How valid are the rates of Down syndrome internationally? Findings from the International Clearinghouse for Birth Defects Surveillance and Research.
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.
Leoncini
Emanuele
E
Centre of the International Clearinghouse for Birth Defects Surveillance and Research, Roma, Italy.
Botto
Lorenzo D
LD
Cocchi
Guido
G
Annerén
Goran
G
Bower
Carol
C
Halliday
Jane
J
Amar
Emmanuelle
E
Bakker
Marian K
MK
Bianca
Sebastiano
S
Canessa Tapia
Maria Aurora
MA
Castilla
Eduardo E
EE
Csáky-Szunyogh
Melinda
M
Dastgiri
Saeed
S
Feldkamp
Marcia L
ML
Gatt
Miriam
M
Hirahara
Fumiki
F
Landau
Danielle
D
Lowry
R Brian
RB
Marengo
Lisa
L
McDonnell
Robert
R
Mathew
Triphti M
TM
Morgan
Margery
M
Mutchinick
Osvaldo M
OM
Pierini
Anna
A
Poetzsch
Simone
S
Ritvanen
Annukka
A
Scarano
Gioacchino
G
Siffel
Csaba
C
Sípek
Antonin
A
Szabova
Elena
E
Tagliabue
Giovanna
G
Vollset
Stein Emil
SE
Wertelecki
Wladimir
W
Zhuchenko
Ludmila
L
Mastroiacovo
Pierpaolo
P
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