Blood tests are a ubiquitous part of general practice, and every day, thousands of doctors, nurses and phlebotomists take blood samples from patients. Most of these tests will turn out to be normal. They will have been taken for many different reasons - not only to make, confirm or exclude a diagnosis, but also to reassure both doctor and patient.

When patients then contact their practice for the results, they are frequently told: ‘Your blood test was normal.' I just wonder how many of us really consider how patients might interpret these simple words.

I have known patients ask after a blood test if they can be told what their blood group is, and are surprised to discover that this was not tested. Many of our patients appear to believe that a blood test will test for everything - a not unreasonable expectation in these high-tech days.

What does this potential misinterpretation really mean? If a doctor performs a blood test to measure the haemoglobin level, and simply informs the patient that his or her blood test was normal, might not the patient assume that everything - including maybe even the HIV status - was normal? If so, the public health implications of blood testing are enormous.

There has been remarkably little research into patients' understanding of blood test results. However, a study looking at women's understanding of cervical smear results showed that most women found it difficult to get the information they required from doctors because they were confused by what they were told and felt unable to ask questions in the consultation. 

While most of us now involve our patients much more closely in decision making, it seems likely that a combination of the inherent perceived power differentials of medical practice and our constant time pressures frequently make it difficult for us to give all the detailed information that patients might really need. While dealing with test results is an everyday occurrence for doctors, I suspect that it can be both alarming and confusing for patients.

Moreover, most of us are likely to think that giving a patient a normal test result will be reassuring. However, I was intrigued to find that this view was strongly challenged by one Australian study into echocardiography which found that patients were frequently not reassured at all by a normal result, and the authors suggest that using investigations in the belief that a normal result will reassure patients may well be unsuccessful. Merely asserting that there is nothing wrong can seem to deny the reality of the patient's concern. ‘You say I'm normal, and I feel lousy.... Don't you believe me? Is the test wrong?'

However, another branch of healthcare may have shown us the way forward. Last week I took my ageing Labrador to the vets for a check up. He's happy enough, but with two titanium knees and a recent history of volvulus, we can't be too careful. In the waiting room,

I saw a display of leaflets explaining in remarkable detail precisely what tests are being carried out, and what the results mean. I've rarely seen such information readily available in general practices, or even in outpatient clinics. I suspect good leaflets do exist (maybe you use them) but in general such information is rarely shared with human patients in any detail.

I'll try to be more precise when explaining results in future.