THE internet has been a mixed blessing when it comes to healthrelated matters.

At one level, it's given people access to vast amount of medical information. Then on the other hand, how much of it can we trust? The area of self-test kits is a particular cause for concern. Diagnoses from menopause, to flu, fertility, HIV, asthma, diabetes and cancer are promised for as little as 5. This can be very tempting considering that the average visit to a GP costs 50, and more if blood tests or scans are required.

But the validity of these self-tests is questionable. A recent study by the University of Birmingham concluded that while these tests have potential benefits such as privacy, convenience and speed, they can also cause stress, due to erroneous results and carry risks if they provide false-negative results.

The researchers collected data on 167 tests advertised by 19 retailers, which required samples of blood, stool, saliva, semen, urine or vaginal discharges. These samples were processed at homes with results either available in minutes or sent to a laboratory, whereupon the results were returned via email or post within a few days. The majority of tests studied cost less than 45.

According to the American Food and Drug Administration, caution is advised when consumers are buying self-tests on line. "Although many good home-use tests are available online, others may not work and may even be harmful. If you think that you have a medical condition or disease, see your doctor." Here are examples of some of the home tests available to order online.

Osteoporosis Cost: 64 to £73 What is it? Osteoporosis is a disease which affects the bones, causing them to become weak and more likely to fracture and break. One in four Irish women suffers but the condition also affects men.

How does the test work? When bones break down, compounds are released so the test involves sending a urine sample away for laboratory examination.

Should I buy it? The Irish Osteoporosis Society says that this is not a recommended diagnostic tool and that a bone density scan, called a Dual Energy X-ray Absorptiometry or DEXA scan, available at a number of units around the country, is the only reliable means of determining whether or not you have osteoporosis.

Menopause Cost: 3- 21 What is it: Also known as "the change of life", the menopause is the time when the ovaries stop producing the hormone estrogen and a woman stops having menstrual periods. Menopause marks the end of a woman's childbearing years.

How does the test work? The test measures follicle-stimulating hormone or FSH in urine. This hormone is produced by the pituitary gland and production of it increases each month in order to stimulate the ovaries to produce eggs. These levels also increase when a woman is in menopause but while the tests will identify the presence of FSH, it is not necessarily a reliable indicator of menopause as the results may be affected by the time of day the urine sample was collected, hormonal drugs such as HRT and the pill, and how much water has been consumed before the test.

Should I buy it? The US Food and Drug Administration has the following to say: "Do not stop taking contraceptives based on the results of these tests because they are not foolproof and you could become pregnant. You should not assume that a negative test means you have not reached menopause, there could be other reasons for the negative result. You should always discuss your symptoms and your test results with your doctor."

Genetic testing Cost: 223- 890 What is it? There are many home tests available which are designed to examine genes and DNA in order to discover if any predispositions to particular diseases or disorders exist.

How does the test work? A blood sample or swab from inside the cheek is sent to a laboratory for analysis.

Should I buy it? No, because these tests do not provide any insight into other factors which may affect genes, such as environmental factors and medical history. "At-home genetic tests have risks. Consumers are vulnerable to being misled by unproven or invalid tests.

Without guidance, they may make important decisions about treatment or prevention based on inaccurate, incomplete, or misunderstood information, " says the US National Library of Medicine.

Cholesterol Cost: 4.50 to 111 What is it? Cholesterol is the fat component in the blood. Excessive levels can lead to heart disease and stroke. Some research advises everyone over the age of 20 to be tested every five years.

How does the test work? Most tests provide a lance which is used to prick the finger. A drop of blood is then place on a piece of treated paper that changes colour according to cholesterol levels. A lance is usually provided and you prick your finger to get a drop of blood, which is put on to a piece of treated paper that changes colour according to the level of cholesterol.

Should I buy it? This test is generally accurate, provided you follow the directions carefully. If your cholesterol is higher than 200mg/dL, seek medical advice immediately.

HIV Cost: 13 to £17 What is it? Human immunodeficiency virus, the virus that causes Aids.

How does the test work? The test looks for antibodies to HIV in the blood, as these can be a sign of infection. Other tests look for the virus in oral fluids.

Should I buy it? The US Food and Drug Administration recounts the following story as a means of pointing out these tests' potential for inaccuracy. "Sally was afraid that she had been exposed to HIV. She decided to purchase her HIV test from an internet source. She took the test and was distraught to find that the result was positive. After several weeks, she went to her doctor, who used a more sophisticated method . . . and the result was negative. Sally did not have HIV."

Additional reporting by Claire O'Mahony

BUYING SELF TEST KITS

>> Avoid tests that promise to test for more than one disease.

>> Be wary of any websites claiming new or miracle cures.

>> Seek your doctor's advice about any tests you intend to take.

>> If you do suspect you have a medical condition, your doctor really should be your first port of call and not the internet.

>> Avoid websites with no telephone number.