In an increasingly convenience-obsessed, time-crunched society, more and more Americans are using home health tests instead of visiting a doctor for a diagnosis.

Do-it-yourself pregnancy tests have been popular since the 1970s, but these days there are approximately 500 at-home tests of all sorts approved by the Food and Drug Administration, according to the agency's Web site — not to mention the vast number of unapproved tests sold primarily online.

Male infertility, colon cancer, menopause and HIV are just some of the conditions that can now be tested for at home, but critics say replacing the M.D. with a kit may be a dangerous trade-off.

Eva Marer, a writer for Health magazine who investigated the tests, said she was surprised by the large number of kits available and their sub-par quality.

"These tests can give you a real false sense of security," she said. "Companies are preying on a vulnerable population … and a fix-it mentality. 'Just do this and you’ll have it taken care of.'"

One Health tester tried First Check Home Screening Test for Colorectal Disease and responded, "I just turned 52 and haven't had a colonoscopy yet. Now that this test was negative I feel I can put it off for another year."

This kind of confidence in home tests is exactly what doctors fear.

"It's a myth that the tests substitute for everything else," said Dr. Richard Roberts, professor of family medicine at the University Wisconsin Medical School, adding that he is concerned about the tests' reliability and the possibility of getting incorrect results.

"I'm aware of instances where people have gone off and committed suicide over a false positive HIV result," he said.

Some conditions are logical candidates for home monitoring however, he said.

"There are certain tests we routinely recommend people do at home, such as glucose and blood pressure," said Roberts. "But some other home tests have often been driven more by companies' eagerness to turn a profit than by any proof they help people."

And the profits are indeed turning. The U.S. at-home test market was $750 million in 1992, according to trade magazine Best's Review, and it was expected to leap to $2.82 billion by the end of 2002.

People who use these tests are typically scared of doctors, don't have health insurance or don't feel they have time to get to a doctor's office, Marer said.

Yet Roberts says these fears are for naught.

"People don't understand sometimes how important privacy is to physicians," he said. "Another perception is that it's more convenient, but I promise you if you come up with a false result you'll be spending a lot more time trying to eventually track down that it was a false result. Would you rather take three half-way tests or one definitive test?"

Home Access, which has been selling an HIV test since 1996, has seen its popularity rise recently, according to company spokesman Kevin Johnson.

The test involves using a "retractable safety lancet " to prick your fingertip and place drops of blood on the specimen card (about the size of a dime) and sending it to the company's lab.

About a week later, testers call to find out the results – a prospect Marer finds frightening.

"This is a bad idea," she said. "You need to be sitting across from a doctor when you find out the results."

But Johnson said this dramatic ending simply doesn't happen. "In the five years we've been operating we've had close to 500,000 tests processed in the lab without one adverse consequence where people freaked out or did harm to themselves," said Johnson.

Callers can either find out their results through an automated system or speak with a professionally trained representative, he explained.

If you do buy a home health test online the FDA suggests being wary if you see that the test "claims to diagnosis more than one illness," is "made in a country other than the United States," or is "made by only one laboratory and sold directly to the public" (which the FDA calls a "home-brew" test not intended for over-the-counter sale).

But even with the numerous FDA-approved tests, Roberts suggests thinking twice about relying on them. He said a key question users should ask is, "What are you going to do with the results?"

"The more effective strategy is to cultivate a good working relationship with your physician," he said. "It's a lot more helpful than trying a test you saw on TV at 2 a.m. or saw in the glossy pages of a magazine."