Health screening: are they needed?

SINGAPORE - I often see patients for health screening and they often ask me what is the health benefit of such screening.

The truth is that health screening is useful for detecting chronic diseases, such as diabetes, hypertension and hypercholesterolemia; and certain cancers such as cervical cancer, breast and colorectal cancer.

In Singapore, the Health Promotion Board subsidises health screening for Singaporeans who are 40 years old and above. The aim is to detect those who are asymptomatic but may well have chronic diseases, such as diabetes and hypertension.

The burden of chronic disease is growing rapidly in urban societies. In Singapore, we are looking at a diabetic rate of about 10 per cent of the population. If you take away children of school-going age, you are left with a statistic of one in five adults above the age of 30 who are diabetic. In those who are above 60 years of age, one in three are diabetic.

For hypertension, we are looking at one in five adults who have the disease and in those above 60, it is one in two.

In the case of raised cholesterol, we are looking at a frequency of one in six adults.

Obesity has a rate of about one in 10 adults.

For breast cancer, we had 8,000 new cases over a five-year period from 2007 to 2011.

For colon cancer we had 8,400 new cases over the same period.

From a statistical point of view, it certainly makes sense to screen for chronic diseases, obesity and certain cancers. On a more practical note, seeing your family doctor for a health screening is important. Your doctor will take your blood pressure to see if it is normal. We are essentially looking at a reading of 130/80 mmHg and below.

Sometimes, if it is raised due to anxiety or "white coat" hypertension, your doctor will repeat the reading after you have calmed down. If the reading is persistently raised, your doctor will not diagnose hypertension in one visit. Usually, we will look at the blood pressure over at least three separate occasions before a diagnosis of hypertension is made.

There is technology where we can strap a blood pressure monitor on you to wear for 24 hours and about a hundred readings are taken. We will diagnose "true hypertension" if half or more of the readings are above 135/85 mmHg. Diagnosis of hypertension is important because if left untreated, we are looking at a stroke rate of about 40 per cent more than those hypertensive patients that are well controlled on medication.

At your family doctor, most certainly blood tests will be ordered and for diabetes, a fasting blood sugar is important. If raised at 8 mmol/L or above 108 mg per cent, the result will trigger further evaluation. Sometimes a test called haemoglobin Aic is also done and this test measures your average blood sugar levels in the last three months.

A level of 6.5 per cent or more will certainly indicate that the patient is diabetic.

Finally, the gold standard test to diagnose diabetes is still a challenge test called the glucose tolerance test. This involves drinking a glass of glucose and measuring your blood sugar levels three times to see if you body can handle a load of sugar. In short, I will call it a sort of stress-testing of your body's ability to handle a sugar load.

The blood test will also measure your cholesterols profile. The important test would be your level of LDL or "bad" cholesterol. Most of the data we have from clinical trials involves the LDL levels and therefore your total cholesterol levels are not that helpful without a breakdown into your bad/LDL and good/HDL cholesterols.

We prefer to have LDL cholesterol of 130 mg per cent and below, though an ideal level would be 100 mg per cent and below. For the HDL cholesterol, we would like your level to be at least a quarter of your total cholesterol readings. In the case of HDL cholesterol, the higher the better. These desirable readings are also termed as "target" cholesterol levels to aim for.

These readings, along with your age, blood pressure readings, gender and whether you smoke or have diabetes would influence a risk score also known as the Framingham score. This is named after a famous town in Massachusetts where the study began in 1948 and is now still going on in the third generation of patients. A score of 10 per cent and above is considered high and means that the chance of having a heart attack is 10 per cent in the next decade of your life. The Framingham risk calculator is available online and easily accessible.

On the matter of health screening for cancers, the No 1 cancer for women is breast cancer.

In the US, one in eight women in their lifetimes will have breast cancer. In Singapore, it is one in 20 women in their lifetimes and rising.

In Singapore we are advocating annual mammograms for women aged 40 to 49; biannual mammograms for women aged 50 and above.

There are theories that point to obesity and higher intake of saturated fat in our diets. We have also noticed that girls are experiencing menarche or first age of menses at a younger age. This is also coupled with later ages of first childbirth as women delayed starting their families for various reasons. We think that breast changes during pregnancy and breast feeding do confer some protection against breast cancer.

Hence, the period where the "virgin breast" is exposed to estrogens in the body is lengthened between early menarche and late onset of first childbirth. This could possibly explain rising rates of breast cancer in urban societies.

Many options

At times, my patients ask me why they need to do an ultrasound of the breast with their mammograms. This is because there are two types of tissue in the breast comprising fat and connective tissue such as collagen. Asian women tend to have more connective tissue than fat and hence their breasts are denser. The density is better appreciated with ultrasound.

The other cancer for which we advocate screening is colorectal cancer. This can be screened for with a fecal occult blood test. The intestine will digest blood the same way it digests other proteins. Hence the blood that comes out in the stool is not fresh blood but "digested" blood.

The new generation of such tests now detect for components of the haemoglobin molecule with antibodies or even looks for human DNA and test for alterations associated with cancer. Hence, the accuracy and detection rates for such tests have increased over previous generations of fecal occult blood testing.

All said, the gold standard is still the colonoscopy. The procedure is very well tolerated today because of advances in sedation so much so that the main complaint is the drinking of the liquid laxatives the night before!

Colonoscopy offers the option of removing pre-cancerous polyps at the same sitting. With polyps, size matters, and when the polyp reaches a diameter of one centimetre the chances of finding cancer cells will be exponential.

With removal of the polyps, the problem is nipped in the bud. It is worth mentioning that colonoscopy is encouraged by generous Medisave withdrawal limits with minimal out-of-pocket expenses.

And if you are 50 and above, do consider doing a colonoscopy regardless of how well you feel. I also encourage my patients to have a gastroscopy at the same sitting.

There are many options in the realm of health screening. It's like an extensive menu in a restaurant. You have tumour markers for prostate, liver, pancreas, nose, ovary and breast.

There are magnetic resonance scans for stroke screening, brain aneurysms and breast imaging for those who carry breast cancer genes.

There are treadmill stress tests, CT and MRI scans for coronary arteries and ultrasound for abdominal aneurysms.

You have audiograms for hearing loss, retinal photographs for diabetics and bone density to detect osteoporosis.

It is important to have a discussion with your family doctor to decide which test is necessary and useful especially for those who have risk factors or predispositions.

In recent years, the US Preventive Services Task Force, the eminent authority on screening in the US, has advocated that the prostate cancer marker not be used for screening and that mammograms be only recommended after the age of 50.

The thinking behind these guidelines is that prostate testing in men and mammograms in younger women often result in psychological harm from false positive results, unnecessary biopsies, complications arising from these procedures and overtreatment of cancers that may not shorten a patient's life.

These guidelines about prostate and breast screening seemed to be at odds with how most of our local doctors think. Perhaps that's because the medical-legal environment is very different in the US and that leads to defensive medicine and therefore more biopsies to negate the legal risks.

Finally, as in all choices, one must make them in the light of favourable benefit and risk analysis with reasonable yield from the testing and all this should be guided with good advice from your family doctor.

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