There is no single test that can be used to confirm Kawasaki disease. Instead, your GP will diagnose your child's condition by looking at their symptoms and by carrying out a physical examination.
Fever and key symptoms
The National Institute for Health and Clinical Excellence (NICE) states that your child may have Kawasaki disease if they have a high temperature (fever) of 38C (100.4F) or above for longer than five days, and they have at least four of the following key symptoms:
- conjunctival injection in both eyes, where the whites of your child’s eyes are red and swollen
- changes to the mouth or throat, such as dry, cracked lips or a red, swollen tongue
- changes to the skin on the arms or legs, such as swelling, redness or peeling skin
- a rash
- swollen lymph nodes in the neck
For a more detailed description of these symptoms, see Symptoms of Kawasaki disease.
It is also possible for your child to be diagnosed with Kawasaki disease if they do not have four of these key symptoms. They may have an atypical (irregular) or incomplete case of Kawasaki disease.
If your child has only had a fever for four days but has four or more of the key symptoms above, they may still be diagnosed with Kawasaki disease.
Further tests
Your child may need to have some further tests to rule out any other conditions that could be causing their symptoms.
There are also a number of tests that can be carried out during the first 7-10 days of the condition to help support the diagnosis. Individually, these tests may not be conclusive, but when combined with some of the key symptoms above, they can help confirm that your child has Kawasaki disease.
White blood cells
A sample of your child’s blood will be tested to see how many infection-fighting white blood cells it contains. In over 50% of cases of Kawasaki disease, the blood contains a higher number of white blood cells than normal.
Platelet count
The number of platelets (clotting cells) in the blood may also be tested. The platelet count is usually at its highest during the second or third week of having Kawasaki disease. A platelet count may not help diagnose Kawasaki disease in the first two weeks, but it can be used to confirm the diagnosis later on.
Urine analysis
A urine sample may be tested to see whether it contains white blood cells, which could also indicate Kawasaki disease. If your child has Kawasaki disease, their urine should not contain any bacteria.
C reactive protein (CRP)
C reactive protein (CRP) is produced by the liver at the start of an infection or inflammation (swelling) in the body. The amount of CRP in the blood can be measured. An increased amount indicates inflammation or an infection.
The CRP test cannot diagnose the condition that is causing the inflammation, but it can confirm that there is a problem.
Erythrocyte sedimentation rate (ESR)
The erythrocyte sedimentation rate (ESR) is a measure of how much inflammation (swelling) there is in the body. To calculate your child’s ESR, a blood sample is placed in a test tube. The amount of time that it takes the red blood cells (the cells that transport oxygen around the body) to sink to the bottom of the tube is measured.
If the red blood cells sink faster than usual, it may mean that your child has an inflammatory condition, such as Kawasaki disease. Like a CRP test, ESR only shows whether or not there is inflammation in the body, but not what condition is causing it.
Cerebrospinal fluid (CSF)
Cerebrospinal fluid (CSF) is the fluid that surrounds the brain and spinal cord. A procedure called a lumbar puncture involves taking a sample of CSF by inserting a needle between the vertebrae (back bones) in the lower spine. The CSF can be tested for white blood cells, which could be a sign of Kawasaki disease.
Other blood tests
A sample of your child’s blood may also be tested to see what else it contains, such as:
- sodium (salt)
- proteins
- enzymes (proteins that speed up and control chemical reactions)
- lipid (fats)
If the blood contains abnormal amounts of any of these, it may be a sign of Kawasaki disease.
Heart problems
When Kawasaki disease causes complications, they usually affect the heart (see Complications of Kawasaki disease). Therefore, your child may need to have some tests to check that their heart is functioning normally, such as:
- Electrocardiogram (ECG): this measures the electrical activity of the heart using electrodes (flat metal discs) that are attached to your child’s arms, legs and chest. The ECG can detect damage to the heart or problems with the rhythm of the heart.
- Echocardiogram: this uses ultrasound (high-frequency sound waves) to produce images of the heart. This will reveal whether there are any problems with the heart’s structure or function.
During the acute phase of Kawasaki disease (weeks 1-2), several heart abnormalities may be identified. These could include:
- tachycardia (a rapid heart rate)
- pericardial effusion (a collection of fluid in the heart)
- myocarditis (inflammation of the heart muscle)
In about 30-50% of cases of Kawasaki disease, the blood vessels around the heart are widened slightly, which can cause the above heart abnormalities. In most cases, these abnormalities resolve six to eight weeks after the start of the condition, although in some people further complications can develop.
Glossary
Disease
A disease is an illness or condition that interferes with normal body functions.
Fever
A fever is when you have a high body temperature of 38C (100.4F) or over.
Lymph nodes
Lymph nodes are small oval tissues that remove unwanted bacteria and particles from the body. They are part of the immune system.
Bacteria
Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some are good for you.
Inflammation
Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.
Blood
Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
Platelet
Platelets are cells in the blood that control bleeding by plugging the broken blood vessel and helping the blood to clot.
White blood cells
White blood cells are the part of blood that fights infection and disease.
Red blood cells
Red blood cells are cells in the blood that transport oxygen around the body.
Enzymes
Enzymes are proteins that speed up and control chemical reactions in the body, such as digestion.
Heart
The heart is a muscular organ that pumps blood around the body.