Did you know? Tampa Bay has 73 of the 5,000 fastest-growing companies in the nation

A 37-employee specialized toxicology lab that provides drug testing of urine enjoyed a 4,415 percent growth rate in revenues for the past three years, making Physicians Toxicology Laboratory the fastest-growing private company in the Tampa Bay area.

The company also ranks No. 59 nationwide on the just unveiled Inc. 5000 list for 2015 — which lists the fastest-growing businesses in the country.

Physicians Toxicology Laboratory, based on Johns Road east of the Veterans Expressway, says its service helps protect physicians who prescribe drugs that could potentially be abused.

It's apparently a business in high demand.

Other top 10 companies to make the Tampa Bay list include No. 2 E-Telequote, whose 80 employees help market Medicare health insurance coverage on behalf of insurance companies; and No. 3 Nitro Mobile Solutions, a mobile app software developer that added 24 of its 26 employees in recent years.

Not all of the top 10 are health care or tech firms. At No. 8, Cabinets.com with 19 employees is an online retailer of wooden, partially customized, discount kitchen cabinets.

The annual Inc. 5000 rankings are a serious reminder of the depth and audacity of private business startups in the Tampa Bay area and the United States. In addition to astonishing growth rates that this year topped 100,000 percent in some cases, the rankings remind us of the relatively invisible small-business markets in the metro area and across the country that provide constant innovation and jobs.

In all, 73 of the 5,000 fastest-growing U.S. companies of the Inc. 5000 call Tampa Bay home. Some of the names may be more familiar to readers than the top 10, which tend to be smaller firms that find it easier to generate such enormous growth rates. Lower on the Inc. 5000 rankings here, though, are firms such as 21-employee Alakai Defense Systems in Largo (No. 2,246), online travel insurance provider Squaremouth in St. Petersburg (No. 2,703), the larger 180-employee Vology in Oldsmar (No. 2,963) and Tampa's well-publicized College Hunks Hauling Junk & Moving (No. 3,389).

Last among locals listed on the Inc. 5000 at No. 4,946 is Palm Harbor retailer the Spice & Tea Exchange, which has 14 employees and a three-year growth rate of 45 percent.

Nationwide, the No. 1 firm for growth this year is Ultra Mobile of Costa Mesa, Calif., with a three-year growth rate of 100,849 percent to $118.2 million in the telecommunications industry.

This year's Inc. 500 (the top 10 percent of the Inc. 5000) achieved a median growth rate of 1,772 percent. Three of Tampa Bay's fastest-growing firms topped that number.

Past Inc. 500 top-gainers in the Tampa Bay market include Tampa's LabTech Software, which notched a 5,208 percent growth rate, and St. Petersburg defense contractor Crystal Clear Technologies, which grew 16,000 percent.