One-third of patients who visited 3 or more docs affected by medical error.

About 1/3 of patients who visited 3 or more physicians a year were affected by a medical error or prescription drug error, according to a Harvard University study.

The study of sick adults, which was conducted in the US, Canada, UK, Australia and New Zealand, found that 25% of patients with health problems have been affected by a medical mistake or prescription error in the past 2 years.

The study, which surveyed at least 750 people in each country, revealed the US had the highest portion of reporting errors-28%--and the UK the fewest, 18%. However, in all 5 countries, people who went to more than 2 physicians reported twice as many errors as those who went to 1 or 2 physicians.

"The biggest risk is when you're seeing multiple doctors who are doing lots of tests and prescribing a lot of drugs," said Robert Blendon, the Harvard professor who led the study. "It's lack of coordination. If you're taking Coumadin given by one doctor, then you maybe shouldn't be taking another drug given by another doctor."

More than 1 in 4 (28%) people of those who reported seeing more than 2 physicians in the US or Canada were given duplicate tests by different physicians, the survey found. In addition, about 25% in all 5 countries reported getting conflicting information from different physicians.

A 1999 study conducted by the US Institute of Medicine found that medical errors may be responsible for killing 44,000 to 98,000 Americans annually.