Quest Diagnostics (DGX) and LabCorp (LH) are engaged in a fierce battle to meet the sudden spike in demand of high-volume molecular diagnostic and antibody testing sparked by the coronavirus pandemic.

As the U.S. ramps up its testing capabilities, labs are being helped by eased supply constraints and more domestic manufacturers producing badly needed kits. The stakes are high, given that mass testing is needed to ease stiff restrictions that have sent the economy reeling.

Amid an outbreak that’s sickened over 800,000 Americans and killed nearly 50,000, the two largest commercial labs in the country have created and are using testing regimens that account for the lion’s share of the U.S.’s nascent testing efforts. The process was facilitated in part by the U.S. Food and Drug Administration, which eased approvals for new testing in late February as the crisis migrated from Asia across the world.

Private labs have become an integral part of the COVID-19 rapid response team. According to the American Clinical Laboratories Association, all commercial labs — including Quest and LabCorp— have completed 2.5 million tests, half of the 4.1 million performed nationally.

On Tuesday, the FDA approved LabCorp’s at-home coronavirus testing, the first of its kind. The nasal swab test will first be provided to first responders and frontline health workers, but will soon be commercially available — for $100 plus shipping.

Dr. Brian Caveney, chief medical officer at LabCorp, told Yahoo Finance the company has been able to escalate its capabilities, despite a strained supply chain that had created a hefty testing backlog.

“Often, some of the problem has been on the front end, whether it has been a shortage of the actual swab, and specific solution needed to protect the swabs, or just people’s ability to go to a health care provider who is able to collect the swabs, given that so many physicians offices across the country are closed and are doing telehealth only,” he said.

Sometimes, it was also more tests being submitted for processing than the company could process at a time based on its current instruments.

Dr. Jay Wohlgemuth, chief medical officer at Quest, told Yahoo Finance in a recent phone interview that the company has been able to add more instruments as the have been approved by the FDA. The lab giant is also looking into providing at-home testing, which they also do for other wellness tests.

Quest is also looking to create a blueprint for businesses looking to reopen, by collecting best practices from its own work sites as well as other employers.On an earnings call Wednesday, company executives said they are working with employers to offer antibody tests or rapid on-site testing, and are mulling creating corporate screening events, such as those that currently exist for the flu.

As the two giants make headway in their weekly capacity for COVID-19 testing, they are also both working on ramping up antibody testing as more states look to restart their battered economies.

Just this week, Quest began offering Abbott and Euroimmun antibody tests — which are both authorized by the FDA. Meanwhile, LabCorp announced its expansion of antibody tests, and expects to be able to detect the virus in asymptomatic individuals.

To date, regulators have approved four antibody tests, though there are a number of other self-validated tests flooding the market that will eventually need to be authorized by the FDA and validated by the Centers for Disease Control.

But there are questions about whether or not antibody tests will be reimbursed in the same way other lab work is — i.e. by insurers — and at what rate. Quest’s Wohlgemuth said those details have not been finalized, but the discussions are ongoing.

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Anjalee Khemlani is a reporter at Yahoo Finance. Follow her on Twitter: @AnjKhem

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