During a recent conference call with other pharmaceutical industry executives and Reuters, Roche (OTC: RHHBY) CEO Severin Schwan warned about a lack of coronavirus testing capacity. Last week, Roche began shipping 400,000 COVID-19 tests to hospitals and laboratories across the U.S., and is prepared to continue doing so at a pace of 400,000 per week. Roche isn't the only major test manufacturer either. Earlier this week, Thermo Fisher Scientific (NYSE: TMO) said it could produce millions of COVID-19 testing kits as well in the coming weeks. Image source: Getty Images. Limited capacity to produce results Despite the rapid ramp-up in production of those testing kits, Schwan still firmly recommends that only high-risk patients and those showing COVID-19 symptoms should use them. That's because manufacturing millions of test kits is a lot easier than producing millions of results. For example, the models of laboratory equipment that run Roche's COVID-19 test -- its cobas 6800 and cobas 8800 Systems -- can produce 384 and 960 results in an eight-hour shift, respectively. And while those devices are fully automated, making them are incredibly efficient, a flood of tests from well-meaning low-to-moderate risk patients could significantly lengthen turnaround times on diagnoses for everyone. Here's where the bottleneck could occur: As Roche noted in a press release issued last week, "Our global install base for the cobas 6800 and 8800 Systems is 695 and 132 respectively." Only 110 of those are in the U.S., the company told Bloomberg this week (and it declined to say what proportion were the newer, faster 8800s). That means that the volume of U.S. tests that can be processed on those machines will be at best in the low hundreds of thousands each day. Regardless of how many test kits get made available, there's only so much processing capacity. In addition to a limited number of machines, the world could also be facing a shortage of the reagents used to run coronavirus tests. Recently Qiagen, a major manufacturer of testing reagents, announced plans to boost production to support more than 20 million tests per month by the end of the year. In the meantime, the FDA revised the emergency use authorization submission guidelines to reflect a shortage of the reagents required to process coronavirus test kits. Instead of running 50 samples as recommended previously, the FDA now suggests manufacturers include data from just 30 contrived clinical specimens. 10 stocks we like better than Roche Holding Ltd. (ADR)When investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and Roche Holding Ltd. (ADR) wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of March 18, 2020 Cory Renauer has no position in any of the stocks mentioned. The Motley Fool recommends Qiagen N.V. The Motley Fool has a disclosure policy.Source