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An Evaluation of Hospitalizations for Kawasaki Syndrome in Georgia
Robert V. Gibbons, MD;
Umesh D. Parashar, MBBS;
Robert C. Holman, MS;
Ermias D. Belay, MD;
Ryan A. Maddox, MPH;
Kenneth E. Powell, MD;
Lawrence B. Schonberger, MD
Arch Pediatr Adolesc Med. 2002;156:492-496.
ABSTRACT
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Objective To evaluate and describe the epidemiologic characteristics of Kawasaki
syndrome (KS) hospitalizations in Georgia.
Design We reviewed hospital discharge data and corresponding medical records
for Georgian patients discharged with a KS diagnosis during 1997 and 1998.
Results During the study period, 233 KS hospital discharges were recorded in
Georgia; 177 (76%) were for children younger than 5 years. Twenty-one (9%)
of 233 of the hospital discharges represented multiple hospitalizations. Medical
records for 211 KS discharges (91%), representing 197 patients (93%), were
reviewed. For those 189 patients whose medical records were reviewed and had
sufficient information, 139 (74%) either had a documented illness that met
the Centers for Disease Control and Prevention (CDC) definition for KS (n
= 135) or had coronary artery abnormalities without meeting the CDC definition
for KS (atypical KS; n = 4). Eight patients had only a history of KS. Excluding
multiple hospitalizations and patients with only a history of KS, 158 hospitalizations
were for patients younger than 5 years (14.0 per 100 000 children); 110
of these patients met the KS or atypical KS definition (9.8 per 100 000
children).
Conclusions Hospital discharge data are useful for KS surveillance. However, analysis
of hospital discharge data may slightly overestimate the KS hospitalization
rates because some discharges may represent multiple hospitalizations or hospitalizations
of patients with only a history of KS. The incidence and epidemiology of KS
in Georgia are consistent with findings from other continental US studies.
Physicians should exercise their best clinical judgment in identifying and
treating patients with KS who may not meet standard case definitions.
INTRODUCTION
KAWASAKI SYNDROME (KS), an illness of unknown origin, occurs worldwide,
with the highest incidence in Japan.1 In the
United States and Japan, KS is the leading cause of acquired heart disease
among children.2 The most serious cardiac complications
of KS are coronary artery abnormalities (CAA).3
Timely treatment of patients with KS with intravenous immunoglobulin (IVIG)
and aspirin has been reported to reduce the rate of occurrence of CAA.1-3
The epidemiologic characteristics of KS in the United States have been
described in previous studies.4-11
Some studies have analyzed hospital discharge data, and several of these studies
have compared physician diagnosis of KS with a specific KS case definition.5, 7, 11 A recent report11 from a large, pediatric hospital in Utah showed that
the proportion of patients diagnosed as having KS that did not meet a specific
case definition increased from 27% during 1991 to 1994 to 45% during 1995
to 1997, indicating a need for a timely reevaluation of this issue among patients
from a variety of hospitals in different settings.
In this study, we examined patients discharged with a diagnosis of KS
using the Georgia hospital discharge data for 1997 and 1998. We reviewed the
patients' medical records to compare their clinical signs and symptoms with
the Centers for Disease Control and Prevention (CDC) case definition for KS12 and to evaluate the usefulness of hospital discharge
records for KS surveillance.
METHODS
Hospital discharge data for KS hospitalizations in Georgia during 1997
and 1998 were obtained from the Division of Public Health, Georgia Department
of Human Resources, Atlanta. A KS hospitalization was defined as one with
the International Classification of Diseases, Ninth Revision,
Clinical Modification (ICD-9-CM) discharge
code 446.1 listed as one of the diagnoses on the discharge record.13 The county of residence was used to examine the geographic
distribution and define residence as urban (metropolitan statistical areas)
or nonurban.14
Hospital discharge records for KS were examined, and patients as the
unit of observation were identified for further study. Patients with multiple
hospitalizations were identified by the medical record number and by using
an algorithm based on the date of birth, sex, and county of residence and
further assessed during the medical record review. For patients with multiple
KS hospitalizations within 1 year, their hospitalizations were considered
as part of the same episode of KS; the length of stay and the signs and symptoms
were combined for analysis.
The hospitals that reported having discharged patients with a diagnosis
of KS during the study period were contacted by letter and telephone to arrange
for review of medical records. These medical records were then reviewed, and
information was obtained on demographics, illness characteristics, treatment
with IVIG, and the presence of CAA. The Institutional Review Board of the
Georgia Department of Human Resources approved this study.
Patients were classified on the basis of the CDC KS case definition.12 This case definition includes the presence of fever
for 5 or more days, or fever until the date of IVIG administration if it is
given before the fifth day of fever, and any 4 of the following 5 criteria:
(1) bilateral conjunctival injection, (2) oral changes (erythema of the lips
or oropharynx, strawberry tongue, or drying or fissuring of the lips), (3)
peripheral extremity changes (edema, erythema, or desquamation), (4) rash,
and (5) cervical lymphadenopathy (at least one node  1.5 cm in diameter).
Patients whose illness did not meet these criteria, but who had fever and
CAA, were classified as having atypical KS.12
The epidemiologic and clinical characteristics of patients whose illness
met the CDC criteria for KS or atypical KS were compared with those whose
illness did not. Categorical variables were compared using the  2 or Fisher exact test (2-tailed), as appropriate, and continuous variables
were compared by using the Wilcoxon rank sum test.15
Average annual KS hospitalization and incidence rates (per 100 000 children)
for children younger than 5 years in Georgia were calculated by using the
Georgia state census population.16-17
Risk ratios with 95% confidence intervals were calculated using Poisson regression
analysis.18
RESULTS
During 1997 and 1998, 233 hospital discharges for KS in Georgia were
identified; in 214 (92%) of these discharges, KS was listed as the primary
diagnosis. The KS hospitalization rate for children younger than 5 years (n
= 177 hospitalizations) was 15.7 per 100 000 children. These 233 discharges
represented 212 patients and were from 40 different hospitals in Georgia (Figure 1A); 21 (9%) of the 233 discharges
were for multiple hospitalizations of 18 patients (8%). Of these 18 patients,
15 (83%) were readmitted or transferred within 1 month of the previous discharge;
records of 2 of the remaining 3 patients were reviewed, and only 1 met the
KS case definition. Medical records for 211 KS discharges (91%), representing
197 patients (93%), were reviewed. Most patients with KS (75%) were hospitalized
in urban hospitals. Eight hospitals that reported discharging 9 patients with
KS did not participate in the study.
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Figure 1. A, Flowchart of study of Kawasaki
syndrome (KS) hospitalizations, Georgia, 1997-1998. B, Flowchart of study
of the medical records of patients with physician-diagnosed KS, Georgia, 1997-1998.
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Sufficient data to assess the KS case status were available for 189
of the 197 patients whose medical records were reviewed (Table 1). The case definition for KS (n = 135) or atypical KS (n
= 4) was fulfilled by 139 (74%) of the 189 patients (Figure 1B). Of the 135 patients whose illness met the KS case definition,
53 met all the criteria, 19 met at least 4 criteria with the status of 1 criterion
unknown, and 63 met 4 of 5 criteria. Eight (4% of the total patients) of the
50 patients who did not meet the case definition for KS or atypical KS had
only a history of KS reported at the time of hospitalization; 5 of these 8
patients were the only patients 18 years or older, and 2 patients were younger
than 5 years. Therefore, 139 (76%) of 184 patients met the KS case definition
when restricting to patients younger than 18 years and 139 (77%) of 181 when
excluding patients with only a history of KS. Excluding multiple hospitalizations
(n = 17) and those with only a history of KS (n = 2) for children younger
than 5 years, there were 158 patients younger than 5 years.
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Table 1. Number of Patients Discharged With a Diagnosis of Kawasaki
Syndrome (KS) by Criteria Status, Georgia, 1997 and 1998
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Age, sex, urban residence, and characteristics of treatment received
did not differ significantly between those patients whose illnesses met and
did not meet the KS definition (Table 2). Intravenous immunoglobulin was given to 97% of those whose illness
met the KS case definition, 90% of those whose illness did not meet the definition,
and 75% of those with insufficient data to classify. Among those patients
whose illness met the KS case definition, the proportions for individual symptom
criteria were as follows: oral mucosal changes, 98%; rash, 97%; conjunctival
injection, 94%; extremity changes, 86%; and cervical adenopathy, 58%. For
those patients whose illness did not meet the case definition, both extremity
changes (29%) and cervical adenopathy (21%) were infrequently reported. Among
patients younger than 18 years, the proportions of patients meeting the KS
case definition did not differ between those with a primary diagnosis of KS
and those with a secondary KS diagnosis (132 [76%] of 174 and 7 [70%] of 10,
respectively).
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Table 2. Characteristics of Patients With a Diagnosis of Kawasaki Syndrome
(KS) by Case Definition Status, Georgia, 1997 and 1998
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At least one echocardiogram report was available for review for 122
(90%) of the 135 patients whose illness met the KS case definition, all 4
patients with atypical KS, and 30 (71%) of the 42 patients who did not meet
the criteria. Fifteen (12%) of the 122 patients had evidence of CAA. Seven
of these 15 patients had an echocardiogram positive for CAA within 10 days
of KS onset; the remaining 8 patients did not have an echocardiogram within
10 days of onset. All of those 15 patients with CAA had dilations of the arteries,
and 4 also had aneurysms. All patients with CAA received IVIG treatment; however,
8 (53%) of 15 of these patients received it within 10 days of illness onset
compared with 97 (94%) of 103 patients without CAA who had a known date of
IVIG treatment (P<.001). For the 7 patients with
CAA and delayed IVIG treatment, the treatment was administered a median of
15 days after illness onset.
Most hospitalizations (79%) for patients whose illness met the KS or
atypical KS case definition were for children younger than 5 years (Table 2, Figure 2). Hospitalizations occurred year-round, with a peak during
May and June (26%). The geographic distribution of KS cases was consistent
with the distribution of the population of children younger than 5 years in
Georgia. No deaths were reported for patients with KS.
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Figure 2. A, Age distribution by year of
patients whose illness met the Kawasaki syndrome (KS) case definition, Georgia,
1997-1998 (n = 139). B, Age distribution by month of patients younger than
5 years whose illness met the KS case definition, Georgia, 1997-1998 (n =
107).
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For children younger than 5 years, the average annual incidence for
patients with physician-diagnosed KS was 14.0 per 100 000 children; for
those children whose illness met the criteria for KS or atypical KS, the average
annual incidence was 9.8 per 100 000 children (Table 3). Although a higher proportion of boys had KS than girls,
the difference was not significant. The incidence between patients younger
than 1 year and those 1 to 4 years old did not differ. The incidence for Asian
children was highest and was at least 4 times greater than that for white
children. The incidence for Asian children was almost twice that for black
children, although it was not significantly higher.
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Table 3. Kawasaki Syndrome (KS) Incidence for Characteristics of Children
Younger Than 5 Years, Georgia, 1997 and 1998*
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COMMENT
In this statewide review of medical records of Georgian children hospitalized
with KS, 74% of patients with an ICD-9-CM code for
KS listed on their discharge record met the CDC case definition for KS or
atypical KS. This proportion is comparable to the 73% reported by Dykewicz
et al,7 whose study was based on hospital discharge
data and other sources of data. Exclusion of patients with a history of KS
indicated that 77% of physician-diagnosed KS cases met the KS case definition.
This percentage is greater than the 64% reported in a similar study recently
published by Witt et al11; however, it may
reflect the difference in the KS case definitions used. Witt and colleagues
used a case definition requiring fever for 5 days or more regardless of the
timing of IVIG treatment, and early treatment could reduce the duration of
fever.
Our data should not be interpreted to imply that the patients not meeting
the CDC case definition did not have KS, because several factors other than
misdiagnosis of an illness similar to KS could account for this discrepancy.
First, increased awareness of KS and its complications may lead to reluctance
of clinicians to withhold effective IVIG therapy for patients whose illnesses
do not meet the KS diagnostic criteria. The administration of IVIG early in
the course of the disease may also prevent the appearance of the typical clinical
signs of KS. Second, incomplete documentation of KS clinical signs may have
affected our findings that relied exclusively on retrospective review of medical
records. Notably, the 2 criteria reported least frequently in patients not
meeting the case definition—cervical adenopathy and extremity changes—may
have been less rigorously documented. Third, some patients with KS may have
an atypical presentation without exhibiting the full range of signs and symptoms
of the disease. Such patients may actually benefit from early diagnosis and
treatment to reduce the likelihood of cardiac complications. Physicians should
exercise their best clinical judgment in identifying and treating these patients.
Two findings of our review are relevant for reducing the likelihood
of overestimating KS incidence in future studies that use hospital discharge
data. First, multiple hospitalizations, resulting from transfer to a different
facility or rehospitalization for the same KS episode, may have occurred for
18 patients. The use of a unique patient identifier, if available, or an algorithm
based on variables such as age, sex, and dates of hospitalization might allow
detection of these multiple hospitalizations without review of the medical
records. Second, 8 patients had only a history of KS and were hospitalized
for an unrelated illness; 5 of these patients were 18 years or older. None
of the cases that met the KS definition were 18 years or older. Therefore,
the specificity of KS surveillance based on hospital discharge data could
be improved by restricting the analysis to patients younger than 18 years.
Other factors that may affect the incidence in a statewide hospitalization
study, but may not be easily accounted for, include the possibility of diagnostic
miscoding, nonhospitalization for KS, and patients seeking treatment in another
state.
The estimated true annual incidence of hospitalized cases of KS in Georgia
during 1997 to 1998 was probably between 11 and 14 cases per 100 000
children younger than 5 years. The minimum estimate is derived from the documented
KS incidence of 9.8 per 100 000 children and adjusted for the proportion
of KS hospital discharges of patients with the case status unknown. The maximum
estimate assumes that each patient's diagnosis of KS is accurate regardless
of some patients' illnesses not meeting the case definition. The estimate
of the true annual KS incidence is within the range of those reported in other
studies in the continental United States (4.0-19.1 per 100 000 children
younger than 5 years).4-7,9-10,19-20
The epidemiologic characteristics of children hospitalized with KS in
Georgia are similar to those reported in other US studies.5-9,12, 19-23
The highest incidence of KS in Georgia was among Asian children, followed
by black and white children, as reported in previous studies. Seven of the
15 patients with KS with CAA received their IVIG treatment 10 days or more
after illness onset, although they met the case definition for KS. The reasons
for delayed IVIG administration in these patients are unclear. Nevertheless,
every effort should continue to be made to identify and treat patients as
early as possible to reduce the likelihood of cardiac complications.
In conclusion, the findings of this study indicate that hospital discharge
data are useful for surveillance of KS. The accuracy of hospital discharge
data can be increased by excluding multiple hospitalizations for the same
person and by limiting the analysis to patients younger than 18 years. Because
the KS clinical signs lack specificity, an accurate diagnosis of KS in some
patients and determination of its true incidence may pose challenges to both
clinicians and epidemiologists. Overcoming these challenges may largely depend
on the identification of the etiologic agent and development of a specific
diagnostic tool.4 In the meantime, physicians
should exercise their best clinical judgment in identifying and treating patients
with KS who may not meet the standard case definition to reduce the likelihood
of cardiac complications.
| What This Study Adds
Kawasaki syndrome, an illness of unknown origin, is the leading cause
of acquired heart disease among children. The study compares the clinical
signs and symptoms of patients with KS identified in hospital discharge data
with the CDC case definition and describes the epidemiologic characteristics
of these patients. The findings indicate that 77% of patients with physician-diagnosed
KS met the case definition. Hospital discharge data are useful for surveillance
of KS.
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AUTHOR INFORMATION
Accepted for publication January 25, 2002.
This study was supported in part by an appointment to the Research Participation
Program at the CDC, National Center for Infectious Diseases, Division of Viral
and Rickettsial Diseases (Atlanta, Ga), administered by the Oak Ridge Institute
for Science and Education (Oak Ridge, Tenn) through an interagency agreement
between the US Department of Energy (Washington, DC) and the CDC.
We thank the personnel in participating hospitals for their assistance
and cooperation. The authors also thank John O'Connor, MS, for editorial assistance.
Corresponding author and reprints: Robert C. Holman, MS, Centers
for Disease Control and Prevention, Mail Stop A-39, 1600 Clifton Rd NE, Atlanta,
GA 30333.
From the Division of Viral and Rickettsial Diseases, National Center
for Infectious Diseases (Drs Gibbons, Parashar, Belay, and Schonberger and
Messrs Holman and Maddox), and Epidemic Intelligence Service (Dr Gibbons),
Centers for Disease Control and Prevention, and the Epidemiology Branch, Division
of Public Health, Georgia Department of Human Resources (Drs Parashar and
Powell), Atlanta. Dr Gibbons is currently with the Walter Reed Army Institute
of Research, Silver Spring, Md.
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