National estimates of Kawasaki disease (KD) incidence often do not include incomplete cases (diagnosed based on only laboratory or echocardiographic criteria), and/or they rely on retrospective case reports and data registries where underreporting is known to be a problem.
We conducted a prospective nationwide KD surveillance study in children younger than 5 years through the hospital-based German Pediatric Surveillance Unit (ESPED). We accounted for underreporting through applying capture–recapture methodology in 2 federal states using hospital discharge records with KD International Statistical Classification of Diseases and Related Health Problems 10th revision code (ie, M30.3). KD diagnosis (complete and incomplete) was established according to the American Heart Association criteria, 2004.
Incidence of KD, corrected for underreporting, was 7.2 of 100,000 in children younger than 5 years in Germany. Underreporting to ESPED was estimated at 37%–44%. Overall, 315 validated KD cases were reported. Of the 64 (20%) incomplete cases, 58% (37/64) were detected through echocardiographic findings and 42% (27/64) through laboratory criteria alone. Incomplete cases were younger than complete cases (1.2 vs. 2.0 years, P = 0.0001) and had more coronary aneurysms (43% vs. 11%, P = 0.0001).
A substantial number of incomplete KD cases were diagnosed based on the laboratory and echocardiographic criteria only. This was particularly the case in relation to infants younger than 1 year—an age group known to have an increased risk of developing coronary aneurysms. In addition, we found a high rate of underreporting to national Pediatric Surveillance Units. We suggest that improved surveillance and development of better diagnostic tests remain a high priority.