Using CT for screening unjustified

Date:05/01/2006 URL: http://www.thehindu.com/thehindu/seta/2006/01/05/stories/2006010500041600.htm Sci Tech

Using CT for screening unjustified

Virtually all the scientific and professional associations think risks are not overstated

# Cardiac CT cannot detect soft plaque, the earliest form of coronary artery disease
# Each examination dose is equal to that in several hundred chest X-ray tests
# There is no outcome data available that validates its use in asymptomatic individuals


RECENTLY, A Mumbai daily published a colourful advertisement. `Know in time,' the heading splurged in bold letters, `Heart study in 8 seconds.'

According to another advertisement in another daily `Now discovering the state of your heart vessels is as quick and easy as having a cup of tea.'

The advertisements persuade a potential patient to believe that a computed tomography (CT) procedure to evaluate the heart would be beneficial. Any CT procedure is unjustified if it is not medically necessary.

Universal risk factors

As CT procedure is `non-surgical,' regular check up of the heart is possible; the first advertisement assured the reader. The centre invited patients with some universal risk factors such as `stress' and `erratic life style (long working hours, pressure and the like)' for the test.

As any city dweller may suffer from any one or more of the listed risk factors, the advertisement aims at mass screening of asymptomatic persons.

The risk factors highlighted in these ads were not identical. The coronary arteries supply blood to heart.

They may develop blockages due to formation of plaques, which consist of fat and other substances including calcium. CT can help the physician to get information on the location and extent of calcified plaque.

Specialists use CT for angiography or calcium scoring for evaluating coronary heart disease. Modern CT angiography helps to get clear images of the arteries non-invasively.

According to RadiologyInfo, a publication of the Radiological Society of North America, not all calcium deposits in the coronary arteries mean that there is a blockage, and not all blocked arteries contain calcium. Cardiac CT cannot detect soft plaque, the earliest form of coronary artery disease.

The relationship of calcium score to the likelihood of experiencing angina, myocardial infraction and sudden death remains uncertain.

"A screening application is currently not supported by the study data published. ... .I cannot recommend screening application... "

"Therefore, aggressive marketing strategies using the method in the context you described will face troublesome litigation in most countries," Professor Martin H. K. Hoffmann, Department of Diagnostic Radiology, University Hospital, Ulm, Germany, responded to an e-mail query.

In the May 25, 2005 issue of the Journal of the American Medical Association (JAMA), he described the potential of Multi Slice Computed Tomography (MSCT) to complement invasive coronary angiography.

Balancing benefit ,harm

Each CT examination exposes the patient to a dose equal to that in several hundred chest X-ray tests... "A screening application needs to balance benefit and harm"..."We therefore deem scanning only appropriate in patients with symptoms of unclear origin and high risk profile patients with positive stress test results", Dr Hoffmann cautioned.

Dr Mario J. Garcia, Department of Cardiology and Radiology, Cleveland Clinic Foundation, U.S., concurred.

Specific guidelines

"There is no outcome data available yet that validates the use of this test in asymptomatic individuals...right now we don't have specific guidelines to what should be done with a positive or negative result.

"I share the reservations of the American Heart Association, American College of Cardiology, American College of Radiology and Food and Drug Administration, we use this test primarily in symptomatic individuals with very few and justifiable exceptions." He listed the limitations of MSCT in an accompanying editorial in JAMA.

"There is, of course, much interest in cardiac screening, but I do not think the evidence yet supports widespread screening", Dr. Thomas B. Shope, Center for Devices and Radiological Health, US FDA, replied to my query.

"We continue to see similar advertisements here in the U.S., but I do not think we have as many such facilities as we did a few years ago", Dr Shope reacted to the advertisement on CT screening in the Mumbai daily.

Responding to an e-mail query, Dr Bhavin Jankharia, a Mumbai radiologist, claimed that cardiac CTs, especially in high risk patients, even if asymptomatic, can help in deciding further life style changes especially in the presence of an increased plaque burden.

Considerable controversy

"I agree that not everyone should undergo cardiac CTs, but often the choice is made by the patient," he clarified. He conceded that there is considerable controversy about self-referral and the use of screening.

"We don't encourage self referrals for many parts of the body, including chest, brain and the like. But a good number of our cardiac CT patients are self referred." He believes that the risks of radiation are over-stated.

But virtually all the scientific and professional associations think otherwise.

The professional associations dealt a body blow to commercialised CT screening in the U.S. Will it happen in India? The advertisements with unsubstantiated claims, condition the patient to go for the test.

The day is not far off when we will see a tennis/cricket player or a film star in India endorsing CT scans!

K.S. PARTHASARATHY

ksparth@yahoo.co.uk
(The author is former Secretary, Atomic Energy Regulatory Board)

© Copyright 2000 - 2006 The Hindu