An angel in the ER: Firm helps patients who can't pay

Overlooking the Chesapeake Bay is a sleepy-looking office tucked inside the first story of a small, sun-bleached building in Bay Ridge.

The business inside the former gas station boasts 120 employees in 11 states from Maine to Florida and as far west as Oklahoma. Though some people are skeptical about the existence of angels, Advanced Patient Advocacy must seem like one to the 30,000 patients who received its help last year.

But it's a very successful angel on a purely earthly plane: APA produced $5.4 million in revenue last year. Inc. magazine named it the 166th-fastest-growing company in the nation, but none of its...