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Model Suggests Sera's PreTRM Test Could Offer Big Cost Savings, Though More Data Needed

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NEW YORK (GenomeWeb) – A recent study suggests that Sera Prognostics' PreTRM test for assessing risk of preterm birth could significantly reduce deaths and costs associated with the condition.

In the study, which was published in the American Journal of Perinatology Reports, researchers at institutions including Ohio State University and Oregon Health and Science University modeled the health outcome and economic effects of the PreTRM test, finding that it could result in a more than 23 percent reduction in infant mortality and annual savings of more than $500 million.

Sera and its collaborators are currently working to launch prospective clinical utility studies that will provide hard data of the sort the AJPR paper aimed to model, said Greg Critchfield, the company's chairman and CEO.

"The goal is to show that by testing and intervening early we can achieve improvements in neonatal health and economic outcomes," he said, noting that Sera is working with insurers in an integrated delivery network setting to design the studies.

The PreTRM test measures two proteins, insulin-like growth factors binding protein 4 (IBP4) and sex-hormone binding globulin (SHBG), to determine a patient's likelihood of preterm delivery. It is intended to be given at 19 weeks gestation and provides women and their doctors with their percent risk of giving preterm birth along with a comparison of their individual risk to that of the general population.

In the AJPR paper, the researchers assumed the test predicted birth before 37 weeks with a sensitivity and specificity of 80 percent, which Critchfield said is around the performance the company has been seeing in its validation studies. In the model, patients identified as at-risk were then treated with vaginal progesterone, with the effectiveness of this treatment assumed to be roughly 20 percent lower than the rate established in clinical trials. The price of the PreTRM test was put at $1,250 in the AJPR model, which Critchfield said was "reasonable."

Using those assumptions, the model determined that in an annual population of 3.5 million births, the rate of spontaneous preterm birth would decrease from 9.8 percent to 9.1 percent, a reduction of 23,430 preterm births; infant mortality would fall 23.5 percent, from 8,300 to 6,343 deaths; and acute conditions at birth would decrease from 11.2 percent to 8.1 percent. In terms of medical costs, these reductions would result in direct medical cost savings of $511.7 million, which, Critchfield noted, accounts only for money saved in the first year of life.

In a separate commentary published in Proceedings in Obstetrics and Gynecology, obstetricians from the Medical University of South Carolina, Christina Care Health System, and Banner Good Samaritan Medical Center, argued the need for biomarker assays like the PreTRM test for identifying patients at risk of preterm delivery.

Scott Sullivan, an MUSC obstetrician and first author on the paper, said the PreTRM test was particularly useful in that it provided positive predictive value, allowing physicians to identify patients likely to give birth prematurely. Existing tests like cervix measurements and fetal fibronectin assays focus on negative predictive value, he said, which allows doctors to rule out patients who are not at risk but doesn't help them identify those patients in need of intervention.

Sullivan has participated in clinical trials for the PreTRM test and uses it in his own practice, which specializes in preterm birth prevention. He said that around 20 percent to 25 percent of the patients in his practice are candidates for the test, though he said in a typical practice this rate would more likely be around 5 percent.

Sera aims to position the test as a general screening tool for all pregnant woman who are not already considered at high risk for preterm delivery. Sullivan said that the field could certainly use a general screening test for preterm birth, but he added that Sera didn't yet have data indicating the PreTRM test would be suitable for this purpose.

"We desperately need a population-wide screen," he said, noting that 70 percent of patients who go into preterm labor have no risk factors. "We miss the vast majority of patients we would like to key in on. The problem is people are not going to [use the PreTRM test for general screening] until a very large trial has been done."

"Screening is a dirty word in obstetrics, because we have been burned and burned and burned with screening tests in the past," Sullivan said. "So, if you are going to screen 4 million people, you have to prove not just that it works, but also that you have an intervention that decreases incidents, saves money, and, of course, lowers morbidity."

"[Sera] has done a large validation study that in my mind shows without a shadow of a doubt that the test is effective, but they have no data on intervention for screening," he said.

The company aims to generate such data via the clinical utility studies it is currently putting together. Sera expects these studies will also help it secure payor coverage, Critchfield said. Sullivan noted that lack of coverage is another factor holding the test back from broader use.

"I anticipate that it will get covered in the next year or two, and then uptake will be more robust," he said. Sera is still in the middle of a limited commercial launch for the test targeted to a select group of customers.

The test's mass spec format also may be a factor that could hinder broad adoption, Sullivan said.

Sera has been a rarity among protein diagnostic firms in that it has committed to bringing its test to market on a mass spec platform. Mass spec has certain advantages over immunoassays including better accuracy and the potential for higher multiplexing, but Sullivan said the fact that doctors must send out the test and then wait a week for results could limit its reach.

"The use of mass spec is a drawback to the test in my view," he said. "If they ever want this to be [for] population-based [screening], and I do, and I know they do, they will have to get it off that platform so that it can be done locally [and] you can get a result in a day rather than a week."

He noted that obstetricians use other tests, such as non-invasive prenatal diagnostics that have to be sent out, but he said ideally the Sera test would be moved to a format that could be done closer to point of care. And, he noted, he was working with the company on efforts looking into developing an immunoassay version of the test.

"I think fetal fibronectin is the model," he said. "We used to have to send it off, but within a couple of years it became point of care."

Critchfield said the company is currently conducting development work on an immunoassay version of the test, but that it still considers mass spec the best platform for the test at this point.

The immunoassay development is primarily funded by the Bill and Melinda Gates Foundation, he said, noting that the aim is to adapt the test to low-cost technologies better suited to underserved areas. One factor making the PreTRM test somewhat amenable to conversion to immunoassay is the fact that it consists of only two proteins.

Critchfield added that Sera continues to see certain advantages to the mass spec format, for instance, its multiplexing capabilities.

"As we discover additional biomarkers, we can incorporate them readily," he said. He noted, as well, that the company sees "several improvements in [mass spec] workflows that would allow the technology to scale massively. We are evaluating these and believe that [mass spec] will be the preferred platform for the time being."