Lab results change in consistent ways during the course of Kawasaki disease

Children with Kawasaki disease show a pattern of changing laboratory test results as the disease runs its course, according to a study in the December issue of The Pediatric Infectious Disease Journal. The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health.

"Understanding the dynamic changes in laboratory values can assist physicians in using laboratory criteria to diagnose Kawasaki disease following [current] guidelines," according to the new research, led by Dr Adriana H. Tremoulet of University of California, San Diego. The patterns may also aid in monitoring patient recovery during treatment for Kawasaki disease.

The researchers analyzed laboratory test results in 380 consecutive children treated for Kawasaki disease between 2002 and 2009. Kawasaki disease is the leading cause of acquired (that is, not congenital) heart disease in children, causing widespread inflammation of the blood vessels.

Kawasaki disease is a rare but a serious condition that can be complicated by the development of coronary artery aneurysms—abnormal widening of the arteries supplying blood to the heart muscle. Fortunately, if Kawasaki disease is recognized and treated with intravenous immune globulin (IVIG), most children will recover without complications.

Dr Tremoulet and colleagues analyzed changes in blood test results over three time periods:
•Acute illness, days 2 to 10, before treatment with IVIG.
•Subacute illness, days 11 to 21.
•Convalescent illness, days 22 to 60.

Most blood test values peaked during the acute phase. This included key markers of inflammation important in making the diagnosis of Kawasaki disease: white blood cell count, erythrocyte sedimentation rate, and C-reactive protein.

However, other values continued to rise after the start of treatment. Platelets (blood cells involved in clotting) peaked in the subacute phase while lymphocytes and eosinophils (involved in immune responses) peaked during the convalescent phase.

Nine percent of the children developed coronary artery aneurysms. These children could be identified by a higher white blood cell count in the subacute phase and a higher erythrocyte sedimentation rate during the subacute and convalescent phases.

The diagnosis of Kawasaki disease can be challenging to make, because the initial symptoms—such as fever and rash—are often non-specific. Current guidelines emphasize the role of laboratory tests, especially markers of inflammation, in diagnosing Kawasaki disease. The new study is the first to take an in-depth look at how laboratory values change over time.

The results provide new insights into how lab test results change during different phases of illness in children with Kawasaki disease, including the response to treatment. Dr Tremoulet and coauthors hope their findings will provide doctors with helpful information for making the diagnosis of Kawasaki disease, as well as in monitoring the patient's progress during recovery. They conclude, "Understanding the evolution of standard clinical laboratory test results in Kawasaki disease patients, both before and after IVIG therapy, should help physicians to calibrate their expectations of changes in laboratory values over time."