NHS screenings may only lead to anxiety, warn experts Not all NHS tests have been validated by the UK Nat'l Screening Committee Routine exams for dementia shouldn't be offered - they aren't good enough Screenings for cervical cancer of women aged 20-25 create false positives Heart disease checks often result in patients taking drugs they don't need By Dr Margaret Mccartney So you've received a letter inviting you for screening - for bowel cancer, perhaps, or breast cancer - or your doctor says he needs to check you for the early signs of dementia. But will these actually help you, or could they end up doing more harm than good? For while screening can be life-saving, it can also cause anxiety, false positives and lead to tests and treatments - with side-effects - you might never have needed. All screening programmes - even those approved by the UK National Screening Committee (the official body that assesses which screening is worth offering) - are a mixture of pros and cons. Checklist: All screening programmes are a mixture of pros and cons The problem I find, as a GP, is that the official literature about these programmes highlights potential gains far more than possible downsides. This is a highly contentious subject. Certain screening programmes, such as breast screening, cause enormous rifts in the medical community, with some doctors saying that it doesn't work and proponents vehemently disagreeing. So where does that leave you, the patient? First, you need to be clear what screening is. Screening tests are done only where there are no symptoms of disease. So if you have a worrying lump or abnormal bleeding, you need to go to your GP for appropriate diagnostic tests. Unfortunately, every so often I hear about someone who knows she has a lump, for instance, but has waited patiently for a breast screening appointment (all women aged between 50 and 73 are invited for a routine three-yearly mammogram). This isn't the right kind of appointment. What these women need is not just the mammogram they will get with the screening, but usually an ultrasound and biopsy. It's also important to understand that not all the tests the NHS is offering have been validated by the UK National Screening Committee. These experts look at the evidence for screening - just because it sounds sensible to test for diseases before you know you have them, often, when the research is done, the screening just doesn't work. One example is ovarian cancer screening. This often isn't diagnosed until it is at a late stage, so screening sounded a good idea - unfortunately, large trials where women at high risk (because of their family history) were given blood tests and ultrasound scans found that screening this way didn't save lives. Furthermore, it created a lot of false positives. The hunt is on for a better test. Here we look at screening tests offered by the NHS - and what you need to know before you decide to have one. Until now, diagnosing dementia has been a matter of the patient, or their relatives or friends, going to see their doctor about their symptoms. But the Government has recently told GPs that they must call in people over the age of 60 with any risk factor for dementia - such as a history of stroke or heart attacks, or diabetes, or vascular disease - for dementia screening. This means people who have not noticed any memory problems will be asked to make an appointment for screening. Not up to snuff: The UK National Screening Committee thinks that routine screenings for dementia shouldn't be offered because there isn't a good enough test - or enough advantages for patients However, in 2010, the UK National Screening Committee reviewed all the research and decided that routine screening shouldn't be offered because there wasn't a good enough test - or enough advantages for patients. It will certainly lead to many people being told they might have a problem when, in reality, they don't. Other people will be diagnosed with 'mild cognitive impairment', which only leads to dementia in a minority of cases. This will cause a great deal of concern and anxiety and many GPs (including me) have objected to this new screening programme because there is no evidence showing it will be useful. The £21 million being spent on screening invitations might be better spent on people who actually have dementia. Women between the ages of 25 and 64 are offered a three-yearly cervical screening - a smear test - to check for cervical cancer. If this shows minor changes in the cells, the cells are then tested for human papilloma virus (HPV), the major cause of cervical cancer. If positive, the woman will be given a colposcopy, where the cervix is examined using a type of microscope. The NHS says cervical screening can prevent three in four cervical cancers. Some women find testing unpleasant, and there is a risk of a false positive, where cell changes are found on the smear but would have got better by themselves. This can lead not just to anxiety but to treatment (removing the cells, usually using heat) that wasn't necessary. The biggest recent controversy has been the change in age of screening from 20 to 25. The evidence is undeniable: large studies found that screening under-25s creates many false positives - cell changes in this age group that clear without treatment. These common changes led to unnecessary tests and treatment - and didn't reduce cervical cancer death rates. Many young women who have had cervical cancer say that screening under the age of 25 would have helped them. Crucially, though, most of these women had symptoms - such as bleeding after sex - which meant that screening wouldn't have been the right test for them; they needed diagnostic tests, which are available at any age. Unnecessary risk: Most aneurysms don't burst - so some will have an operation they don't need but will still suffer the side-effects of surgery An aneurysm is a weakening in a blood vessel, in this case causing a bulging of the aorta, the main blood vessel from the heart. Screening is offered to men aged 65 - they are at higher risk than women - in the form of an ultrasound of the aorta. The problem is not the aneurysm itself, it's what happens if it bursts, when it is often fatal. In general, it's better for patients to have the aneurysm repaired in a planned way rather than as an emergency when it has burst. The NHS says the screening programme aims to reduce the death rate from burst aneurysms by up to 50 per cent, and the UK National Screening Programme has approved the scheme. But you also need to know the risks. A large study published in the British Medical Journal has reported that screening could almost halve the death rate from aortic aneurysm in men over 65 (the risk went from just under 1 per cent to just below 0.5 per cent). Aneurysms are relatively common - one man in 25 has one - but most don't burst. And surgery (offered to men with large aneurysms) has risks, including bleeding. The death rate for this major surgery is between 1 and 6 per cent. Because we can't be sure which aneurysms will rupture, this means some men will have an operation they don't need but can still suffer the side-effects of surgery. Every person in England between 40 and 75 is going to be offered an NHS Health Check, 'helping you prevent heart disease, stroke, diabetes and kidney disease'. Essentially it involves checking your weight, height, blood pressure and cholesterol -with a diabetes and kidney blood test for people with high blood pressure. The idea is to catch high-risk people early and get them to make changes to their lifestyle which can reduce the risk of future disease. However, screening everyone in this way, no matter how low their risk, hasn't been shown to save lives or reduce disease. A large trial of screening for diabetes on UK patients published last year in The Lancet showed that it didn't save lives. Then last month an authoritative Cochrane review assessed the evidence, the authors saying that the Health Check Programme works 'in direct conflict with the best available evidence' and is likely to lead to patients taking drugs they don't need. The Health Checks programme doesn't have the approval of the UK National Screening Committee - or of many GPs. 'Screening everyone in this way, no matter how low their risk, hasn't been shown to save lives or reduce disease.' One major concern is about overtreatment, ie, giving people pills from which they will never benefit. Treating people who have had a heart attack or stroke with statins has been shown to reduce their future risk of another. But it's different for people who have no cardiovascular disease. It's estimated that 100 people without known cardiovascular problems have to be treated with a statin for five years to stop two heart attacks or strokes. Many people on statins complain of side-effects such as muscle aches or tiredness, and statins also slightly increase the risk of diabetes. Men and women aged between 60 and 69 are sent a screening kit every two years. By 2014 this will be extended to age 74. A sample of stool is sent to the lab and tested for traces of blood. Most people will test negative, but two in 100 will have a positive result and be offered a colonoscopy, a telescope examination of the bowel. In 10 per cent of these cases, the colonoscopy will find bowel cancer and another 40 per cent will have a polyp (growth) removed, as some can become cancerous. The main problems are the risk of a false positive - half of the people given a colonoscopy because of a positive screening test turn out to have a normal bowel, so they had a colonoscopy they didn't need. Colonoscopy comes with a risk of its own - for example, bleeding, or perforation of the bowel, which the NHS says happens once in every 1,000 times. It's important to keep the risks and benefits in proportion. The NHS is technically correct in saying that the screening programme can cut the risk of death from bowel cancer overall by 16 per cent. However, to make sense of this you have to know what your risk is to start with. This varies by age and sex. As an example, without screening, 70 in a group of 10,000 men aged 60 will die from bowel cancer in the next ten years. If the same group is screened, the death rate can be cut to 52 out of 10,000 - a small overall difference. Caution: Because the treatment for breast cancer can be harmful, the pros and cons have to be carefully weighed up All women aged 50 to 73 are invited for a routine three-yearly mammogram. The UK National Screening Committee has approved this scheme, which has been running for 25 years. However, in recent years there has been controversy about how effective it is, with several key studies showing that more women than previously reported ended up having unnecessary treatment, including mastectomy. An official review was set up to report on the evidence and last year concluded that breast screening did save lives, but at a cost. It estimated that out of 10,000 women screened, 43 would not die from breast cancer as a result of screening. However, 129 would be diagnosed and treated for cancer they would never have known about otherwise and which, crucially, would not have harmed them. Because the treatment for cancer can be harmful, the pros and cons have to be carefully weighed up. From this month, the leaflet that accompanies the invitation for screening will explain the drawbacks for the first time. Dr Margaret McCartney is a GP in Glasgow and author of The Patient Paradox - Why Sexed Up Medicine Is Bad For Your Health (Pinter and Martin, £9.99).