False positive reporting of Hirschsprung's disease in Alaska: an evaluation of Hirschsprung's disease surveillance, birth years 1996-2007.

BACKGROUND: Hirschsprung's disease (HSCR) is a potentially fatal congenital intestinal obstruction syndrome. For birth years 1996-2002, reported HSCR prevalence in Alaska was approximately six times higher than the national estimate of two per 10,000 live births. In 2008 we completed a case verification study of HSCR reported to the Alaska Birth Defects Registry (ABDR) to verify prevalence and evaluate sensitivity and predictive value of HSCR surveillance.
METHODS: We abstracted medical records for children reported with HSCR who were born in 1996-2007 and matched to an Alaska birth certificate. We categorized reports as confirmed, ruled out, or inconclusive. ABDR sensitivity was validated by cross-referencing hospital discharge data with confirmed HSCR cases.
RESULTS: Overall sensitivity of the ABDR was 94.4%, and positive predictive value (PPV) was 31.1%. Following case verification, HSCR prevalence was three per 10,000 live births statewide and 5.6 and 2.1 per 10,000 live births for Alaska Natives and non-Natives, respectively. Positive predictive value was twice as high for the Alaska Native population as the non-Native population.
CONCLUSIONS: Multiple-source passive surveillance methodology resulted in high sensitivity for HSCR ascertainment; however, case verification was required to rule out false-positive reports, which obscured the true distribution of Alaska Native versus non-Native HSCR cases.