Learning about medical tests

Medical tests and procedures are integral parts of the monitoring of HIV disease and of the investigation and treatment of symptoms. Before any test is carried out, it is important to know the reason for the test, a description of what it involves, and why the result will be useful. Some tests may have specific instructions, such as needing to be done on an empty stomach or at a particular time of day. It is part of good medical practice for doctors to ensure that this information is discussed and that patients understand and agree to the procedures.

Many blood tests will have a 'normal' value or give a 'standard reference range'. Keep in mind that 'normal' can sometimes vary by age, weight, gender, time of day the test is performed, and test method. Values and ranges often differ between different hospitals and labs. A lab report will give the value or specific reference range for that laboratory (reflecting the technique/technology used) and for the individual being tested.

If a value is out of the normal range, it just indicates that further investigation is needed. For example a ‘normal’ heart rate, based on millions of readings, is about 70 beats a minute. If someone has 60 beats a minute, or even 50 beats, it could just mean that person is a good athlete and their heart works very efficiently. Results always need to be correlated to the individual and considered within the context of other information.  

A urinalysis can show straight away whether glucose is present. A swab for strep infection gives a straightforward negative or positive result. However, other tests can just give part of an answer that then needs to fit with other factors. These factors may range from the individual’s medical history, present health status, current medications, normal diet, and other test results, through to what else is going on that day and what was eaten for breakfast.

If test results are ‘abnormal’ or out of the reference range, the first step may be to repeat the test. Depending on the significance of the test result, waiting and watching for further change is all that may need to be done. Sometimes, it is only through discussion that the reasons for an abnormal test can be worked out. 

Some tests do not provide a range, but will give a cut-off value. Examples of this are a PSA test (prostate specific antigen) or cholesterol. A result over or under the cut-off point, depending on the test, usually indicates that a clinical decision point has been reached.

The following list details some of the more common tests and procedures that are ordered for persons with HIV infection, resources allowing. It is representative, not exhaustive, in scope. 

For many individuals, a blood draw is not an issue. If you are not one of those people, the following tips might help in getting through the procedure with minimal stress and discomfort.

• Ask for a 'butterfly' or paediatric needle.
• Rub or tap the area where the draw will be done.
• Establish a slow and steady breathing pattern and then quietly blow out as you feel the needle being placed.
• Just as the needle is being placed, pinch another part of your body, for instance, the outer thigh.
• Close your eyes and visualise a colour or scene.
• If you think you may faint, ask to lie down for the test.
• Check with your doctor about the possibility of using lidocaine cream (Emla) to numb the area ahead of time. This will need to be done about 30 minutes before the test. Ask about this when your doctor gives you the lab order. Not every lab has lidocaine cream on hand and it is, in many countries, a prescription drug that will need to be picked up ahead of time.