Wednesday, November 08, 2006

The right use of 64 slice MSCT

There has been much controversy over the usage of the 64 slice-MSCT. In the USA we are seeing issues over how good 64-MSCT is in general and, by extension, its accuracy, especially compared to conventional coronary angiogram. There are also concerns about the hazards of 64 MSCT, including radiation exposure risk. For these reasons, third party payers were wisely not paying for their use, except in some states.

In our country a new toilet can attract a good sized crowd to form a line. We assume that whatever technology, as long as it is sufficiently new and comes in a shiny enough box, is good technology. Lacking any governing body or legislation, without any meaningful control or sense of scientific scepticism, almost everyone who calls himself a medical centre and has enough money in his piggy bank has rushed out to acquire their own shiny machine. For those keeping score at home, the count is at least 7 64-slice MSCT machines in the Klang valley (6 million people) and at least 15 in the country (26 million souls). These are only the ones we know about.

A natural result is severe blatant abuse of the worst kind involving the machine and the technology it represents. In order to pay for their shiny new, and may we suggest expensive, toys, marketing departments are clocking up large amounts of overtime. After all, it's crucial that the 64 slicer be paid up by the time the 1024 slice multi gizmo doodad comes out to wow the gullible consumer. In this environment, can it be any surprise that we see business practices such as deceptive packaging and price undercutting start to take the wheels while medical interest is stuffed into the trunk with a hefty cement block tied around its legs. After all Return on Investment is king and the patient is just another customer relationship to be sucessfuly leveraged in the ihe interest of the all-important bottom line. regrettably enough, some medical professionals have been dragged into this "business".

It is very gratifying that Circulation on-line published a study by Dr Hoffman and colleagues, on the use of the 64slice-MSCT in the emergency department of their hospital. This paper is a good example of the basis on which this machine should be used, properly that is.

In the USA, hospitalisation and admission to hospital is a very expensive affair. Patients presenting to ER have to be properly screened so that the right ones are admitted and the right ones are sent home. The sight of a patient stumbling into the emergency room is not a sign to hoist the jolly roger on a broomstick.

Clinical approaches with the use of clinical signs and symptoms, with ECG and biochemical markers, have proven to be less then satisfactory. Using the clinical approach, 60% of admissions for ACS have proven unnecessary, and 2-8% of patients with chest pains, who were send home, had ACS. Can you imagine the medico-legal implications?

Dr Hoffman and colleagues used the 64-MSCT to accurately predict those who were presenting as ACS, but who actually did not have CAD and who could safely be send home They scored a negative predictive value (NPV) of 100%. Therefore many with non-cardiac chest pains (almost 60%) can safely be sent home without any medico-legal problems.

Locally, we have Dr Sim's work in the Sarawak GH producing valuable data on 64 slice usage. The GH there has a 64-MSCT. They are tracking their patients and doing correlations with conventional angiograms. They scored a NPV of about 97%. However, the positive predictive value (PPV) is only about 92-93%, and this value varies from vessel to vessel and portion to portion.

My opinion is that the 64-MSCT should (for the moment) be use in the ER to exclude the presence of CAD in those presenting with chest pains. There is at present inadequate data to support it's routine use in the diagnosis of CAD and it's use as a replacement for conventional coronary angiogram.

There is a study underway, called the PIOCAD (Prospective investigation of CAD), which will study the accuracy of 64MSCT in the diagnosis of CAD in those with stable angina. This study will include 1000 patients.

The sad truth is that, it may again be a case of too little, too late. The arms merchants are tooling up to supply all parties with even shinier toys. A 256 slice-MSCT is on the way, it claims with lower radiation hazards. For those thinking of buying one, it may be wise to wait a little. Those who already have one, you may have to try and recoup your capital costs, even at the cost of practicing medicine with one eye patch on.

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