Ethical approval
This study was approved by the Institutional Review Board of Kyungpook National University Hospital (IRB No. KNUH 2020-04-049) and performed in accordance with the principles of the Declaration of Helsinki. All personal information was anonymized. Disclosure and sharing of anonymized health insurance data were guaranteed by Korean law, and there was no reason to presume that participants refuse to consent. Because all data was anonymized, the risk of the study due to the waiver of consent was extremely low. Therefore, informed consents for participants waiver were obtained from Institutional Review Board of Kyungpook National University Hospital and Deliberation Committee of National Health Insurance Sharing Service in Korea.
Data source
This cohort study was based on the Korean National Health Insurance (NHI) database. All Korean citizens, more than 50,000,000 people, are obliged to subscribe to the NHI system operated by the Korean government. This health insurance subscription is automatically made at the time of birth. Currently, 97% of Korean citizens are enrolled in this insurance system. The NHI database provides various medical inpatient and outpatient service usage. Information based on the International Classification of Diseases 10th revision (ICD-10) codes, diagnostic codes with treatments, all data on inpatient and outpatient claims, and sociodemographic data of all insured citizens were included in this database.11 The National Health Insurance Service-Infants and Children’s Health Screening (NHIS-INCHS) started in 2007 in South Korea for all children under 6 years of age.12
National Health Insurance Service-Infants and Children’s Health Screening
All infants and children born in Korea in 2019 were eligible to participate in a total of seven children’s health screenings before entering elementary school (at 4–6, 9–12, 18–24, 30–36, 42–48, 54–60, 66–71 months of age). All infants and children born in Korea after 2020 underwent a total of eight screenings (a screening at 14–35 days of age was added). These screenings included the following: questionnaire filled out by the parents, examination by the pediatrician, physical measurement (height, weight, head circumference, BMI), health education, developmental screening, and counseling.13 Moreover, since 2007, all infants and children born in Korea have undergone three oral and teeth examinations by a dentist (at 18–29, 42–53, 54–65 months of age). The dental screening included the current condition of each individual tooth (eruption, noneruption, erupting, demineralization, caries, restoration, pit and fissure sealing, suspicious caries), need for treatment, prevention, plaques, malocclusion, parafunction, caries, proximal caries, restoration, risk for caries, and total judgment of the teeth performed by a dentist. All dental records at 18–29 and 42–53 months were records of primary teeth (milk teeth), and dental records of 54–65 months included records of permanent teeth.
Study population and subgroup analysis
The 5,234,695 newborns born in 2007–2018 in Korea were classified into CL/P and control groups. The diagnosis of CL/P was identified based on ICD-10 codes (Q35–37). CL/P children were further divided into syndromic and nonsyndromic CL/P children based on the presence of associated syndromes. They were also divided into subgroups of cleft lip only (CLO), cleft palate only (CPO), and both cleft lip and palate (CLP) (Fig. 1).
Definition of associated syndromes
Congenital malformation syndromes that predominantly affect facial appearance (Q87.0), such as acrocephalopolysyndactyly, acrocephalosyndactyly (Apert), cryptophthalmos syndrome, cyclopia, Goldenhar syndrome, Gorlin–Chaudhry–Moss syndrome, Moebius syndrome, oro-facial-digital syndrome, Pierre–Robin syndrome, and whistling face, were all included. Velocardiofacial syndrome, which is caused by chromosome 22q11.2 deletion, results in pharyngeal dysfunction, cardiac anomalies, and facial dysmorphia.14 In the CL/P cohort, children identified with codes for congenital cardiac anomalies were categorized as children diagnosed with velocardiofacial syndrome. Since they can also be diagnosed with DiGeorge syndrome, the code for DiGeorge syndrome (D82.1) was also used to identify velocardiofacial syndrome. Mandibulofacial dysostosis (Q75.4) included Franceschetti syndrome and Treacher Collins syndrome. Nager syndrome is characterized by craniofacial and upper limb abnormalities. Acrofacial dysostosis manifests as craniofacial abnormalities in Nager syndrome and exhibits upper limb abnormalities.15 Cases with a combination of craniofacial dysostosis (Q75.1) or mandibulofacial dysostosis (Q75.4) with upper limb abnormalities (Q69 or Q70 or Q71) were identified as having Nager syndrome. Other specified congenital malformation syndromes (Q87.8) included Alport syndrome, Laurence–Moon(–Bardet)–Biedl syndrome, Zellweger syndrome, and CHARGE associations. VACTERL association is typically defined by the presence of three of the following congenital malformations: vertebral defects, anal atresia, cardiac defects, tracheoesophageal fistula, renal anomalies, and limb abnormalities.16 Vertebral defects (Q67.5, Q76.0, Q76.1–Q76.4), anal atresia (Q42.2, Q42.3), cardiac defects (Q20–Q26), tracheoesophageal fistula (Q39.1, Q39.2), renal anomalies (Q60–Q64), and limb abnormalities (Q65–Q74) were identified by ICD-10 codes. When three or more than three malformations were identified among them, VACTERL associations were defined. Congenital malformation syndromes predominantly associated with short stature (Q87.1) included Aarskog, Cockayne, De Lange, Dubowitz, Noonan Prader–Willi, Robinow–Silverman–Smith, Russel–Silver, Seckel, and Smith–Lemli–Opitz syndromes. Finally, congenital malformations, deformations, and chromosomal abnormalities (Q00–Q99) included Down, Edwards, and Patau syndromes, trisomies, monosomies, and chromosomal rearrangement, Turner’s syndrome, sex chromosome abnormalities, and other chromosomal abnormalities (Supplementary Table 1). When CL/P infants had one of above syndromes, they were defined as having syndromic CL/P.
Validation for diagnostic accuracy
For diagnostic accuracy, a total of 437 children who had congenital facial anomalies and visited a single medical center from January 2006 to December 2018 were analyzed by reviewing the medical records. Two plastic surgeons reviewed all medical records, including medical photographs and 3-dimensional facial computed tomography (CT) findings. Cleft lips were identified by medical photographs and cheiloplasty (cleft lip repair). Cleft palates were diagnosed by medical photographs of the palate, 3-dimensional facial CT, and palatoplasty (cleft palate repair). To validate the subgroups of CL/P, CLO patients were defined as only those that were tagged for Q36 and not Q35. Cleft palate only (CPO) was tagged only with code Q35 and not Q36. Patients tagged with both Q35 and Q36 or Q37 were identified as cleft lip and palate (CLP). These algorithms were also used during the review of medical records in a single medical center.
Among all 437 children, 221 diagnosed with CL/P were analyzed for sensitivity, whereas 216 with facial congenital anomalies other than CL/P were analyzed for specificity. The sensitivity of these diagnostic algorithms was assessed by checking whether CL/P infants had satisfied the diagnostic criteria, and the specificity of these algorithms was assessed by determining why infants with congenital facial anomalies other than CL/P did not satisfy the diagnostic criteria. The results revealed that CL/P infants had 99.10% sensitivity and 99.07% specificity. The diagnostic algorithm for subgroup analysis showed 95.65% sensitivity and 97.83% specificity for CLO, 97.39% sensitivity and 99.13% specificity for CPO, and 96.67% sensitivity and 98.33% specificity for CLP.
Statistical analysis
This study compared the general growth (i.e., height, weight, and head circumference) of CL/P and no CL/P children as well as compared their teeth by individual tooth number. These comparisons were performed according to sex, subgroups, and presence of associated syndromes. For general growth, all seven screenings were included in the analysis. Height, weight, and head circumference were divided into 1000 percentiles for the entire cohort. To exclude technical or input errors for each numerical value, numerical values less than the 1st percentile and more than the 999th percentile were excluded. Mean values and standard deviation of the general growth data were calculated for CL/P and no CL/P children according to subgroups and the presence of associated syndromes. Analysis of variance with post hoc test (Scheffe) was used for statistical comparison. Regarding dental and oral examination, the differences regarding eruption, noneruption, erupting, demineralization, caries, restoration, pit and fissure sealing, and suspicious caries were compared. The categorical variables were analyzed using Chi-squared test. Categorical dependent variables, which included the needed treatment, prevention, plaque, malocclusion, parafunction, caries, proximal caries, restoration, risk for caries, and total judgment of the teeth, were also assessed. Logistic regression tests were performed for these categorical dependent variables. All statistical analyses were conducted using STATA MP, version 16.1 (StataCorp, College Station, Texas, USA). Statistical significance was set at p < 0.05.