I work from 8 a.m. to 5:30 p.m. I don't have time to go to the hospital. Here I can just walk in, the 34-year-old teacher's assistant said recently as she waited during her lunch break for a test.

I have kids to support. I can't afford to take a day off from work.

Santiago is one of some 3,000 people each year who visit the Family Van for free checks of their blood pressure, blood sugar and cholesterol level.

The nonprofit clinic affiliated with Harvard University provides simple tests that can give an early warning of an impending health problem or help manage an existing condition, such as diabetes.

The van -- which visits six low-income neighborhoods around Boston weekly -- is one of about 2,000 such mobile clinics in the United States. Advocates say the approach can help control the rising cost of health care by helping people with chronic diseases to stay out of the emergency room, often the first recourse for inner-city residents.

Our medical system in this country is focused on illness. What we are doing is helping people when they're sick, said Jennifer Bennet, executive director of the Family Van, which is backed by Harvard Medical School.

It would be a lot less expensive and people's quality of life would be vastly improved if we as a society and as a country start to look at addressing these problems long before they get to that acute stage.

The United States spends some $2.5 trillion on health care each year. That works out to about 15 percent of gross domestic product, considerably higher than any other developed economy, according to a Kaiser Family Foundation analysis.

GROWING NUMBERS

A growing number of clinics like the Family Van operate in the United States, according to the Mobile Health Clinics Network, which has been tracking clinic numbers for six years and finds more each time it conducts its informal census.

There is no doubt about it, it's growing, said Darien DeLorenzo, executive director of the San Francisco-based group.

The mobile clinics are largely nonprofit and most provide general medical care, though smaller numbers specialize in dentistry or mammography.

Many urban clinics keep budgets tight by relying on healthcare educators and students as staff, referring patients to doctors or hospitals when more is needed. Their rural counterparts more frequently have doctors and nurses on board, to serve communities without health care facilities.

The Family Van estimates that every dollar it spends on its operations pays off $36 in economic benefits, including the effect of averting nonemergency visits to hospital emergency rooms and the value of the tests it provides.

The average visit to the Family Van costs $117, versus $923 for a nonemergency visit to a hospital emergency room, according to an analysis by the clinic, Harvard Medical School and other experts.

These programs can also help push the nation's overall medical tab down by alerting people to nascent health problems before they become critical, advocates said.

SERVING THE UNDERSERVED

When you're serving the underserved, healthcare is a luxury, said Kathy Ficco, executive director of community health at the St. Joseph Mobile Health Clinic in Rohnert Park, California, which operates a similar clinic.

Their main focus is food and shelter ... It's not until a problem creates pain or suffering that they will seek care.

A visit to the Family Van can take as little as seven minutes, though staffers will spend as much as 45 minutes with people who have questions about their conditions.

Going to the hospital takes a long time, said Badshah Rahman, 38, who stopped in on an August afternoon for a regular blood pressure check. This is really easy.

Many of the Family Van's patients are regular visitors who drop in every few weeks. That level of frequency may be the clinics' greatest benefit.

What you need there is ongoing monitoring of folks with chronic conditions and to the extent they don't have that kind of ongoing monitoring in the traditional health care system, the van fills in that gap ... that's terrific, said Michael Sparer, chair of the department of health policy and management at Columbia University's Mailman School of Public Health.

Still, he noted, clinics staffed by educators cannot provide the same level of care as a visit to a doctor.

They are a stopgap solution, Sparer said.

Even in Massachusetts, where a law passed in 2006 requires almost every resident to have health insurance, many inner-city residents turn to hospital emergency rooms first.

This is a problem that may play out across the United States in the wake of the healthcare reform law, which aims to extend health insurance to 32 million uninsured Americans.

Everybody has a doctor on paper but they can't get in, the Family Van's Bennet said. The number of doctors hasn't changed, just the number of people who have insurance.

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