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Planning Retirement Online

Health Screening
                                 August 2006





Screening in Disease Prevention: What Works?

Health screening is a controversial subject. Those in favour say that it helps to detect disease before symptoms appear, leading to improved prognosis, while opponents argue that screening may lead to unnecessary and costly follow-up and that early detection has not been proven to improve outcome. Private health screening can offer some tests that are not available on the NHS. Should patients be encouraged to have these tests?

A conference organised by the European Scanning Centre was held at the Royal Society of Medicine earlier this year. The conference heard from specialists on the current evidence for screening and also debated whether private health screening is of benefit or just “panders to the worried well”


What is the evidence for screening?

Coronary heart disease

Dr Duncan Dymond (St Bartholomew’s Hospital, London) discussed screening for coronary heart disease with electron beam computed tomography (EBCT). This was, he said, a subject that caused fierce debate among cardiologists.

His view was that it was a useful screening test and could potentially lead to more appropriate use of statins.

“EBCT detects coronary artery calcium and may help us to institute prevention at an early stage,” he said. Calcium is collected at sites of inflammation and there was a good correlation between coronary calcium and plaque volume. Measuring coronary calcium could predict coronary events. Studies showed that risk of events, such as myocardial infarction (heart attack), was highest in patients with the highest calcium score.

A major criticism of EBCT was that it could not detect soft, non-calcified plaque, which was the type most likely to rupture and cause myocardial infarction. However, soft plaque probably always co-existed with calcified plaque. “What a high score identifies is the vulnerable patient, not the vulnerable plaque,” Dr Dymond said.

Cardiac artery calcium screening is currently only available in private centres. “We should be able to do EBCT in the NHS to look for evidence of coronary inflammation and not just put patients on a statins on the basis of a cholesterol level,” Dr Dymond said. There were many people on statins who did not need to be. For a relatively small investment, it would be possible to cut the statin budget, or at least redirect the drugs to people who most needed them.

Aortic aneurysm

There is clear evidence of the efficacy of ultrasound screening for abdominal aortic aneurysm (AAA) said Mr Mohan Adiseshiah (University College Hospital, London). Clinical trials showed reduction in rupture rate and in mortality in screened patients. Screening was also cost effective: possibly at 4 years and definitely at 10 years.

The case for screening is proven and a national NHS screening programme is expected to happen, Mr Adiseshiah said.

“Ultrasound screening is well-validated, simple, quick, and completely non-invasive,” he said. Testing could be carried out by trained ultrasonographists. “There’s no reason why it couldn’t be done in a side room of a supermarket.”

AAA was more common in men than women, with an incidence of 5% in men aged 65 and over. Rupture occurred when the aneurysm reached a critical diameter, but the aneurysm growth rate was irregular and unpredictable.

Prostate cancer

Screening for prostate cancer by measuring PSA is one of the more controversial of the screening tests. Professor Roger Kirby (St George’s Hospital, London) said that the test’s value remained to be determined.

There was no question that earlier diagnosis of prostate cancer improved outcome, but PSA lacked sensitivity and specificity as a screening test. Around 20% of patients with prostate cancer in one study did not have raised PSA. “We need to wait for the results of the randomised studies currently underway to know whether PSA screening reduces morbidity and mortality”, said Professor Kirby.

A promising new test was the PCA3 (or uPM3) test, using a urine sample collected after prostate massage. Early data suggested this could have better sensitivity and specificity than PSA.

Professor Kirby said that for men with a family history of prostate cancer
he would advise PSA screening from age 40, and for others from age 50. He would probably recommend annual screening.

Colon cancer

One in 20 people will get colon cancer and half of them will die from it. The cancer arises from adenomatous polyps. Screening can therefore look either for polyps (which can be removed before they turn into cancer) or for early stage (curable) cancer.

The question with colon cancer is not whether to screen but which of the many tests to use, said Professor Steve Halligan (University College Hospital, London).

A colon cancer NHS screening programme is currently being introduced. This is based on measuring faecal occult blood. It detects cancer but not polyps, so is no good for cancer prevention.

The newest test is CT colonography (CTC, or “virtual colonoscopy”).

Professor Halligan said that CTC had great potential for screening as, like colonoscopy, it seemed accurate for both cancer and polyp detection. “The CTC test characteristics are good, it is acceptable to patients, and far safer than colonoscopy, but we need more data.”

Professor Halligan suggested that CTC might be particularly useful for older patients who were more likely to have problems with the more invasive endoscopic tests.

Lung cancer

Professor Peter Armstrong (St Bartholomew’s hospital, London) discussed use of low-dose chest CT to screen for signs of lung cancer.

The aim was to detect disease at an early stage when it was curable with surgery. Screening had been shown to be effective in diagnosing asymptomatic early stage lung cancer. But it was not yet known whether this had any effect on mortality.

“I am still sitting on the fence on this,” he said.

Earlier diagnosis could not be assumed to equate to reduced mortality. For example, screening tended to detect slower growing tumours (from which the patient might not die) and miss fast growing tumours. Randomised controlled trials were needed to assess cost and effectiveness. Results from such trials would not be available for several years.

Also, 90% of nodules identified at initial CT screening were benign. Patients needed to know that false-positive results were common and that further tests might be needed.

Professor Armstrong said that CT was certainly more effective than chest x ray for lung cancer screening.


“Private health screening panders to the worried well and is of little benefit.” True or false?

Private centres offer some screening tests that are not routinely available on the NHS. The pros and cons of private screening were debated. Professor Peter Dawson (University College Hospital, London) argued that CT screening was a “dubious exercise” for which virtually none of the criteria for a screening programme were met. There was often no sound trial evidence of effectiveness in reducing morbidity and mortality. It was hard to argue against individuals opting for private screening, but there could be large follow-on costs elsewhere in the health care system.

There were four possible outcomes from a screening test.


  • With a true-negative outcome, patients would be reassured but this may encourage continuation of unhealthy lifestyle.

  • A false-negative result would give false reassurance and the patient may ignore later signs and symptoms so the actual diagnosis was delayed.

  • False-positive results were common with CT and “turn healthy people into patients, at considerable expense.”

  • Finally, a true-positive result meant that disease was found earlier, but that did not necessarily mean that the patient would live longer.

Professor Dawson said: “The worried well are frequently falsely reassured, reinforced in their unhealthy lifestyles or, worst of all, made more worried.”

Private screening was the individual’s choice. The public was better informed these days and people knew that tests were available that were not offered by the NHS.

“Private health screening can fulfil all screening criteria in the right hands,” said Dr Paul Jenkins (European Scanning Centre). The advantages included early detection of sub-clinical disease, potentially leading to improved prognosis and less radical treatment, the ‘worried well’ become the ‘reassured well’, ie, it gave peace of mind, and it led to greater health awareness.

Private health screening could also be effective for carotid stenosis, testicular, ovarian cancer and of course breast and cervical cancer (both the latter available on the NHS), and osteoporosis.

Potential hazards of screening could be reduced by experienced radiographers and optimised equipment. CT involved a considerable radiation dose though no-one yet knew the risk to patients of the doses used in screening programmes.


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