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.