Every year Inc. Magazine publishes a list of the fastest growing private companies in the United States. While the publication's method has its drawbacks, the resulting list is much more concrete than many of the subjective lists of top companies, apps, or products floating around. Inc. ranks companies by percent growth in revenue over the course of the past few years. What's more Inc. publishes the percent growth figure for the three-year period along with total revenues that the company raked in for 2011. Rare data for private companies to disclose.

To qualify, companies need at least $100,000 in revenues for the first year (in this case it was 2008) and at least $2 million in revenues by 2011. Since the 5,000 companies are ranked by percent growth in revenue, those that have a smaller revenue figure to start with are more likely to make the list, but, as noted above, it's a better method than most.

This year I noticed a handful of digital health companies found their way into the top 5,000. At least a couple of these should be familiar:

Vitals.com ranked 47th overall and took third among health-related companies on Inc.'s list. The New Jersey-based company grew its revenue an impressive 4,637 percent between 2008 and 2011. According to Inc., Vitals had annual revenues of $6.4 million in 2011. Vitals offers online doctor ratings as well as the ability to book appointments with some doctors online -- MobiHealthNews recently mentioned Vitals deal with Aetna to power the health plan's ratings in its popular iTriage app.

iSirona took 82nd spot overall and fifth among health-related companies on the list. The Florida-based company grew revenues 3,359 percent between 2008 and 2011 with total revenues for 2011 at $6.7 million. iSirona offers medical device connectivity for networked and un-network medical devices in hospitals to transmit data into the facility's EMR. Part of the company's pitch is "true wireless mobility" without expensive hardware.

GlobalMed snagged the 95th spot overall and seventh among health-related companies on Inc's 5000. GlobalMed grew revenues by 3,094 percent during the review period and brought in revenues of $26.3 million in 2011 -- making it the biggest company by revenue on this roundup of digital health companies. GlobalMed offers a wide range of telemedicine devices and systems, including cameras, peripherals, and scopes as well as software for medical imaging digitization and store-and-forward.

Patient Conversation Media came in at number 162 overall and 12th among health-related companies. The company reported a 2,059 percent increase in revenue during the review period and $2.4 million in revenue for 2011. Patient Conversation Media describes itself as "a technology media enterprise focused on the digital evolution within the health industry." It offers original content to patients through their own care providers, including physicians and pharmacists. The company also owns a handful of consumer health brands and websites, including dailyRx, RxWiki, 1-800-Oncologist and 1-800-Therapist.

Forward Health ranked 337th overall and 27th among health-related companies that made the list. The New York-based media company grew its revenues 1,127 percent between 2008 and 2011 and it reported total 2011 revenues as $5.2 million. Forward Health is a health media company that runs a number of consumer health websites targeted at various groups or specific to particular health conditions. The company makes money by selling advertisements to (mostly pharmaceutical) companies interested in reaching those audiences. Their sites include: Men's Health Base, Women's Health Base, Pregnancy Girl, Diabetes Dial, Cold and Flus, and Clear Mental Health among others.

While Inc's list is not comprehensive -- only companies that apply and are willing to disclose revenues have a chance at being included, of course. It is, however, worth keeping tabs on. Curious to see how many more digital health companies make the list in the next few years.

Five out of 5,000 is a fairly low benchmark. I'd wager that percent growth in four years time will be impressive.