mm Hg in systolic blood pressure between the two arms of nearly a quarter of his patients. In one case, the difference was 20 mm Hg.17
Things are just as confusing for pregnant women and children. Doctors and health-care workers can’t even agree over how to record the second beat of blood pressure (called the diastole), which measures when blood fills up the heart,18 or whether certain sounds accurately reflect diastolic pressure. This was even the subject of a heated debate at a world congress of hypertension in pregnancy in Italy, calling for an ‘international consensus’ on how to record blood pressure in pregnant women. In fact, some researchers have claimed that doctors have been using the wrong type of blood-pressure test on pregnant women: obstetricians and midwives prefer the blood-pressure gauge called Korotkoff phase 4, but research shows that phase 5 testing is far more reliable – the reverse of the prevailing view. In one test, virtually nobody agreed on the reading from a K4 test, while everyone was in agreement on the K5 test.19 As for children, the latest recommendations are that they, too, have ambulatory monitoring.20
This potential for different interpretations in readings can cause problems for you if your blood pressure is being monitored by several people who may have had different training in how to read the cuffs.
CHOLESTEROL TESTS
Today, a cholesterol test is the most-often sought diagnostic test of all. In a general check-up a doctor will routinely offer you one to determine whether if you are at risk of heart disease. The test measures the amount of cholesterol and triglycerides in the serum (the non-cellular part) of your blood.
A total cholesterol test, which is rarely used these days, will examine all the blood fats, including the overall cholesterol level, the LDL (low-density lipoproteins, or ‘bad’ cholesterol), HDL (high-density lipoproteins, or ‘good’ cholesterol), VLDL (very low-density lipoproteins), chylomicrons (fats that are present right after a meal but ordinarily disappear within two hours) and triglycerides (compounds in the body that shift fatty acids through your blood). However, the typical cholesterol test only examines the LDL cholesterol.
The test requires a relatively straightforward blood test. You are asked to fast for 9–12 hours before the test is taken. A tourniquet is applied to your arm, so that the lower veins will pool with blood, and the blood is drawn from a vein either on the inside of the elbow or the back of the hand.
All fat tests (lipids, as they are known in medicalspeak) are measured in terms of milligrams per deciliter of blood (mg/dL). Medicine rates as acceptable a total cholesterol count of less than 200 mg/dL. The current medical wisdom is that the higher the cholesterol count, the greater the risk of heart disease or atherosclerosis (clogged arteries), and that if your levels are over 240 mg/dL you nearly double your risk of heart disease, compared with someone in the normal range.
The (largely unsubstantiated view) is that high LDL cholesterol levels may be the best predictor of risk of heart disease; if you have no other risk factors, your LDL count should come in at below 160 mg/dL. People with diabetes, heart or vascular disease, other risk factors or a family history of heart disease should try to keep their cholesterol levels even lower, say doctors.
Medicine loves statistics, and nowhere is this more evident than with this test, where a high LDL is thought to be countered by a high HDL, and vice versa. HDL cholesterol levels of 60 mg/dL are thought to counteract other risk factors; HDL levels below 40 mg/dL themselves become a risk factor.
Even if you have low LDL and high HDL cholesterol, high triglyceride levels may put you at risk. For instance, a normal triglyceride level should be less than 150 mg/dL. A vast array of conditions can result in an inaccurate test – liver disease, an underactive or overactive thyroid, kidney problems, liver disease, malabsorption of your food (say from a leaky intestinal tract), pernicious anaemia, infection and diabetes that isn’t under control. Pregnant women and those who have had their ovaries removed also will register high on the test. An array of prescription drugs – beta-blockers, thiazide diuretics, steroids, phenytoin, sulphonamides, the Pill, even vitamin D – can also throw off your test.
The other problem is the inherent inaccuracy of the lab test itself. According to one study, some 70 per cent of samples analysed have evidence of bias in the computation of results21; other research shows the products themselves used to measure blood cholesterol have major drawbacks.22 In one Canadian study of total cholesterol tests, nearly one-quarter were misclassified (as, say high risk), nearly a fifth registered a false-positive (a high cholesterol level when it wasn’t) and among those in the ‘high risk’ category, half had a false-positive reading.23
A few people in medicine are waking up to the fact that LDL levels alone are not an accurate predictor of heart disease. A large British Health Survey for England found that forecasting heart disease was far more accurate when factoring in the HDL levels, too.24
ECG Readings
Besides blood-pressure and cholesterol measurements, your doctor’s next favourite activity is listening to the state of your heartbeat. However, these days, the all-purpose stethoscope (never proved to have any advantages over the naked ear) has been replaced by a number of space-age gadgets, all designed to record the most minute changes in your heart’s ability to do its job.25 The stalwart of any cardiac specialist is the electrocardiogram (ECG), even though studies demonstrate enormous potential for error in recording or interpreting correct results. One study showed that computers, often used to interpret ECG readings, were only right two-thirds of the time, and missed 15 per cent of cases of enlargement of the right ventricle. Nevertheless, human beings didn’t fare much better; even trained heart specialists misinterpreted one out of every four readings.26 This is largely because, as with blood-pressure, readings can be affected as much as 20 per cent by recent activity, time of day, and even factors such as fear of the cardiologist’s findings! The late Dr Robert Mendelsohn wrote of a study in which electrocardiography detected only a quarter of proven cases of heart attack, and another study in which the tests found gross abnormalities in more than half of perfectly healthy people.27 As Stephen Fulder, author of How to Be a Healthy Patient (Hodder & Stoughton), notes, an incorrect ECG has led to ‘vague diagnoses of organic brain disease in healthy but unruly children, turning them into medical cases’.28
More state-of-the-art these days than the ECG is echo-cardiography – a diagnostic test on the heart, often using a mixture of contrast agents and soundwaves. The procedure had been gaining acceptance for its safety and accuracy. However, as with much ‘perfectly safe’ new technology, doctors have only recently realized that it is more dangerous than had been thought, possibly leading to life-and-death complications.
The first major study into the procedure discovered that it can be life-threatening in one in 210 cases, requiring special treatment or a stay in hospital; two people of the 3,000 studied suffered a heart attack after the procedure had been completed.29
The procedure often employs the use of microbubbles of a contrast agent like octafluoropropane, which are useful in visualizing the tiniest blood vessels of the heart. In laboratory research, rats have developed cardiac arrhythmias after being exposed to echocardiography because the contrast agent interacted with ultrasound, causing the alterations in heart rhythms. Although animal models often don’t apply to humans, this effect on a living being demonstrates that pulsed ultrasound can interact with bubbling contrast