Your child will need some tests to diagnose (identify) HSP and find out whether he or she needs any treatment. Your doctor will do an examination, measure your child’s blood pressure, and do one or more urine tests. Your child may need other tests, such as blood tests, an ultrasound scan or a biopsy of his or her kidney or skin.
Examination
Your doctor will talk to you or your child about their symptoms and any medicines that he or she takes. The doctor will examine your child – for example, to look at the purpura (rash).
Your doctor or nurse will check your child’s blood pressure. This is because HSP may lead to high blood pressure (hypertension).
Urine tests
You or a nurse will need to collect some of your child’s urine in a small, clean container for a urine test. A dipstick will be dipped into the urine – this is a strip with chemical pads that change colour depending on what substances are in the urine. This shows whether there are blood cells and/or protein, which are signs of HSP with kidney involvement. The sample may also be sent to a laboratory for more accurate tests.
Blood tests
Your child may need one or more blood tests. A small amount of blood will be taken from a vein, with a needle and syringe for a blood test. A special gel or cream can be used to help your child stop feeling any pain. The blood test results can give the doctor more information, including:
- how well your child’s kidneys are working – this is called the kidney function
- about the immune system, and whether there has been a recent infection
- the level of protein in your child’s blood
- the numbers of types of blood cells and information about how the blood forms blood clots (when blood clumps together to help heal)
- the amount of other substances, including important chemicals called electrolytes.
Blood tests for HSP
Urea and creatinine are chemicals that are made in the body. They are normally removed by the kidneys into urine. In severe cases of HSP, these may build up in the blood.
The kidney function can be checked by measuring the glomerular filtration rate (GFR). The GFR is the amount of fluid the kidneys filter each minute. It can be estimated by measuring the amount of creatinine in the blood.
Infection and immune system
A blood test can check levels of immunoglobulins or antibodies – the body’s immune system makes these unique proteins to identify and kill specific germs. This gives information about whether there has been an infection, and sometimes which germ caused it.
Some children with HSP have high levels of immunoglobulin A (IgA), an antibody, in their blood. When the kidney is involved, IgA can be trapped in the glomeruli, the kidney filters.
Protein in the blood
Some children with HSP lose a lot of protein in their urine, when it is leaked through the glomeruli. This means there is less protein in their blood, especially a type of protein called albumin. Because albumin is smaller than other proteins, it is more likely to leak through the glomeruli.
Electrolytes
Electrolytes are important chemicals in the body. We need the right balance of these to stay healthy. Some important electrolytes include the following:
- sodium helps balance the amount of water in the body
- potassium is needed for the muscles, including the heart muscle, to work properly
- bicarbonate balances the amount of acid in our body, or the pH balance (also called the acid–base balance)
- phosphate is important for bones, teeth and muscles
- calcium is important for bones and teeth, helps blood to clot and also helps the muscles, including the heart muscle, to work.
Full blood count and blood clotting test
A full blood count (FBC) counts the numbers of different types of blood cells – a higher or lower level of these may be a sign of infections or other health problems.
A blood clotting test look at how the blood forms clots, when the blood clumps together – for example, when we have a cut, to stop the body losing too much blood.
Imaging tests
Some children need imaging tests (scans). These use special equipment to get images (pictures) of the inside of their body.
- Ultrasound scan – looks at the shape and size of kidneys and other parts of the urinary system. A special probe (like a stick or wand) with jelly on its tip is moved around your child’s skin. It uses sound waves to create an image on a screen. Boys who have swelling in their scrotum may also need an ultrasound scan of this part of their body.
- Chest X-ray – for children with breathing problems, chest X-ray checks for any fluid (liquid) around the lungs. Your child sits or lies still for a few seconds while a machine takes X-ray pictures.
Skin and kidney biopsy
In a biopsy, a tiny piece of a body tissue is taken from the body and examined under microscopes. Special medicines are used so your child does not feel any pain or can sleep through the procedure.
Skin biopsy
A skin biopsy can confirm whether the purpura is caused by HSP. This is rarely needed and your doctor will give you more information about this procedure.
Kidney biopsy
A kidney biopsy can find out more about the kidneys’ health. This is rarely needed, and usually for children with:
- swelling in their body (oedema) when the kidneys leak a lot of protein
- significant amounts of protein in their urine (proteinuria) for more than four weeks
- acute kidney injury – when the kidneys stop working properly over a short time.
It can take a few weeks to get the results from a biopsy.