Would you want to go through a screening test to find out if there is anything wrong with you, even when you are feeling fine?
Perhaps, that would depend on which of these stories about the benefits and pitfalls of screening you believe the most.
You might have read, in an article about cancer, the terrible, and even fatal consequences, a man or woman has to face because they went to their doctor's office a little too late.
Or, on a more positive note, you might have heard about someone who was saved from misery just because a random or routine screening test showed that they had early signs of a potentially dangerous condition like diabetes.
Then you hear extreme, but relatively rare stories, like this one in the latest issue of Newsweek, one which writer Sharon Begley had used to illustrate the potential hazards of over-investigation and searching for conditions that might not have created harm if left alone.
"In 2009, a 52-year-old woman with chest pain underwent a cardiac CT at a community hospital. Neither her LDL (bad) cholesterol nor her C-reactive protein (another risk factor for heart disease) was elevated.
"But since the CT showed several coronary plaques, her physicians performed coronary angiography (an X-ray of the heart arteries). Complications ensued, and the woman wound up undergoing more procedures, one of which tore an artery."
Dr Steven Nissen, a cardiologist at the Cleveland Clinic who related that story, commented, "She eventually went to the Cleveland Clinic for a heart transplant - not because she had heart disease when it all started, but because of the cascading interventions triggered by the CT."
All these stories may be true, but believing the success stories of screening tests without considering the risks or harm they can bring, or vice versa, is problematic. For starters, some may go for a wide array of tests and scans every year just to reassure themselves, and others avoid such tests as often as they can due to the fear of finding something sinister.
But how can you walk the middle path?
"To pick up common diseases like diabetes and hypercholesterolaemia, an annual checkup is a good idea, compared to no checkup at all," says Dr Ng Soo Chin, a consultant haematologist in private practice and the past president of the Asean Federation of Haematology.
The debate, however, is often on the extent and timing of screening, and the kinds of tests a person needs during those checkups.
"I think the public needs to be aware of how (medical testing) works and what is beneficial for them, instead of doing a blanket of tests," says Dr Alex Tang, a consultant vascular and interventional radiologist at the Sime Darby Medical Centre.
The medical sieve
The medical sieve
First of all, what are screening tests, and why do doctors order them?
Generally speaking, a screening test is a test that is designed to detect early signs of a disease or the risk of developing a disease in people who are well and do not show signs of the disease.
As consultant in public health to the UK National Health Screening Programmes, Angela Raffle described to a UK publication, Making Sense of Screening, that tests are medical sieves doctors and public health experts use to catch people who are at risk of a disease and allow those not at risk to pass through.
Sometimes, people who are not at risk will get "caught" by the sieve. These are called false alarms. There are also those who are at risk but "pass through". These are called false negatives.
However, all those who are picked up by the sieve will be advised to go for more testing to determine if they have the disease and need treatment.
Sometimes, a test used for screening can also be the same one that is used as a diagnostic test, which doctors order to find out if there is an underlying disease that is the cause of a patient's signs and symptoms.
When a test is ordered after a patient has symptoms, it can be used to help plan his treatment, evaluate the response to treatment or monitor the course of the disease over time.
With so many tests to choose from today, how do you know which are the ones you need?
A competent doctor can help you with that. "A person who is going to be screened or tested should have a proper medical history and physical examination done, because it is possible to do many tests and still miss out on the primary problem if you are not guided by the clinical findings," says Dr Ng.
As the tests we may need are dependant on factors such as age, sex, family history, past medical history, lifestyle, occupation, and current medical problems, it is important for our doctors to have this information before they can order any blood tests.
For example, if you are young and do not have symptoms of rheumatoid arthritis (pain or stiffness in the joints), you do not need a test for your rheumatoid factor (a test usually used to differentiate rheumatoid arthritis from other forms of arthritis).
This is because it would be highly unlikely that you would have the disease (a diagnosis has to be made in conjunction with the symptoms), and a positive result can also be seen in many other conditions and even healthy people.
These details are different for every test and scan that is available out there, so it is wise to seek professional help.
"Ideally, the person who ordered the test for you should be there to interpret the test results as well," says Dr Ng.
As your test results can be affected by many factors other than the diseases they are supposed to indicate, they have to be interpreted in the light of the correct setting.
Sometimes, blood test results are affected by specific foods, the drugs a patient is taking, and the patient's compliance to pre-test instructions. For example, says Dr Ng, a smoker tends to have a slightly raised white cell count, and hence, this should not raise any alarm.
However, when these factors are excluded, follow-up actions on abnormal results are critically important to ensure speedy diagnosis and treatment of the underlying disorders.
Balancing benefits, risks and harm
Experts who contributed to Making Sense of Screening agree that some screening tests that are offered to the public can be used to identify some of the people most at risk of a disease so that they can be offered early treatment.
However, they are also quick to mention that these benefits have to be weighed against the potential harm the tests can cause. They include direct harm like side effects from the tests, and indirect ones like false alarms, undue anxiety, and unnecessary treatments over an abnormal test result, or false reassurance over a positive result.
They were speaking about the considerations that should be included before the rollout of a national screening programme, but the principles apply to individual cases as well.
For radiological tests like X-rays and CT scans that expose those who undergo them to radiation, Dr Tang says that the test needs to be justified, optimised, and done with a radiation dose that is as low as is reasonably achievable.
That means, a radiological test that exposes a person to radiation must be done with a justifiable reason (whether to check out a symptom or monitor a disease), after considering other tests that can achieve the same goals with less radiation or cost.
While blood tests usually do not involve radiation, having too many unnecessary ones may cost you more and sometimes distract your doctor from what is really important.
A battery of tests, no matter how extensive, can never be exhaustive enough to capture all the things at once, says Dr Ng. That is why it needs to be personalised to each patient.
As Dr Ng observed in his practice, over-investigation (doing too many tests) and under-investigation (too little) both have their downsides.
"Those who really need the tests probably do not have them done as quickly, or as many as they should," he says. "So, if you are really sick, don't just go for a screening test. See a doctor so he or she can guide you along and advise you on the appropriate tests to take," he says.
But if you are feeling healthy, can afford a check-up, and would just like to have your health checked out, it is okay to have some tests done.
However, before you sign up for the whole list of tests, it would be wise to consult a doctor to find out whether you need them and make sure you understand the risks involved in these tests. And when you get your results, do get your doctor to review and explain them to you.
While every test strives for the highest achievable accuracy and specificity, there is no such thing as a perfect test or battery of tests.
Should you get tested?
Should you go for that test?
While your doctor may not be able to explain every detail about the tests they are about to order during your short consultation, here are a few questions the US National Institute of Health says you can ask to find out more the tests you are about to undergo.
- Why is the test being done?
- What steps does the test involve? How should I get ready?
- Are there any dangers or side effects?
- How will I find out the results? How long will it take to get the results?
- What will we know after the test?
Generally, a test should be able to aid your attending physician in either diagnosing a condition you have, monitoring the progress of your disease, or predicting the course of your disease.
However, if you are unsure about the dangers or the side effects of the test, you can also ask your doctor if there are alternative tests you can consider.
For those interested in reading more about screening tests, Making Sense of Screening and Making Sense of Testing are available for download at their publisher's website, www.senseaboutscience.org.