What Is Known
- Digestive and respiratory morbidity is frequent in children with esophageal atresia/tracheoesophageal fistula.
- Follow-up care should be provided to support esophageal atresia/tracheoesophageal patients’ health-related quality-of-life.
- Condition-specific quality-of-life questionnaires for esophageal atresia/tracheoesophageal children aged 2 to 7 years (parent-report) and 8 to 17 years (child-and-parent-report) have recently been developed and pilot-tested in Sweden and Germany.
What Is New
- The final “EA-QOL-questionnaires” are valid and reliable measures for use in esophageal atresia/tracheoesophageal children in Sweden and Germany.
- The “EA-QOL-questionnaires” represent new outcome measures to provide important information following different treatments.
- Using the EA-QOL-questionnaires in clinical practice can improve the understanding of esophageal atresia/tracheoesophageal children's health outcomes.
Esophageal atresia (EA) with or without tracheoesophageal fistula (TEF) is a malformation occurring in 2.4/10,000 births (1). Although survival rates today exceed 90% (2), long-term sequelae including dysphagia and gastroesophageal reflux (GER) remain common. Feeding difficulties encompassing food impaction, prolonged meals, and choking are frequent (3–6). Respiratory disorders with recurrent airway infections, cough, and wheezing (7,8), and concomitant anomalies (2), co-contribute to poor health. The European and North American Society for Pediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN-NASPGHAN) guidelines for EA/TEF children (9), emphasize focus on long-term consequences and provision of continuing medical and psychosocial care to support patients’ health-related quality of life (HRQOL) (9). This concept refers to impact of the disease and treatment on daily physical, psychological and social functioning from the patient's perspective (10). In EA/TEF patients, understanding of HRQOL is limited by the use of different generic assessments (11,12). Between 50% and 75% of patients are reported impaired HRQOL (13,14). In 5 generic HRQOL studies, EA/TEF children have either diminished overall HRQOL (15), general health (16), social HRQOL (17) or unaffected overall HRQOL (18,19) compared to healthy norms. In few studies, GER (15,16), and dysphagia (15) negatively impact pediatric HRQOL. Compared to generic questionnaires (20), condition-specific instruments are more sensitive to clinical characteristics and patient-oriented importance (10), and can better identify patients risking a larger disease burden (21). A standardized EA-specific HRQOL questionnaire can potentially augment treatment evaluations (22,23) and information to health care services, schools and patient support groups (24). We developed condition-specific HRQOL instruments for EA/TEF children 2 to 7 and 8 to 17 years old (25), with good psychometric performance in the pilot-test (26). This study objective was to report the final validity and reliability of “the EA-QOL-questionnaires” when used in Sweden and Germany, which we hypothesized to be continuously satisfactory.
Participants and Settings
The study was approved by the Ethical Review Boards of Gothenburg, Sweden (DNR 958–13) and Hannover, Germany (2936–2015). In 2016, families of children 2 to 17 years old with EA Gross type A-E (n = 188) were recruited from the Queen Silvia Children's Hospital in Gothenburg, Sweden (n = 86), the Centre of Pediatric Surgery, Hannover Medical School and Bult Children's Hospital, Hannover, Germany (n = 102). Participants needed to understand Swedish or German. Informed consent was obtained from 182 families.
Medical records were reviewed for birth characteristics, associated anomalies, Gross EA-subtype, and surgical interventions. Sociodemographic information and data on the child's health the previous 4 weeks were collected through a parent-reported, standardized questionnaire. This included questions on digestive and respiratory symptoms, and feeding difficulties.
Health-related Quality of Life Measures
Families, with no participation in the earlier project (25,26), received questionnaires with pre-stamped envelopes for replies, and with intention to increase response rates they received a maximum of 3 reminders. Additional to parent-reports, children ≥8 years old gave self-reports, except for children with cognitive impairments who were represented by parent-report. In order to examine the EA-QOL-questionnaires’ stability over time, test-retest reliability, it was re-sent to respondents with requirements of responses ≤21 days.
The EA-QOL-Questionnaire Field Test Versions
The development, translation and evaluation of the EA-QOL-questionnaires comply with international standards for patient-reported outcome measures (PROMs), as described by the International Society of Pharmacoeconomics and Outcome Research (27–29) and the US Food and Drug Administration (20). Patient and parent input, age-specific considerations, and cross-cultural perspectives were particularly important. Questionnaire development included a literature review of HRQOL in EA/TEF patients (11), standardized focus groups generating HRQOL items (25), item reduction (26), translation, cultural adaption, and pilot-testing in Sweden and Germany (26), which demonstrated sound validity and reliability (25,26). The EA-QOL-questionnaire field test versions consisted of a parent-reported 18-item questionnaire for children between 2 and 7 years old (domains; eating, physical health and treatment, social isolation and stress), and a child-and parent-reported 26-item questionnaire for children aged 8 to 17 years (domains; eating, social relationships, body perception and health, and wellbeing). Questions were answered using a 4-weeks recall period, and a 5-point Likert scale (30).
Generic Health-related Quality of Life Questionnaires
Previously validated generic HRQOL questionnaires were used for psychometric evaluation of the EA-QOL-questionnaires; PedsQL 4.0 age-specific versions were used for children aged 2 to 4, 5 to 7, 8 to 18 years old (31), and DISABKIDS-12 for children 8 to 17 years (32).
Data were analyzed using IBM SPSS Statistics for Windows, (version 22.0, Armonk, NY, USA: IBM Corp) and SAS 9.4 (SAS Institute Inc., Cary, NC, USA). Significant level was P < 0.05. Study population characteristics were presented using median, min/max and percentages. Using Fisher's exact test and Mann-Whitney U test, differences between Swedish versus German respondents, and respondents versus non-respondents were analyzed as to gender, prematurity (gestational age <37 weeks), low birth-weight (<2500 g), Gross A, primary esophageal repair, associated anomalies, and VACTERL.
Responses to the EA-QOL-questionnaires were coded 1–5, where higher points represented better HRQOL. Following psychometric evaluation standards (33,34), and similar to the pilot test (26), items were first evaluated against predefined psychometric criteria, to support their inclusion or exclusion in the final EA-QOL-questionnaires. A detailed description of this procedure is provided in Supplemental Digital Content 1 (https://links.lww.com/MPG/B380). Feasibility was determined from the percentage of missing items. Low values indicated capability of the respondent to provide good quality data regarding HRQOL. The items in the final EA-QOL-questionnaires were linearly transformed to a 0 to 100 scale. Domain and total scores (scales) required ≥70% item responses. Cross-cultural scale descriptors used mean, SD, and the percentage of respondents achieving the maximum possible score (ceiling effect) and minimum possible score (floor effect). Ceiling effects ≤15% reflected a desirable variability of a scale (35).
Internal reliability was concluded if Cronbach's alpha coefficient exceeded 0.7 for the scales. The evaluation of test-retest reliability (stability of scores within 21 days), and child-and parent-scores (comparison reliability) included calculation of the level of agreement between these 2 occasions/raters, using intra-class correlation coefficient (ICC). Moderate (0.5–0.75), Good (0.75–0.9) and excellent (>0.90) levels of ICC were expected (36). Limits of the agreements were also estimated.
Known-groups validity was evaluated by examining subgroups expected to differ in EA-QOL-Total-scores using Mann-Whitney U test, with requirements of at least 5 patients in each subgroup (37). Effect sizes (ESs) were used to estimate the clinical meaningfulness of such differences, using Cohen's d for a standardized interpretation. Moderate (>0.5) and large (>0.8) ESs were regarded as strengthening clinical validity (38). Hypotheses were predefined according to age-specific content of the EA-QOL-questionnaires (Supplemental digital content 1, https://links.lww.com/MPG/B380), as originally generated form child and parent reports (25,26). In both age-related versions, the EA-QOL -Total scores were expected to be lower in either children with no primary esophageal repair, with prior gastrostomy insertion or in children treated with esophageal dilatation. Children with digestive symptoms and feeding difficulties were hypothesized to have lower EA-QOL-Total scores (child- and parent-reports). It was anticipated that respiratory symptoms would be associated with lower EA-QOL-Total-scores in 2 to 7 year olds only. Analyses were performed to establish reference values for both age subgroups.
Clinical concurrent validity was noted if an increased number of different digestive symptoms, feeding difficulties (2–7-year-olds, 8–17-year-olds) or respiratory symptoms (2–7-year-olds) the preceding 4 weeks (simultaneous symptom burden) were related to lower EA-QOL-Total-scores using linear regression analysis.
Convergent validity was examined using Spearman's rho (rs), between the total scores of the EA-QOL-questionnaire and generic HRQOL questionnaires, PedsQL 4.0 and DISABKIDS-12. We expected a moderate (0.40–0.59) to strong (0.60–0.79) correlation (26).
Altogether, 124 families responded to the EA-QOL-questionnaires (overall response rate 68%), including 26/27 Swedish (96%) and 27/55 German (49%) families of children aged 2 to 7 years, and 47/53 Swedish families (89%) and 24/47 German families (51%) of children aged 8 to 17 years. The study population is presented in Table 1. No differences between Swedish and German respondents, or respondents and non-respondents were found (P > 0.05).
Item Evaluation and the Final EA-QOL-Questionnaires
Following item evaluation based on predefined criteria and expert consensus, 1 item (Eating) from the EA-QOL-questionnaire for children 2 to 7 years old was rejected due to item skewness or kurtosis> 2.0, and 2 items from the EA-QOL-questionnaire for children 8 to 17 years old (1 from social relationships and 1 from physical health and well-being), were omitted owing to poor internal reliability in child-and parent-report, as detailed in Supplemental digital content 1 (https://links.lww.com/MPG/B380). The 17-item EA-QOL-questionnaire for children 2 to 7 years (parent-report) consisted of the 3 domains eating (7 items), physical health and treatment (6 items), and social isolation and stress (4 items). Overall feasibility of the questionnaire was good. There were only 3 items (social isolation and stress), which had missing responses >5% (range 5.6%–7.5%). These incomplete responses were from parents of 2 to 3-year-old toddlers. The 24-item EA-QOL-questionnaire for children 8 to 17 years old (child- and parent-report) consisted of the 4 domains eating (8 items), social relationships (7 items), body perception (5 items), and health and well-being (4 items). Twenty-four child-reported items (100%) were completed with missing values <5.0% (range 0%–4.8%) and 21/24 parent-reported items with <6% (range 0%–7.0%). Four incomplete parent-responses (5.6%) represented proxy-reports for their cognitively impaired child, and explained missing item values >5% within all 4 domains (Supplemental digital content 1, https://links.lww.com/MPG/B380).
Descriptives, Internal Consistency and Test-retest Reliability
Descriptives, internal consistency, and retest reliability of the age-specific EA-QOL-questionnaires are shown in Table 2. As desirable, no ceiling effects ≥15% were observed for the EA-QOL-Total scores, however, were noted in 3 scales of the EA-QOL-questionnaires for 2 to 7-year-olds (social isolation and stress) and 8 to 17-year-olds (body perception, health and well-being). In the EA-QOL-questionnaire for children 8 to 17 years old, group comparison reliability showed satisfactory levels of child-parent-agreements on the scales eating (ICC, 0.92), social relationships (ICC, 0.89), body perception (ICC, 0.68), and health and well-being (ICC, 0.96), total scales (ICC, 0.94). Internal consistency reliability was sound in both age-related versions (Cronbach's alpha). In the retest 36% of parents of 2 to 7 years old children responded ≤21 days (days: median 12, range 3–20) and 39% of children (or their parents) 8 to 17 years old (days: median 11, range 5–21). As shown by ICCs, there was a good to excellent agreement in the total and domain scores between field- and retest (child- and parent-reports).
Known-groups validity was supported in both age-related EA-QOL-questionnaires (Table 3). Demonstrating large ESs, the EA-QOL-Total-scores were significantly lower in EA/TEF children 2 to 7 years old with a prior gastrostomy insertion, dysphagia, heartburn, vomiting problems, or any feeding difficulty (P < 0.05). All of the reported respiratory symptoms were significantly associated with lower EA-QOL-Total-scores (moderate-large ESs).
In the EA-QOL-questionnaire for children aged 8–17 years, children who had not had primary esophageal repair (child- and parent-report), or those who had been treated with esophageal dilatation (parent-report), had significantly lower EA-QOL-Total-scores (moderate-large ESs). Moreover, EA/TEF children aged 8 to 17 years with reported dysphagia, heartburn, vomiting problems had significantly lower EA-QOL-Total-scores, as did children who needed to avoid certain foods, eat small portions, drink more fluid during meals or took longer to finish large meals (child- and parent-reports, large ESs). Additionally, dyspnea at physical activity/at rest (child-report) and chest tightness (parent-report) were associated with lower EA-QOL-Total-scores (moderate ESs), P < 0.05.
Clinical Concurrent Validity
Using linear regression, an increased number of different digestive symptoms (dysphagia/heartburn/vomiting-problems) significantly decreased the EA-QOL-total-scores in children 2 to 7 years old (parent-report, n = 46, β0 = 86.5, β1 = -10.7, R2 = 0.55, P < 0.001) and children 8 to 17 years old (child-report: n = 58, β0 = 86.5, β1 = -8.9, R2 = 0.51, P < 0.001; parent-report; n = 61, β0 = 88.9, β1 = -9.0, R2 = 0.48, P < 0.001). An increased number of different feeding difficulties (food restriction/eats small portions/energy-enriched food/adjusted food consistency/>30 minutes to finish a large meal/increased fluid intake to ease swallowing food/food through a gastrostomy/nutritional intake through infusion pump/adult assistance during meals), were also associated with lower EA-QOL-total-scores in 2 to 7-year-olds (parent-report; n = 45, β0 = 82.3, β1 = -4.7, R2 = 0.50, P < 0.001) and children 8 to 17 years old (child-report: n = 58, β0 = 86.8, β1 = -6.2, R2 = 0.45, P < 0.001; parent-report; n = 61, β0 = 89.6, β1 = -7.1, R2 = 0.63 P < 0.001). As expected, a high number among different respiratory symptoms (cough/wheezing/airway infections/dyspnea/chest tightness) significantly decreased the EA-QOL-Total-scores only in 2 to 7-year-olds (parent-report, n = 43, β0 = 82.1, β1 = -5.4, R2 = 0.21, P = 0.002).
Convergent validity was demonstrated in both age-related versions of EA-QOL-questionnaires (child- and parent-report). The EA-QOL-Total-scores for children aged 2 to 7 years showed a moderate correlation (n = 53, rs = 0.66) with those on the PedsQL 4.0. The EA-QOL-Total-scores for children 8 to 17 years old demonstrated a moderate correlation (child-report, n = 58, rs = 0.68; parent-report, n = 59, rs = 0.61) with the Total scores on PedsQL 4.0, and a strong correlation with those on the DISABKIDS-12 in the child-report (n = 57, rs = 0.83), although a weaker correlation according to the parent-report (n = 60 rs = 0.47).
The EA-QOL-questionnaires for children 2 to 7 years (parent-report) and 8 to 17 years (child-and parent-report) are the first reported condition-specific HRQOL instruments for children with EA/TEF. Taken together with the careful developmental process and pilot-test (25,26), this study demonstrated overall satisfactory psychometric properties in Sweden and Germany (Fig. 1). In addition to generic instruments, the need for targeted HRQOL and psychosocial measures has been increasingly recognized in pediatric gastrointestinal disorders (39–42). In 2016, the ESPGHAN-NASPGHAN guidelines for EA/TEF children declared that follow-up care for patients is essential for patients’ HRQOL (9). The EA-QOL-questionnaires aim to capture issues important to EA/TEF children, and to provide clinically relevant information. Implementation of such PROMs in outpatient clinics can strengthen child-clinician communication of HRQOL issues, and add to the understanding and enhancement of a patient's health outcome, along with new areas of interventions (24). The EA-QOL-questionnaires can also standardize long-term evaluations of different pediatric surgical treatments.
As desirable, the EA-QOL-instruments showed substantial discriminative ability (21) with regard to digestive morbidity, reflecting esophageal symptoms and feeding difficulties to have a negative impact on EA-QOL in childhood and adolescence. A possible explanation is that aspects of “Eating” form a conceptual component of condition-specific HRQOL and is measured in each age-related EA-QOL-Total-scores (25,26). Compared to generic HRQOL studies, GER disease has been shown to impair physical HRQOL (15,16), while dysphagia affects emotional HRQOL (15). Studies have recorded feeding difficulties in EA/TEF children (4,5), but not their effect on HRQOL using validated questionnaires. Consistent with airway disorders being more frequent in younger children (14), respiratory symptoms in our previous study (25) showed primary relevance to younger patients’ condition-specific HRQOL. As hypothesized, respiratory problems reduced EA-QOL-total-scores in young children. Although not required for known-groups validity, the EA-QOL-instrument for 8 to 17-year-olds had some discriminative ability regarding severe airway disorders, with dyspnea and chest tightness associated with lower EA-QOL-Total-scores. Co-morbidities in the study sample, such as cardiovascular (38.0%) or respiratory anomalies (8.4%), could help to explain this. Lepeytre et al. showed that pneumonia and hospitalization due to a respiratory event negatively affected HRQOL (18). Although generic HRQOL instruments measure different constructs, together they indicate that severe airway problems may affect older EA/TEF children's HRQOL.
Hypotheses regarding the relationship between surgical variables and future HRQOL are complex. Following neonatal surgery children may develop coping strategies with increased age (43), and morbidity may decrease (44), which will also affect HRQOL. Esophageal dilation may indicate higher levels of disease, but its aim is to relieve patients’ symptoms. However, prior gastrostomy insertion in 2 to 7-year-olds, and “no primary esophageal repair” and esophageal dilatation in 8 to 17-year-olds, were associated with lower EA-QOL-Total scores. Small sample sizes combined with heterogeneity, related to different frequency and severity of concomitant anomalies, may explain why only 8 to 17-year-olds with long-gap EA had significantly worse EA-QOL-total scores. Different questions asked within each of the age-specific instruments may also influence these results. The impact of scarring on HRQOL in 8 to 17-years-olds is an important finding, while in 2 to 7-year-olds the lack of this impact may reflect cohort effects due to an increased use of muscle- and nerve-sparing thoracotomy and thoracoscopic repair during the past decennium. Therefore the results should be carefully interpreted.
The EA-QOL-questionnaires demonstrated acceptable convergent validity (26). Ceiling effects ≥15% were observed in 1 domain on the questionnaire for children aged 2 to 7 years, and 2 domains on the questionnaire for 8 to 17-year-olds (35). In rare diseases, small sample size and heterogeneity are known challenges (28), which can co-contribute to ceiling effects (reports of no problems) in PROMs (35). Considering the broad age span of the EA-QOL-questionnaires and clinical heterogeneity of EA/TEF, ceiling effects could be expected and are observed also in well-established HRQOL instruments (33,40,41,45).
Internal consistency and retest-reliability were satisfactory. Although the retest sample was international it was small and with indications of higher disease severity. The retest time, considered the balance between the results to be contaminated by memory and patients’ health instability. On the first measurement (field-test) families received reminders to respond to the questionnaires. Prior to the investigation, we decided to accept a lower response rate in the retest to avoid burdening participating families.
Generalizability is supported by an international study design, and overall satisfactory Swedish-German feasibility, validity and reliability of the EA-QOL-questionnaires. Reference values of EA-QOL-Total scores in important clinical subgroups, with ESs to demonstrate clinical meaningfulness, are unique to this study. The total response rate was acceptable, but differed between the countries despite standardized data collection. A co-contributing factor may be that the Swedish centralized care to EA/TEF patients, which differs to the German decentralized health care, reinforces the caregiver relationship and families’ willingness to participate in research. However, all study centers provide standardized follow-up care. Moreover, the cross-cultural samples seem representative for EA/TEF children (8,15), and Swedish-German samples statistically clinically comparable between the countries. Similar and lower levels of associated anomalies are reported (2,15,46). A high frequency of associated anomalies in children 8 to 17 years may be explained by the many types of registered anomalies. Associated anomalies may influence the EA-QOL-outcomes, but were not a part of the validation study. The literature provides no uniform definition of dysphagia, heartburn, or vomiting problems, and this study is limited by the use of self-developed clinical questions and definitions. Limitations are also that symptoms were parent-reported, symptom-severity scores and medical examinations were not employed. The age-specific EA-QOL-questionnaires should be used with the knowledge that 3 scales may have less precision of the healthy end scale. Although item relevance, clarity, and adequacy were pilot-tested (26), age-related and clinical heterogeneity (41) in EA/TEF children may explain missing item responses. Feasibility of social/school questions may be lower for parents of toddlers, and parents of children with cognitive impairments may find it difficult to answer several EA-QOL-questions. Future research is needed to evaluate the EA-QOL-questionnaires in other countries, and to investigate the relationships between condition-specific HRQOL in EA/TEF children and physiological characteristics, family impact, and coping mechanisms.
We would like to acknowledge funding received by the Queen Silvia Jubilee Foundation, the Sven Jerring Foundation and ALF Grants from Region of Västra Götaland.
1. Pedersen RN, Calzolari E, Husby S, et al. Oesophageal atresia: prevalence, prenatal diagnosis and associated anomalies in 23 European regions. Arch Dis Child
2. Sfeir R, Piolat C, Lemelle JL, et al. Esophageal atresia: data from a national cohort. J Pediatr Surg
3. Presse N, Taillefer J, Maynard S, et al. Insufficient body weight of adults born with esophageal atresia. J Pediatr Gastroenterol Nutr
4. Gottrand M, Michaud L, Sfeir R, et al. Motility, digestive and nutritional problems in esophageal atresia. Paediatr Respir Rev
5. Menzies J, Hughes J, Leach S, et al. Prevalence of malnutrition and feeding difficulties in children with esophageal atresia. J Pediatr Gastroenterol Nutr
6. Catalano P, Di Pace MR, Caruso AM, et al. Gastroesophageal reflux in young children treated for esophageal atresia: evaluation with pH-multichannel intraluminal impedance. J Pediatr Gastroenterol Nutr
7. Olbers J, Gatzinsky V, Jonsson L, et al. Physiological studies at 7 years of age in children born with esophageal atresia. Eur J Pediatr Surg
8. Malmstrom K, Lohi J, Lindahl H, et al. Longitudinal follow-up of bronchial inflammation, respiratory symptoms, and pulmonary function in adolescents after repair of esophageal atresia with tracheoesophageal fistula. J Pediatr
9. Krishnan U, Mousa H, Dall’Oglio L, et al. ESPGHAN-NASPGHAN Guidelines for the Evaluation and Treatment of Gastrointestinal and Nutritional Complications in Children With Esophageal Atresia-Tracheoesophageal Fistula. J Pediatr Gastroenterol Nutr
10. Rajmil L, Perestelo-Perez L, Herdman M. Quality of life and rare diseases. Adv Exp Med Biol
11. Dellenmark-Blom M, Chaplin JE, Gatzinsky V, et al. Health-related quality of life among children, young people and adults with esophageal atresia: a review of the literature and recommendations for future research. Qual Life Res
12. Gibreel W, Zendejas B, Antiel RM, et al. Swallowing dysfunction and quality of life in adults with surgically corrected esophageal atresia/tracheoesophageal fistula as infants: forty years of follow-up. Ann Surg
13. Holscher AC, Laschat M, Choinitzki V, et al. Quality of life after surgical treatment for esophageal atresia: long-term outcome of 154 patients. Eur J Pediatr Surg
14. Svoboda E, Fruithof J, Widenmann-Grolig A, et al. A patient led, international study of long term outcomes of esophageal atresia: EAT 1. J Pediatr Surg
15. Legrand C, Michaud L, Salleron J, et al. Long-term outcome of children with oesophageal atresia type III. Arch Dis Child
16. Peetsold MG, Heij HA, Deurloo JA, et al. Health-related quality of life and its determinants in children and adolescents born with oesophageal atresia. Acta Paediatr
17. Dingemann C, Meyer A, Kircher G, et al. Long-term health-related quality of life after complex and/or complicated esophageal atresia in adults and children registered in a German patient support group. J Pediatr Surg
18. Lepeytre C, De Lagausie P, Merrot T, et al. Medium-term outcome, follow-up, and quality of life in children treated for type III esophageal atresia. Arch Pédiatr
19. Bal HS, Sen S, Karl S, et al. An assessment of quality of life of operated cases of esophageal atresia in the community. J Indian Assoc Pediatr Surg
20. US Department of Health and Human Services Food and Drug Administration. Guidance for industry: patient-reported outcome
measures: use in medical product development to support labeling claims. US: Center for Drug Evaluation and Research (CDER) Center for Biologics Evaluation and Research (CBER) Center for Devices and Radiological Health (CDRH); 2009. Available at: http://www.fda.gov/downloads/Drugs/Guidances/UCM193282.pdf
Accessed November 5, 2017.
21. Ruther A, Elstein D, Wong-Rieger D, et al. Aspects of patient reported outcomes in rare diseases: a discussion paper. Int J Technol Assess Health Care
22. Yang YF, Dong R, Zheng C, et al. Outcomes of thoracoscopy versus thoracotomy for esophageal atresia with tracheoesophageal fistula repair: a PRISMA-compliant systematic review and meta-analysis. Medicine (Baltimore)
23. Liu J, Yang Y, Zheng C, et al. Surgical outcomes of different approaches to esophageal replacement in long-gap esophageal atresia: a systematic review. Medicine (Baltimore)
24. Haverman L, Limperg PF, Young NL, et al. Paediatric health-related quality of life: what is it and why should we measure it? Arch Dis Child
25. Dellenmark-Blom M, Chaplin J, Gatzinsky V, et al. Health-related quality of life experiences among children and adolescents born with esophageal atresia: development of a condition-specific questionnaire for pediatric patients. J Pediatr Surg
26. Dellenmark-Blom M, Abrahamsson K, Quitmann JH, et al. Development and pilot-testing of a condition-specific instrument to assess the quality-of-life in children and adolescents born with esophageal atresia. Dis Esophagus
27. Matza LS, Patrick DL, Riley AW, et al. Pediatric patient-reported outcome
instruments for research to support medical product labeling: report of the ISPOR PRO good research practices for the assessment of children and adolescents task force. Value Health
28. Benjamin K, Vernon MK, Patrick DL, et al. Patient-reported outcome
and observer-reported outcome assessment in rare disease clinical trials: an ISPOR COA Emerging Good Practices Task Force Report. Value Health
29. Wild D, Grove A, Martin M, et al. Principles of good practice for the translation and cultural adaptation process for patientreported outcomes (PRO) measures. Value Health
30. Dellenmark-Blom M. Patient-reported Outcomes in Children and Adolescents Born With Esophageal Atresia: Condition-specific Aspects of Health-related Quality of Life and Coping. Diss. Gothenburg: University of Gothenburg; 2017.
31. Varni JW, Seid M, Kurtin PS. PedsQL™ 4.0: reliability and validity of the Pediatric Quality of Life Inventory™ version 4.0 generic core scales in healthy and patient populations. Med Care
32. The, DISABKIDS Group Europe. The DISABKIDS Questionnaires: Quality of Life Questionnaires for Children With Chronic Conditions Handbook. Lengerich, Germany: Pabst Science Publishers; 2011.
33. Simeoni MC, Schmidt S, Muehlan H, et al. Field testing of a European quality of life instrument for children and adolescents with chronic conditions: the 37-item DISABKIDS Chronic Generic Module. Qual Life Res
34. Kleinman L, Nelson S, Kothari-Talwar S, et al. Development and psychometric evaluation of 2 age-stratified versions of the Pediatric GERD Symptom and Quality of Life Questionnaire. J Pediatr Gastroenterol Nutr
35. Terwee CB, Bot SD, de Boer MR, et al. Quality criteria were proposed for measurement properties of health status questionnaires. J Clin Epidemiol
36. Koo TK, Li MY. A guideline of selecting and reporting intraclass correlation coefficients for reliability research. J Chiropr Med
37. Björk J. Praktisk statistik för medicin och hälsa. Stockholm: Liber; 2011.
38. Sullivan GM, Feinn R. Using effect size-or why the p value is not enough. J Grad Med Educ
39. Varni JW, Kay MT, Limbers CA, et al. PedsQL gastrointestinal symptoms module item development: qualitative methods. J Pediatr Gastroenterol Nutr
40. Varni JW, Bendo CB, Denham J, et al. PedsQL gastrointestinal symptoms module: feasibility, reliability, and validity. J Pediatr Gastroenterol Nutr
41. Franciosi JP, Hommel KA, Bendo CB, et al. PedsQL eosinophilic esophagitis module: feasibility, reliability, and validity. J Pediatr Gastroenterol Nutr
42. Cunningham C, Cho E, Shaffer ML, et al. Screening for psychosocial and family risk in pediatric gastrointestinal disorders. J Pediatr Gastroenterol Nutr
43. Dellenmark-Blom M, Chaplin JE, Jönsson L, et al. Coping strategies used by children and adolescents born with esophageal atresia—a focus group study obtaining the child and parent perspective. Child Care Health Dev
44. Chetcuti P, Phelan PD. Gastrointestinal morbidity and growth after repair of oesophageal atresia and tracheo-oesophageal fistula. Arch Dis Child
45. Raat H, Landgraf JM, Bonsel GJ, et al. Reliability and validity of the child health questionnaire-child form (CHQ-CF87) in a Dutch adolescent population. Qual Life Res
46. Pini Prato A, Carlucci M, Bagolan P, et al. A cross-sectional nationwide survey on esophageal atresia and tracheoesophageal fistula. J Pediatr Surg