title: How valid are the rates of Down syndrome internationally? Findings from the International Clearinghouse for Birth Defects Surveillance and Research.
abstract: Rates of Down syndrome (DS) show considerable international variation, but a systematic assessment of this variation is lacking. The goal of this study was to develop and test a method to assess the validity of DS rates in surveillance programs, as an indicator of quality of ascertainment. The proposed method compares the observed number of cases with DS (livebirths plus elective pregnancy terminations, adjusted for spontaneous fetal losses that would have occurred if the pregnancy had been allowed to continue) in each single year of maternal age, with the expected number of cases based on the best-published data on rates by year of maternal age. To test this method we used data from birth years 2000 to 2005 from 32 surveillance programs of the International Clearinghouse for Birth Defects Surveillance and Research. We computed the adjusted observed versus expected ratio (aOE) of DS birth prevalence among women 25-44 years old. The aOE ratio was close to unity in 13 programs (the 95% confidence interval included 1), above 1 in 2 programs and below 1 in 18 programs (P < 0.05). These findings suggest that DS rates internationally can be evaluated simply and systematically, and underscores how adjusting for spontaneous fetal loss is crucial and feasible. The aOE ratio can help better interpret and compare the reported rates, measure the degree of under- or over-registration, and promote quality improvement in surveillance programs that will ultimately provide better data for research, service planning, and public health programs.
authors.affiliation: Centre of the International Clearinghouse for Birth Defects Surveillance and Research, Roma, Italy.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Leoncini
authors.forename: Lorenzo D
authors.initials: LD
authors.lastname: Botto
authors.forename: Guido
authors.initials: G
authors.lastname: Cocchi
authors.forename: Goran
authors.initials: G
authors.lastname: Annerén
authors.forename: Carol
authors.initials: C
authors.lastname: Bower
authors.forename: Jane
authors.initials: J
authors.lastname: Halliday
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Amar
authors.forename: Marian K
authors.initials: MK
authors.lastname: Bakker
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Bianca
authors.forename: Maria Aurora
authors.initials: MA
authors.lastname: Canessa Tapia
authors.forename: Eduardo E
authors.initials: EE
authors.lastname: Castilla
authors.forename: Melinda
authors.initials: M
authors.lastname: Csáky-Szunyogh
authors.forename: Saeed
authors.initials: S
authors.lastname: Dastgiri
authors.forename: Marcia L
authors.initials: ML
authors.lastname: Feldkamp
authors.forename: Miriam
authors.initials: M
authors.lastname: Gatt
authors.forename: Fumiki
authors.initials: F
authors.lastname: Hirahara
authors.forename: Danielle
authors.initials: D
authors.lastname: Landau
authors.forename: R Brian
authors.initials: RB
authors.lastname: Lowry
authors.forename: Lisa
authors.initials: L
authors.lastname: Marengo
authors.forename: Robert
authors.initials: R
authors.lastname: McDonnell
authors.forename: Triphti M
authors.initials: TM
authors.lastname: Mathew
authors.forename: Margery
authors.initials: M
authors.lastname: Morgan
authors.forename: Osvaldo M
authors.initials: OM
authors.lastname: Mutchinick
authors.forename: Anna
authors.initials: A
authors.lastname: Pierini
authors.forename: Simone
authors.initials: S
authors.lastname: Poetzsch
authors.forename: Annukka
authors.initials: A
authors.lastname: Ritvanen
authors.forename: Gioacchino
authors.initials: G
authors.lastname: Scarano
authors.forename: Csaba
authors.initials: C
authors.lastname: Siffel
authors.forename: Antonin
authors.initials: A
authors.lastname: Sípek
authors.forename: Elena
authors.initials: E
authors.lastname: Szabova
authors.forename: Giovanna
authors.initials: G
authors.lastname: Tagliabue
authors.forename: Stein Emil
authors.initials: SE
authors.lastname: Vollset
authors.forename: Wladimir
authors.initials: W
authors.lastname: Wertelecki
authors.forename: Ludmila
authors.initials: L
authors.lastname: Zhuchenko
authors.forename: Pierpaolo
authors.initials: P
authors.lastname: Mastroiacovo
mesh_terms: D000328:Adult; D004314:Down Syndrome / Q000453:epidemiology*; D005260:Female; D036281:Genetic Research; D006801:Humans; D038622:Internationality; D008423:Maternal Age; D011159:Population Surveillance; D011247:Pregnancy; D015203:Reproducibility of Results