Investigations
1st investigations to order
FBC
Test
In the acute stage, a mild to moderate normochromic anaemia is observed, along with an elevated white blood cell count with left shift.
During the subacute stage, thrombocytosis is often observed.
Result
anaemia, leukocytosis, and thrombocytosis
erythrocyte sedimentation rate (ESR)
Test
During the acute stage, many acute-phase reactant markers, such as ESR, CRP, and serum ferritin, are significantly raised. ESR tends to return to normal levels at the end of the subacute phase towards the convalescent phase.[42]
Result
raised, but should not be used to determine response; intravenous immunoglobulin (IVIG) has been shown to increase ESR levels
serum CRP
Test
During the acute stage, many acute-phase reactant markers, such as erythrocyte sedimentation rate, CRP, and serum ferritin, are significantly raised. CRP levels normalise quicker than other biomarkers. CRP is used to guide management decisions.
Result
raised
echocardiogram
Test
European SHARE guidelines and the American Heat Association (AHA) recommend that an echocardiogram should be performed at diagnosis, but obtaining this should not delay initiation of treatment.[1][13][28] The American College of Rheumatology also strongly recommends obtaining an echocardiogram with coronary artery measurements without delay for children with suspected incomplete Kawasaki disease (KD) and fever.[32]
Echocardiography is crucial in management of KD to identify coronary artery abnormalities. During the acute stage, a baseline echocardiogram is important to rule these out and seek evidence of myocarditis, valvulitis, or pericardial effusion. Diffuse dilation of coronary lumina can be observed in 50% of untreated patients by the tenth day of illness.
Be aware that in the first week of illness, the echocardiogram is typically normal and does not rule out the diagnosis.[1][28] If the echocardiographic findings are abnormal at any stage in the course of the illness, refer the patient to a paediatric cardiologist for a complete cardiac work-up and follow-up care.
SHARE and AHA guidelines recommend routinely repeating echocardiogram 1-2 weeks after treatment, or sooner for high-risk patients.[1][13][28] For patients with high-risk features (age <6 months, Z score ≥2.5 on echocardiogram at diagnosis), the AHA recommends performing echocardiography at least every 2-3 days (or at a frequency advised by a cardiologist) to assess for worsening dilation, which may prompt further intensification of therapy. Keep the patient hospitalised and continue to repeat echocardiogram (and assess treatment) until luminal dimensions have stopped progressing.[28] For patients with expanding large or giant aneurysms, perform echocardiography at least every 2-3 days while dimensions are expanding rapidly, at least once weekly in the first 45 days of illness (unless aneurysm size has remodeled to moderate or small range), and then monthly until the third month after illness onset.[28]
For patients with a normal echocardiogram at diagnosis, evidence suggests the risk of developing coronary artery changes is extremely low in patients who respond to therapy and have a normal echocardiogram 1-2 weeks after discharge.[28] However, if coronary artery imaging is suboptimal or laboratory markers of inflammation are abnormal at 1-2 week follow-up, the AHA guideline recommends considering repeat follow-up at 4-6 weeks.[28] The European SHARE guidelines recommend an echocardiogram at 6-8 weeks after disease onset for all patients, and at least weekly in patients with or ongoing inflammation to monitor for cardiac sequelae.[13] In those with coronary abnormalities on initial echocardiogram, SHARE recommend a repeat echocardiogram at least weekly to ensure stabilisation.[13] In the longer term, SHARE recommend monitoring echocardiography every 3-6 months in children with coronary artery aneurysms, depending on their severity.[13] The AHA guidelines include a stratification system for long-term follow-up and management based primarily on maximal coronary artery luminal dimensions, normalised as Z scores; it takes into account both past and current coronary involvement to categorise patients by their risk level for development of myocardial ischaemia.[1][28]
Result
signs of coronary abnormalities during acute stage: left anterior descending coronary artery or right coronary artery Z score ≥2.5; coronary artery aneurysm seen; three or more other suggestive features, including decreased left ventricular function, mitral regurgitation, pericardial effusion, or Z scores in left anterior descending coronary artery or right coronary artery of 2.0 to 2.5
serum LFTs
Test
Icteric and anicteric hepatitis can develop, with mild elevations in aminotransferase values observed in 40% of patients.
Raised alanine aminotransferase levels can indicate a more serious course.
Bilirubin levels are raised in 10% of patients.
Result
raised liver enzymes; low level of albumin
urinalysis
Test
Will show a mild to moderate sterile pyuria of urethral origin in 50% of patients.
If urinalysis is abnormal, a culture should be performed to rule out urinary tract infection.
Result
sterile pyuria
electrocardiogram
Test
European SHARE guidelines and the American Heart Association (AHA) recommend that an ECG should be performed at diagnosis, but obtaining this should not delay initiation of treatment.[1][13][28]
Needs to be obtained to evaluate for various conduction abnormalities. Children with Kawasaki disease (KD) may also have acute infarction.
Tachycardia, a prolonged PR interval, ST-T wave changes, and a decreased voltage of R waves may indicate myocarditis. Q wave or ST-T wave changes may indicate a myocardial infarction. Bifid T waves were observed in 24% and 27% of patients in two independent cohorts of patients with acute KD.[36] SHARE and AHA guidelines recommend routinely repeating ECG 1-2 weeks after treatment, or sooner for high-risk patients.[1][13][28]
The European SHARE guidelines recommend an ECG at least weekly in patients with ongoing inflammation to monitor for cardiac sequelae.[13]
In the longer term, SHARE recommend repeating ECG every 3-6 months in children with coronary artery aneurysms, depending on their severity.[13] The AHA guidelines include a stratification system for long-term follow-up and management based primarily on maximal coronary artery luminal dimensions, normalised as Z scores; it takes into account both past and current coronary involvement to categorise patients by their risk level for development of myocardial ischaemia.[1][28]
Result
conduction abnormalities and/or myocardial infarction
Investigations to consider
CXR
Test
Looks for cardiomegaly in the case of pericarditis, myocarditis, or subclinical pneumonitis.
Should be performed to assess baseline findings and to confirm any clinical suspicion of congestive heart failure.
Result
cardiomegaly or, more rarely, pneumonitis
ultrasonography of the gallbladder
Test
May be necessary if liver or gallbladder dysfunction is suspected.
Result
hydrops of the gallbladder in some patients
ultrasonography of the testes
Test
In case of testicular involvement in males, a scrotal sonogram to evaluate for epididymitis should be performed. Epididymitis is an inflammatory process that can occur in various vasculitides and affects boys aged 9 to 14 years. It can be observed in younger boys with IgA vasculitis and Kawasaki disease.
Result
epididymitis in males with testicular involvement
lumbar puncture
Test
May be needed in patients who present with high fever and nuchal rigidity.
Some patients with Kawasaki disease may have aseptic meningitis.
Aseptic meningitis could be one of the adverse effects of intravenous immunoglobulin (IVIG) treatment.
Result
aseptic meningitis in some patients
computed tomography angiography
Test
May be recommended by cardiology to further assess coronary aneurysms, especially in the context of unclear findings on echocardiography or in the presence of giant aneurysms.[28]
Computed tomography angiography (CTA) is typically the preferred modality for detection and long-term follow-up of coronary artery aneurysms, but the choice of imaging modality depends on the clinical context and local availability.[28][37] For patients with rapidly expanding giant coronary artery aneurysms during hospitalisation, performing CTA immediately prior to discharge can help map the extent of the aneurysms in the short term.[28] CTA can be performed in children with relatively low radiation exposure if obtained at an institution with proper expertise.
Result
coronary dilations or aneurysms
magnetic resonance angiography (MRA)
Test
May be recommended by cardiology to further assess coronary aneurysms, especially in the context of unclear findings on echocardiography or in the presence of giant aneurysms.[28]
Free-breathing 3-dimensional coronary MRA may accurately define coronary artery aneurysms in patients with Kawasaki disease. Cardiovascular magnetic resonance is useful for demonstrating coronary artery aneurysms and other coronary pathology.[43]
MRA does not involve radiation exposure, but scanning times are typically longer, and it is less sensitive, than computed tomography angiography for identification of stenoses, calcifications, ectasia, and distal coronary artery disease.[28][37][38] MRA may be challenging to perform in young children <15 kg in weight.
Result
coronary dilations or aneurysms
cardiac catheterisation and angiography
Test
May be recommended by cardiology to further assess coronary aneurysms, especially in the context of unclear findings on echocardiography or in the presence of giant aneurysms.[28] Invasive angiography is rarely required given the widespread availability of computed tomography angiography, but it may be used in certain scenarios (e.g., when non-invasive imaging results are equivocal or when percutaneous revascularisation is being considered in the setting of acute myocardial infarction, angina, or inducible ischaemia stress testing).[28][39]
Care should be taken when considering invasive angiography in the presence of ongoing systemic inflammation since rates of complication (such as catheter-related myocardial infarction) may be higher.
Cardiac catheterisation with angiography may be challenging to perform in young children <15 kg in weight.
Result
coronary artery aneurysms
Emerging tests
natriuretic peptide tests
Test
Elevated N-terminal pro-brain natriuretic peptide (NT-proBNP) may be present in Kawasaki disease.[40] However, these do not automatically confirm the diagnosis as they may be associated with a wide variety of cardiac and non-cardiac causes.
Result
elevated levels of natriuretic peptides
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