our institution because we know that we can run the test faster.

And our goal is to have results back to physicians within 48 hours of sending the test.

Host: How do you think MMP-7 will revolutionize the diagnosis for biliary atresia? I mean, does it speed up the diagnostic process and not sacrifice accuracy? What are your impressions?

Sindhu Pandurangi, MD: I think this is the exciting next direction hopefully of this work. Now that I think we have some pretty good evidence to lay the foundation that MMP-7 probably deserves a role in the diagnostic workup of biliary atresia. And moving forward, we have to see in really real world cohorts, see how this could potentially shorten the time to the Kasai hepatoportoentertrostomy for these patients.

I think that by having it be a readily available blood test, this would increase access really to different clinics in different parts of the country, different hospital systems. And the ultimate goal being that we get these answers quickly and we can make clinical decisions faster for these patients.

Host: Absolutely true. And you know, and key for physicians trying to make the diagnosis and for the families of these patients.

Sindhu Pandurangi, MD: Absolutely.

Host: So anything you'd like to conclude with?

Sindhu Pandurangi, MD: I just want to thank you for the time to talk today and kind of talk about my science and I'm very excited for the next steps and to see how we can implement some of these discoveries to improve the care of these patients.

Host: Yeah, it's phenomenal work that you're doing, really, really. Thank you for joining us today and for explaining the work that you've been doing here.

Sindhu Pandurangi, MD: Thank you.

Host: And also, thanks to our audience for listening to Pediatric Insights, Advances and Innovations with Children's Health, where we explore the latest in pediatric care and research.

You can find more information at Childrens.com/GI. And if you found this podcast helpful, please rate and review or share the episode. And please follow Children's Health on your social channels.