ATLANTA (AP) - Childhood vaccinations and anti-smoking counseling for adults are the most effective preventive medicine, says a new study that ranks medical services based on how many lives they save and how much they cost.

The findings also suggest that some of the best preventive measures - such as colon cancer screening and warning teen-agers about drugs - are reaching surprisingly few Americans.

The study, released Friday, was conducted by the nonprofit Partnership for Prevention and sponsored by the Centers for Disease Control and Prevention. It appears in the July issue of the American Journal of Preventive Medicine.

The study examined 30 examples of preventive medicine, giving each a 1-to-5 rating in two categories - cost-effectiveness and how well it prevents disease or injury.

Vaccinating children for diseases like polio and hepatitis was the only measure with a perfect 10. Anti-smoking counseling for adults and eye exams for the elderly were close behind, ranked extremely effective, with combined scores of 9 each.

The next most effective measures were getting the anti-smoking and anti-drug messages to youngsters. But those measures were also found to reach less than half of their target audience.

"These gaps in care should be closed for the benefit of everyone," said Dr. Jeffrey Koplan, director of the CDC.

Ashley Coffield, an author of the study, said she hopes the findings make health-care providers more accountable for providing services at the top of the list.

Two measures were given the lowest possible scores for both disease prevention and cost-effectiveness - rubella screening for women of childbearing age and tetanus shots for the whole population.

Cholesterol screening, counseling on a balanced diet and regular mammograms for women age 50 to 69 ranked in the middle.

Medical effectiveness was measured by calculating the deaths or injuries that could be delayed or avoided if the preventive service reached its entire target population.

Cost-effectiveness was measured as the cost of a preventive service divided by its medical effectiveness.

In a commentary published in the journal, a physician with the Kaiser Foundation Health Plan warned that doctors make decisions based on how specific methods help specific patients - not how they compare to other preventive methods.

"We have a long way to go before we can establish airtight cases for one service over another across the spectrum of health care interventions," Dr. David M. Lawrence said.

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