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The customary annual physical check-up at the doctor's office may not be worth the time or money, say researchers.

About 63 million United States adults visit a doctor annually for a routine medical or gynaecological check at a total cost of US$7.8 billion ($10.63 billion), according to a study intended to help answer questions about the value of this trip.

More than 80 per cent of preventive care provided by doctors does not happen during this check-up, the study showed. And more than US$350 million worth of potentially unnecessary medical tests are performed.

"We need to question encouraging everybody to come in for an annual physical," said Dr Ateev Mehrotra of the University of Pittsburgh School of Medicine and the Rand Corp, who led the study.

"There's a lot of money, a lot of visits, a lot of adults going to see their doctor for annual physical exams with a real unclear benefit. It's the No 1 reason adults see their doctor, and yet we don't know whether it's helpful."

The checks account for one in 12 adult outpatient visits to the doctor's office, the study found. On average, they lasted 23 minutes and cost US$116, including laboratory and radiology services.

The study also documented differences across the country in routine annual physicals. People in the northeast are far more likely to get them than those in the west. The kinds of care and testing provided by doctors also varies by locality.

Many patients were routinely given laboratory tests such as complete blood cell counts or urinalyses of uncertain medical value in the absence of a specific reason.

Dr Mehrotra said no major North American clinical organisation advised people to get an annual medical check, but most adults thought they should get one and most doctors recommended them.

"I'm not saying preventive care itself is not helpful. It is clearly helpful - mammograms, pap smears, cholesterol screening, colon cancer screening, prostate cancer screening. And patients should get those. But does it need to happen at this special visit? Or can we get it some other way?" he said.

The institution of the annual medical check-up, intended to detect or prevent unseen health problems, dated back about a century in the US, Dr Mehrotra said.

But large studies in 1960s and 1970s failed to show these checks provide a significant medical benefit to the patient and there has been a debate about their value ever since.

The researchers examined Government survey data from 2002 to 2004, and questioned doctors nationwide about what they did during the check-ups.

Only 20 per cent of eight preventive services tracked by the researchers were performed at these check-ups as opposed to during other types of visit to doctors, the study showed.

"Is a physical harmful at all? To the patient, there's likely little harm. The potential downsides of a physical are the money and people's time," Dr Mehrotra said.

The study appears in the Archives of Internal Medicine.

- Reuters