Download Epidemiology of Cleft Palate in Europe

Epidemiology of Cleft Palate in Europe: Implications for Genetic Research
ELISA CALZOLARI, M.D.
FABRIZIO BIANCHI, B.SC., PH.D.
MICHELE RUBINI, PH.D.
ANNUKKA RITVANEN, M.D.
AMANDA J. NEVILLE, B.SC.
EUROCAT WORKING GROUP
Objective: To describe the epidemiology of cleft palate (CP) in Europe.
Design and Setting: A descriptive epidemiological study on 3852 cases of
CP, identified (1980 through 1996) from more than 6 million births from the
EUROCAT network of 30 registers in 16 European countries.
Results: Significant differences in prevalence in Europe between registries
and within countries were observed. A total of 2112 (54.8%) CP cases occurred
as isolated, 694 (18.0%) were associated with other defects such as multiple
congenital anomalies, and 1046 (27.2%) were in recognized conditions. The
study confirmed the tendency toward female prevalence (sex ratio [SR] 5 0.83),
particularly among isolated cases (SR 5 0.78) even if SR inversion is reported
in some registries. A specific association with neural tube defects (NTDs) in
some registers is reported.
Conclusion: The differences identified in Europe (prevalence, sex, associated anomalies) can be only partially explained by methodological reasons
because a common methodology was shared among all registries for case
ascertainment and collection, and CP is an easy detectable condition with few
induced abortions. The complex model of inheritance and the frequently conflicting results in different populations on the role of genes that constitute risk
factors suggest the presence of real biological differences. The association of
CP/NTD in an area with a high prevalence of NTDs can identify a group of
conditions that can be considered etiologically homogeneous. The epidemiological evaluation can guide genetic research to specify the role of etiological
factors in each different population
KEY WORDS: cleft palate, genetics, epidemiology, etiology, neural tube defects
Cleft palate (CP) is a common congenital anomaly affecting
about 1 in 2000 births, with significant variation depending on
geographical location, racial and ethnic background, and socioeconomic status (Schuttle and Murray, 1999). The frequent
occurrence, as well as psychological, surgical, and dental involvement, emphasize the importance of understanding the
causes.
Most CP cases occur as an isolated congenital malformation,
but CPs are often part of chromosomal and monogenic syndromes or associated with other congenital malformation (multiple congenital anomalies, [MCA]; Shaw et al., 1995; Shuttle
and Murray, 1999; Prescott et al., 2001, Wilkie and MorrissKay, 2001; Beaty et al., 2002). Nonetheless, CP also occurs
as part of many single gene syndromes, and some of these
same genes may also play roles in nonsyndromic orofacial
clefts (Sozen et al., 2001).
The role of genetic factors in determining CP is documented
by recurrence risk (Fraser, 1970) and monozygotic twin concordance (Nordstrom et al., 1996), but thus far there is no
evidence of any single gene acting as a major factor in the
etiology of this orofacial malformation. In isolated CP, a major
genetic component with a relatively small number of interacting causative loci has been suggested, and the final phenotype
is the result of gene products that interact in many ways with
Dr. Calzolari is Professor of Genetic Medicine, Ms. Neville is a Scientific
Secretary, and Dr. Rubini is a Senior Researcher, Genetic Medicine Section,
Department of Experimental Medicine and Diagnostics, University of Ferrara,
Ferrara, Italy. Dr. Bianchi is a Senior Researcher, Unit of Epidemiology, Istituto
di Fisiologia Clinica, Consiglio Nazionale delle Ricerche, Pisa, Italy. Dr. Ritvanen is a Senior Researcher, The Finnish Register of Congenital Malformations, The National Research and Development Centre for Welfare and Health,
Helsinki, Finland. The EUROCAT Working group: Helen Dolk, Professor of
Epidemiology, EUROCAT Central Registry Leader, University of Ulster, Co
Antrim, Northern Ireland, United Kingdom.
Data from this paper were presented orally at the World Health Organization
Meeting on Craniofacial Anomalies, Bauru, Brazil, December 4–6 2001.
Submitted June 2002; Accepted March 2003.
Address correspondence to: Professor E. Calzolari, Professor of Genetic
Medicine, Genetic Medicine Section, Department of Experimental Medicine
and Diagnostics, University of Ferrara, Via L. Borsari 46, 44110 Ferrara, Italy.
E-mail [email protected].
244
Calzolari et al., EPIDEMIOLOGY OF CLEFT PALATE IN EUROPE
one another and the environment (multifactorial-complex disease).
The objectives of this study were to establish the epidemiology of CP in Europe and determine differences in CP prevalence that may be attributed to etiological factors (genetics,
environmental, or both) having a heterogeneous distribution
across European countries.
PATIENTS
AND
METHODS
Data Collection
Data from 30 centers in the 16 European countries of the
European Concerted Action on Congenital Anomalies and
Twins (EUROCAT) network of regional registers of congenital
anomalies in Europe were considered for the study period 1980
through 1996 (Table 1). Recorded cases included live births,
stillbirths, and induced abortions following prenatal diagnosis.
Cases of CP born in the study period from mothers resident
in the study area were considered and classified as the following: (1) isolated CP in which no other anomaly or anomalies
are present, but the presence of minor anomalies such as low
set ears or clinodactyly did not change the eligibility of the
case to be considered isolated; and (2) associated CP in which
two or more unrelated anomalies were present. This group was
further classified into CP in recognized conditions, which comprise CP in chromosomal, monogenic, and environmental syndromes, or part of malformative sequences; or CP in MCA of
unknown etiology, including all cases in which at least one
major anomaly occurred in addition to CP.
All cases were classified according to the EUROCAT definitions (EUROCAT, 1997) and coded according to the British
Pediatric Association Classification of diseases (1977). Multiple sources of ascertainment were used, including birth certificates, pediatric records, maternity records, hospital discharge
summaries, and cytology and pathology reports. Reliance on
different sources varied according to which information sources were available in each area. Completeness of data was ensured by verifying medical records.
Data Validation
Validation of the database was carried out by a medical geneticist (EC) checking each individual record. The EUROCAT
Registry leaders were involved in the data validation process,
in both specification and classification of some complex cases
and the interpretation and general discussion of the results.
Registers and methods have also been described by Dolk et
al. (1991) and in a EUROCAT (2002) report.
Statistical Methods
Prevalence rate was defined as the number of affected cases
in live births, stillbirths, and induced abortions divided by the
total number of births.
For geographical comparisons, differences among centers
245
were analyzed using the chi-square test for heterogeneity (Armitage, 1955). Prevalence rate ratios (PRRs) were calculated
to compare prevalence rates observed in a group of registers,
compared with other groups of registers. The 95% confidence
intervals (CIs) were calculated using the Cornfield (1956)
method. Sex ratios (SRs) were calculated by dividing the male
prevalence by the female prevalence.
RESULTS
Of the 3852 cases of CP derived from 6,181,499 births
(prevalence 6.2 3 10,000; 95% CI 5 6.0 to 6.4), 2112 (54.8%)
cases were isolated, 694 (18.0%) were associated with other
defects such as MCAs, and 1046 (27.2%) were in recognized
conditions (Table 1). There was a significant difference in
prevalence rate of CP among European centers not only for
total cases (chi-square 5 254.5; df 5 29; p , .001) but also
for isolated CP (chi-square 5 220.9; df 5 29; p , .001), MCA
(chi-square 5 81.7; df 5 29; p , .001), and recognized conditions (chi-square 5 234.2; df 5 29; p , .001). Relevant
differences between registries were observed even within the
same country (Table 1), and a significant north-south decreasing trend was not visible.
High CP frequency was observed in Finland (PRR 5 2.60;
95% CI 5 2.34 to 2.89) when compared with other registers,
essentially due to an excess of isolated CP (PRR 5 2.95; 95%
CI 5 2.58 to 3.38) and recognized conditions (PRR 5 2.97;
95% CI 5 2.45 to 3.60) but not MCA (PRR 5 1.09; 95% CI
5 0.76 to 1.57).
The study confirmed a female excess (SR 5 0.83) with a
higher female excess among isolated CP (SR 5 0.78) than
MCA cases (SR 5 0.87) and recognized conditions (SR 5
0.91). A male excess and SR inversion were reported in some
registers.
As reported in the literature, CP cases occur frequently associated with other defects (1740 of 3852 cases; 45.2%). Three
registers in the United Kingdom (Belfast, Glasgow, and Liverpool) and the registers of Odense (Denmark) and Northern
Netherlands accounted for 38.8% of MCA cases and showed
a prevalence ratio of 1.7 per 10,000, compared with 1.0 in the
other EUROCAT registers (PRR 1.8; 95% CI 5 1.5 to 2.1;
Table 2). In these five registers, a relatively high rate of NTDassociated CP cases was observed, with a prevalence rate of
0. 31/10,000, compared with the 0.09/10,000 of the other EUROCAT registers (PRR 5 3.5; 95% CI 5 2.3 to 5.7; Table 2).
These registers have an NTD prevalence rate of 21.2 3
10,000, compared with 9.2/10,000 of the other EUROCAT
registers (PRR 5 2.3; 95% CI 5 2.2 to 2.4; EUROCAT, 1995,
1997, 2002). The registry of Dublin, with a prevalence rate of
CP in MCA of 0.8/10,000 (Table 1) and an NTD prevalence
rate of 24.0/10,000, presents the specific association NTD/CP
(5 of 30 cases).
In the same group of registers in the CP/NTD cases, females
were more frequent (SR 5 0.43; 95% CI 5 0.19 to 0.68),
compared with the other EUROCAT registers for the same CP/
95% CI
1.1–4.2
1.4–2.3
1.2–2.0
2.7–4.3
0.9–2.0
0.3–1.5
3.8–5.5
1.6–2.8
0.6–1.7
0.0–1.8
1.1–2.3
0.1–0.9
1.3–2.0
1.5–2.5
1.7–3.1
0.0–0.4
1.8–2.6
0.7–1.7
0.0–0.8
1.0–1.6
1.2–2.0
0.4–1.0
0.0–0.8
0.5–1.4
0.5–2.9
0.8–3.3
0.2–1.7
1.4–3.1
0.0–1.0
0.4–2.3
1.6–1.8
Rate
2.6
1.8
1.6
3.5
1.5
0.9
4.6
2.2
1.2
0.7
1.7
0.5
1.6
2.0
2.4
0.2
2.2
1.2
0.4
1.3
1.6
0.7
0.4
1.0
1.7
2.0
1.0
2.2
0.4
1.4
1.7
No.
11
65
66
75
27
8
118
50
18
2
30
7
96
56
48
5
97
19
3
93
58
16
3
17
8
10
6
25
1
8
1,046
95% CI
0.0–0.0
0.5–1.1
1.1–1.9
1.3–2.5
1.2–2.5
1.0–2.8
0.8–1.7
1.2–2.3
0.3–1.2
0.0–1.1
0.9–2.0
0.0–0.6
0.9–1.5
0.8–1.6
1.1–2.2
0.7–1.6
0.6–1.1
0.7–1.7
0.4–1.8
0.6–1.0
0.8–1.5
0.4–1.1
0.2–1.6
0.1–0.7
0.3–2.3
0.2–2.2
0.0–1.0
0.2–1.2
0.0–1.7
0.7–2.8
1.0–1.2
Rate
0.0
0.8
1.5
1.9
1.8
1.9
1.2
1.8
0.8
0.4
1.4
0.3
1.2
1.2
1.6
1.2
0.9
1.2
1.1
0.8
1.2
0.8
0.9
0.4
1.3
1.2
0.5
0.7
0.7
1.7
1.1
No.
0
30
62
40
34
17
31
41
12
1
25
4
70
33
32
27
38
19
9
58
44
18
7
7
6
6
3
8
2
10
694
95% CI
0.8–3.6
4.0–5.4
2.0–3.0
2.7–4.3
2.7–4.4
3.2–6.0
8.1–10.5
2.2–3.5
2.7–4.6
0.7–4.6
2.4–4.0
1.9–3.6
1.9–2.6
3.4–5.0
3.8–5.7
1.9–3.2
2.8–3.8
2.5–4.4
2.6–5.2
2.5–3.2
2.7–3.8
2.5–3.9
1.3–3.5
1.8–3.3
1.1–4.0
1.2–4.0
0.9–3.2
1.4–3.1
0.0–2.8
2.8–6.2
3.3–3.6
Rate
2.2
4.7
2.5
3.5
3.5
4.6
9.3
2.8
3.6
2.6
3.2
2.7
2.3
4.2
4.8
2.6
3.3
3.5
3.9
2.8
3.2
3.2
2.4
2.6
2.6
2.6
2.1
2.2
1.4
4.5
3.4
No.
9
169
100
75
65
41
237
65
56
7
57
38
132
117
95
60
146
55
33
204
120
74
19
45
12
13
13
25
4
26
2,112
95% CI
2.7–6.9
6.5–8.3
4.9–6.4
7.7–10.2
5.6–8.0
5.6–9.2
13.7–16.7
5.8–7.9
4.4–6.7
1.4–6.1
5.1–7.5
2.5–4.5
4.5–5.7
6.4–8.4
7.5–10.1
3.1–4.7
5.6–7.1
4.7–7.0
3.8–6.9
4.4–5.5
5.2–6.8
3.8–5.6
2.4–5.1
3.0–4.9
3.4–7.7
3.7–8.0
2.0–4.9
3.9–6.5
0.6–4.3
5.4–9.9
6.0–6.4
Rate
4.8
7.4
5.6
8.9
6.8
7.4
15.2
6.8
5.5
3.7
6.3
3.5
5.1
7.4
8.8
3.9
6.4
5.9
5.3
5.0
6.0
4.7
3.7
4.0
5.6
5.8
3.5
5.2
2.5
7.6
6.2
20
264
228
190
126
66
386
156
86
10
112
49
298
206
175
92
281
93
45
355
222
108
29
69
26
29
22
58
7
44
3,852
Recognized Conditions
No.
MCA
41,549
357,457
405,352
212,677
184,530
89,349
253,847
228,599
155,215
26,680
177,885
140,061
585,049
276,574
199,055
233,877
442,197
158,754
84,715
716,939
371,499
230,455
77,957
174,082
46,558
49,587
63,054
111,750
28,506
57,640
6,181,449
* EUROCAT 5 European Concerted Action on Congenital Anomalies and Twins.
Period
1981–1994
1980–1996
1980–1994
1980–1996
1980–1988
1980–1996
1993–1996
1981–1996
1991–1996
1980–1989
1980–1996
1980–1990
1981–1996
1985–1996
1982–1996
1987–1996
1988–1996
1985–1996
1983–1996
1981–1996
1981–1996
1980–1996
1980–1990
1993–1996
1990–1995
1990–1996
1992–1996
1990–1996
1993–1996
1986–1996
Centers
Galway (Ireland)
Dublin (Ireland)
Belfast (UK)
Glasgow (UK)
Liverpool (UK)
Odense (Denmark)
Finland
Northern Netherlands
Southwest Netherlands
Luxemburg
HainautNamur (Belgium)
West Flanders (Belgium)
Paris (France)
Bouches-du-Rhône (France)
Strasbourg (France)
Saxony-Anhalt (Germany)
Switzerland
Styrian (Austria)
Zagreb (Croatia)
Northeast Italy
Emilia-Romagna (Italy)
Tuscany (Italy)
Umbria (Italy)
Campania (Italy)
Southern Portugal
Asturias (Spain)
Barcelona (Spain)
Basque Country (Spain)
El Valles (Spain)
Malta
EUROCAT mean rate
Isolated
Total
Births
All Cleft Palate
TABLE 1 EUROCAT Registers: Prevalence Rates of Cleft Palate (Live Births, Stillbirths, and Interrupted Pregnancies) per 10,000 Births
246
Cleft Palate–Craniofacial Journal, May 2004, Vol. 41 No. 3
0.12–0.14
0.13
80
11.1–11.6
11.3
694
6,181,449
1.1
1.0–1.2
7011
8.9–9.4
9.2
4635
0.9–1.1
500
5,060,942
* Includes the registers of Odense, Denmark; Northern Netherlands; and Liverpool, Glasgow, and Belfast, United Kingdom. Rates are per 10,000 births. NTD data are from EUROCAT (1995, 1997, 2002). CP 5 cleft palate; MCA 5 multiple congenital
anomalies; NTD 5 neural tube defects; EUROCAT 5 European Concerted Action on Congenital Anomalies and Twins; CI 5 confidence interval; PRR 5 prevalence rate ratio.
45
0.09
0.08–0.10
2.3–5.7
3.5
0.28–0.35
0.31
35
2.2–2.4
2.3
1.0
NTD
20.4–22.1
21.2
2376
1.5–2.1
1.8
1.5–2.0
1.7
194
1,120,507
Odense, Northern Netherland, Glasgow, Liverpool, Belfast
Other EUROCAT Registers
Total
CP/NTD
PRR
95% CI
PRR
No.
CP in MCA
95% CI
Rate
No.
Total Births
Groups of Registers
TABLE 2 Prevalence of CP in MCA, NTD, and NTD-Associated CP in European Area*
Rate
95% CI
PRR
95% CI
No.
Rate
95% CI
95% CI
Calzolari et al., EPIDEMIOLOGY OF CLEFT PALATE IN EUROPE
247
NTD association (SR 5 1.06, 95% CI 5 0.72 to 1.38; Fisher
p 5 0.10).
In Finland, the register with the highest CP prevalence rate,
the CP/NTD association had a low prevalence rate of 0.12/
10,000, which is similar to the other EUROCAT register rate
of 0.13/10,000 (Table 2).
DISCUSSION
Efforts have been made to record the global frequency of
CP, and many different figures are available. In the present
study, covering more than 6 million births, prevalence of CP
varied significantly in Europe, not only between registries but
also within countries, with a European mean value of 6.2 3
10,000. The highest prevalence of isolated CP was confirmed
in Finland during a longer study (ICBDMS, 2000).
Our study showed a tendency toward female prevalence
(Schuttle and Murray, 1999,) although a male excess was reported in some registers. No generally accepted explanation
for these sex differences is reported. The recent discovery of
the X-linked CP and ankyloglossia gene TBX22 (Braybrook
et al., 2001) may suggest a candidate gene that might be relevant for palate morphogenesis and possibly play a role in the
imbalanced sex prevalence of nonsyndromic CP cases.
An association of CP and NTD in registers of Belfast, Liverpool, Glasgow, Dublin, northern Netherlands, and Odense
was found with epidemiologic characteristics (spatial and sex
distribution) similar to those of isolated NTD. Our data suggest
that common factors may be involved in the etiology of NTD
and other anomalies, this factor varying geographically (Calzolari et al., 1997). Dolk et al. (1991) reported that the association between NTD and a number of anomaly groups was
at least two times more prevalent in the United Kingdom and
Ireland than in continental Europe and Malta. Three possible
non–mutually exclusive explanations of these data might be
offered.
Ascertainment Procedure
This factor could contribute, but in a quite marginal manner
because common methodology was shared among all registries
for case ascertainment and collection; multiple sources of information were used by most registries; and CP is an easily
diagnosed and reported malformation with a reduced impact
from cases of induced abortion. Birth cut-off dates are not a
critical factor, producing only small differences between registries with different cut-off dates for registration following
diagnosis.
Genetics
The growth of the detailed structures of the head and face
is largely determined genetically (Wilkie and Morriss-Kay,
2001), and these processes are known to be dependent on a
spectrum of signaling molecules, transcription factors, and
growth factors interacting with environmental factors.
248
Cleft Palate–Craniofacial Journal, May 2004, Vol. 41 No. 3
Many genes have been indicated to play a role in CP etiology (Murray, 1995; Schuttle and Murray, 1999; Beatty et al.,
2002), each one possibly contributing to the genetic susceptibility in a complex network of gene-gene and gene-environment interactions. CP also occurs as part of many single gene
syndromes, and some of these same genes may also play roles
in nonsyndromic CP (Sozen et al., 2001).
Association studies have looked at various CP candidate
genes, chosen for their known biology or by positional localization within genomic regions implied in linkage studies. As
in many other association studies, nonreplication in subsequent, independent studies has been reported (Spritz, 2001;
Murray, 2002). No simple explanation for these conflicting
data is possible. Chance associations, variations in study design, or differences in the frequencies of allelic variants that
truly predispose to CP among different populations can be hypothesized. In the latter case, the same candidate gene or DNA
variants may be associated with different relative risks in different populations, and the nonreplication might result from
real biological differences. Studies on many other multifactorial-complex diseases (Reich and Lander, 2001) have pointed
to the need to know not only the loci at which a mutation
occurs but also the relation between the genes involved and
the allele frequencies within and between populations. Geographical variations in gene frequencies of mutations or polymorphisms that are risk factors for CP could explain the observed differences in the prevalence of this condition.
According to the model for complex diseases by Greenspan
(2001), if several factors contribute to the phenotype (CP has
a complex heterogeneous etiology), the same output can be
produced in different ways (Fig. 1a and 1b) with the clinical
phenotype being highly influenced by the type of mutation, the
effect of other genes, and environmental factors. Complex
pathways through this network of gene-gene and gene-environment interaction may provide alternative routes through
which CP may be developed or avoided. Recently considerable
attention has been paid to the possible role of folic acid in
orofacial clefts. The manner in which folic acid is involved is
less clear than that demonstrated for NTDs. Alteration of the
metabolism of folate could be a shared susceptibility factor
(Fig. 1c) and can contribute to explain the association between
CP and NTDs in an area with high prevalence of NTDs.
Homozygosity for the 677T variant in methylene-tetrahydrofolate reductase in CP patients (Mills et al., 1999) can be
one of the possible link factors between alteration of folic acid
metabolism and the occurrence of oral clefts or NTDs in offspring as a specific association, part of a common network.
Folate could be linked to the etiology of NTDs and other
anomalies such as omphalocele (Calzolari et al., 1997). Alternatively, the presence of a defect may predispose to subsequent
malformation of specific structures or may be an essential
component of sequence or field defects (neural crest).
Environment
Genes involved in the development of the face are influenced by environmental teratogens (e.g., smoke, alcohol; Shaw
FIGURE 1 Proposed gene network interaction in determining cleft palate
(CP). A. Normal interaction between genes prevents CP from developing.
B. Mutations (yellow dots) in genes along a molecular network can lead to
cleft palate. C. Shared mutations can determine CP associated with neural
tube defects (NTDs). Modified from Greenspan (2001).
et al., 1996) and maternal nutrition (Murray, 2002). The precise mechanisms by which these environmental teratogens lead
to clefts are unknown, even if it could be related to the genetic
background linked to functional variation in gene expression.
CONCLUSIONS
Gene/environment research should seek to establish the risk
of CP associated with different populations and ethnic groups
and be able to differentiate exposure and the genetic predisposition. Identification of those at risk could then lead to selective counseling. Integration of new genetic information (biological sample collection and genetic analysis) into epidemiological studies in the same population can help clarify links
between etiological factors and different prevalence in different populations so providing the direction for genetic research.
Acknowledgments. The EUROCAT project is funded under the Rare Diseases
Program of the European Commission. Funding was also received from the
Emilia-Romagna Region and the Tuscany Region and for which we are grateful.
The authors thank all the physicians, nurses, midwives, and Registry clerks for
their assistance in collecting the data. The EUROCAT Registries that participated in the study are: Styria, Austria, Martin Haeusler; West Flanders, Belgium, Vera Nelen; Hainaut, Belgium, Yves Gillerot; Zagreb, Croatia, Ingeborg
Calzolari et al., EPIDEMIOLOGY OF CLEFT PALATE IN EUROPE
Barisic; Odense, Denmark, Ester Garne; Finland, Annukka Ritvanen, Jorma
Rautio; Bouche du Rhone, France, Nicole Philipe, Segolene Ayme; Paris,
France, Catherine De Vigan, Janine Goujard; Strasbourg, France, Claude Stoll;
Saxony-Anhalt, Germany, Volker Steinbicker; Dublin, Ireland, Bob McDonnell,
Zachary Johnson; Galway, Ireland, David Lillis; Campania, Italy, Gioacchino
Scarano; Emilia Romagna, Italy, Elisa Calzolari, Amanda Neville, Gianni Astolfi; North East Italy, Romano Tenconi; Tuscany, Italy, Fabrizio Bianchi, Sonia
Catalano, Anna Pierini; Umbria, Italy, Anna Calabro; Luxembourg, D. HansenKoenig, M. Roulleaux; Malta, Miriam Gatt; South Portugal, Maria Feijoo; Asturias, Spain, Carmen Mosquera-Tenreiro; Barcelona, Spain, Joaquin Salvador;
Basque Country, Spain, Sixto Garcia Minaur; El Valles, Spain, Rosa Caballin;
Switzerland, Marie-Claude Addor; North Netherlands, Hermien De Walle; Belfast, United Kingdom, Norman Nevin; Glasgow, United Kingdom, David
Stone; and Liverpool, United Kingdom, P. J. Howard.
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