Shareholders of Fulgent Genetics (NASDAQ: FLGT) have been on quite a ride over the past year. The diagnostics company has subjected investors to both euphoria and despair. COVID-19 ushered in an era of testing that propelled shares to huge gains, and the authorization of vaccines convinced Wall Street the boom was behind us. The numbers looking back have been amazing, but there's one estimate that should give shareholders a lot of optimism about the company's future. Image source: Getty Images. Fulgent's growth is off the charts As the pandemic took hold and SARS-CoV-2 began to spread, the genetic testing company sprang into action. By mid-May 2020, the company had received authorization from the U.S. Food and Drug Administration (FDA) for its COVID-19 molecular test. The subsequent volume dwarfed everything the company had ever done and revenue followed. Period Billable Tests YOY Test Growth Revenue YOY Revenue Growth Q1 2020 13,163 75% $7.8 million 44% Q2 2020 180,513 1,003% $17.3 million 105% Q3 2020 1.04 million 4,800% $101.7 million 880% Q4 2020 3.2 million 23,000% $295.0 million 3,400% Data Source: Fulgent Genetics. YOY = year over year. That's not to say the entire business was growing. The company said its core testing business grew in January and February of last year, but volume dropped off as most non-COVID healthcare services were delayed. COVID testing more than made up for the loss. Surprisingly, the non-COVID segment wasn't down for long. The core business is strong The arc of non-COVID testing volume in 2020 tells a clear story of resilience about the business. Going further, comparing Fulgent's numbers to genetic testing rival Invitae (NYSE: NVTA) provides a good sense of how well the business performed relative to the industry -- and how 2021 is shaping up. In the first quarter of 2020, before COVID disrupted the traditional testing operations, both companies were growing quickly. Fulgent reported 75% volume growth while Invitae posted 64%. In the second quarter, both felt the impact. Fulgent's testing volume was flat compared to the first quarter, but Invitae's fell 22%. As the virus waned and some geographies began opening up, both saw a rebound in the third quarter. Billable tests for Fulgent and Invitae were up 57% and 42%, respectively, compared to the prior quarter. For the final quarter of 2020, pent-up demand propelled each to robust year-over-year growth -- 43% for Fulgent and 61% for Invitae. Those are impressive numbers, but there is one that's even more impressive for shareholders of Fulgent Genetics. More fuel for growth Both companies provided guidance for 2021 that show continued expansion. Invitae projects revenue will grow 62% this year to $450 million. However, Fulgent was able to add a little extra fuel to the fire. Management's estimate of $70 million in revenue for the next-gen sequencing business is 92% more than 2020. That growth could be the most important number for shareholders to pay attention to. The performance is the result of both a fast-growing industry, as well as the company's contract to conduct virus surveillance testing for the U.S. Centers for Disease Control and Prevention (CDC). The deal marrying COVID demand with its core genetic testing is proof that Fulgent has not only weathered the storm of 2020 but has come out stronger. Year Genetic Testing Revenue YOY Revenue Growth 2017 $18.7 million 3% 2018 $21.4 million 14% 2019 $32.5 million 52% 2020 $37 million 14% 2021 Guidance $70 million 92% Data Source: Fulgent Genetics. YOY = year over year. Prepared for takeoff Fulgent's quick development of a COVID test demonstrated resilience in its core genetic testing, and the ability to combine the two for new growth opportunities has been spectacular. Management now says it can handle 10,000 genetic tests per day. For context, the company performed a little more than 300 per day during the fourth quarter of 2020. The contract with the CDC isn't the only avenue of new growth. It is also awaiting authorization for a new product that tests for both COVID and influenza and continues to push its at-home testing products. Fulgent also won part of a $2 billion contract with the Department of Homeland Security for COVID testing that it has yet to include in its guidance. For investors worried about the sustainability of COVID testing, Fulgent Genetics' ability to parlay that demand into new business for its genetic testing should quell some of the fears. Management is showing an ability to innovate for customers that will exist long after COVID testing. That should set the company apart in a fragmented industry and position it as a sought-after partner in 2021 and beyond. 10 stocks we like better than Fulgent Genetics, Inc.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 Fulgent Genetics, Inc. 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 February 24, 2021 Jason Hawthorne has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Fulgent Genetics, Inc. and Invitae. The Motley Fool has a disclosure policy.Source