title: Regional bias in birth defect prevalence rates for Arkansas: influence of incomplete ascertainment along surveillance system borders.
abstract: BACKGROUND
  As part of the continuing evaluation of the Arkansas Reproductive Health Monitoring System (ARHMS), we assessed the effects on birth defect prevalence rates introduced by incomplete case ascertainment along surveillance boundaries.
  
  
  METHODS
  Using data from ARHMS and Arkansas Vital Statistics for 1993-1998, we determined birth defect prevalence rates (per 10,000 live births), stratified by race, among three geographic comparison groups of counties. These included: (1) the Northeast Group, near the state border at Memphis, Tennessee; (2) the Central Group, surrounding Little Rock, Arkansas; and (3) the Southwest Group, near Texarkana, Texas. These counties have similar socioeconomic measures and proximity to health care facilities, but are differentiated by limitations imposed by ARHMS' surveillance borders. Maternal age-standardized rates from the control groups were used to impute expected rates, for the Northeast Group and statewide, which were compared with reported rates.
  
  
  RESULTS
  We found that there were 620 fewer reported birth defect cases than expected for the Northeast Group. The Northeast Group's prevalence rates were approximately half of the control groups' rates (310.6 vs. 529.8, respectively, for Whites, and 240.8 vs. 550.1, respectively, for African-Americans). Incorporating the missed cases into statewide prevalence calculations could increase prevalence rates from 502.6 to 523.2 for Whites and from 527.4 to 590.7 for African-Americans.
  
  
  CONCLUSIONS
  This study identified significant regional differences in reported birth defect rates in Arkansas. Case ascertainment might be incomplete in other surveillance systems lacking the means to share data with neighboring systems. Regional inaccuracy can hinder evaluation of localized birth defect trends or targeted prevention efforts.
authors.affiliation: Arkansas Center for Birth Defects Research and Prevention, University of Arkansas for Medical Sciences, Arkansas Children's Hospital Research Institute, 11219 Financial Center Parkway, Suite 250, Little Rock, AR 72211, USA. MosleyBridgetS@uams.edu
authors.forename: Bridget S
authors.initials: BS
authors.lastname: Mosley
authors.forename: Caroline J
authors.initials: CJ
authors.lastname: Simmons
authors.forename: Mario A
authors.initials: MA
authors.lastname: Cleves
authors.forename: Charlotte A
authors.initials: CA
authors.lastname: Hobbs
mesh_terms: D001741:Black or African American / Q000706:statistics & numerical data; D001131:Arkansas / Q000453:epidemiology; D015982:Bias; D000013:Congenital Abnormalities / Q000453:epidemiology*; D006801:Humans; D011159:Population Surveillance; D015995:Prevalence; D013714:Tennessee / Q000453:epidemiology; D014505:Urban Population; D044465:White People / Q000706:statistics & numerical data