A questionnaire that can measure disease severity from the patients perspective in patients with pectus excavatum already exists in English (Pectus Excavatum Evaluation Questionnaire; PEEQ). This questionnaire was recently translated into Dutch. Before this Dutch version can be used, it needs to be tested by a number of patients.
Data will be collected at three moments:
1. Preoperatively: The PEEQ will be completed on paper during the outpatient clinic visit. 2. Postoperatively: The PEEQ will be completed electronically 2 months post-surgery. 3. Test-retest reliability: The PEEQ will be administered electronically at least two weeks after a previous assessment.
Eligible participants will be pectus excavatum patients aged 12 to 18 years old who are scheduled for a Nuss procedure. Parents or legal guardians will also be invited to complete the parent section of the PEEQ.
Exclusion criteria will be the inability of the patient or their parent/guardian to complete the corresponding section of the questionnaire due to language barriers.
Participants will be identified and enrolled during their preoperative visit at the outpatient clinic of Zuyderland Medical Center by a member of the research team.
Cohort
Prospective
Not listed
Structural validity
A Kaiser-Meyer-Olkin (KMO) test and Bartlett's test of sphericity are performed to assess the adequacy of patient sampling before performing further structural tests. Threshold values of ≥ 0.70 in KMO test and p \< 0.05 in Bartlett's test of sphericity indicate the suitability of the collected data for factor analysis (6,7). Exploratory factor analysis (EFA), using principal axis factoring and a promax rotation method, will be conducted to identify the underlying factor structure for both the child and parent sections (8,9). These factor structures will later be subjected to confirmatory factor analysis (CFA), using polychoric correlations and robust maximum likelihood estimation, to evaluate the validity of the structures derived from EFA (8,10). Within EFA, the Kaiser criterion (eigenvalue \> 1), explained variance (≥50%), and interpretability principle will be applied to determine the number of factors to be retained. Squared multiple correlations are used to compute the communality
Internal consistency
Cronbach's alpha coefficient, a measure of internal consistency, will be calculated for each subscale. A value \> .70 indicates sufficient reliability of the questionnaire for application at the group level, while a value \> .90 implies suitability for individual assessment
Test-retest reliability
Test-retest reliability for each subscale will be evaluated using a two-way mixed-effects model for the intraclass correlation coefficient (ICC), type (3.1), with 95% confidence intervals reported (CI) (15). The strength of agreement will be interpreted following the guideline provided by Cicchetti (1994) (16): \< 0.40 = poor, 0.40-0.59 = fair, 0.60-0.74 = good, 0.75-1.00 = excellent. For individual items, quadratic weighted Cohen's kappa will be calculated along with its 95% to identify problematic items, with interpretation based on the standards proposed by Landis and Koch (1977) (17): \<0 = poor, 0.01-0.20 = slight, 0.21-0.40 = fair, 0.41-0.60 = moderate, 0.61-0.80 = substantial, and 0.81-.001 = almost perfect.
Responsiveness
The responsiveness of the questionnaire will be determined using the construct approach in which preoperative and postoperative scores are compared using a paired t-test or Wilcoxon signed-rank test for skewed data. The effect size will be expressed in Cohen's d and is calculated as the mean difference divided by the standard deviation of the difference. We hypothesize that the total score on the PEEQ and mean scores per subscale improve after surgical correction of the pectus excavatum deformity as demonstrated by the original questionnaire (2,3). Responsiveness of individual items will be evaluated using a paired t-test or Wilcoxon signed-rank test, as appropriate, to guide further item refinement.
Floor and ceiling effects
The floor and ceiling effects will be assessed by calculating the proportion of participants scoring the lowest or highest possible scores. Effects are considered substantial if \> 15% of the participants score at the extremes for a specific item or subscale (18).
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Erik de Loos
Lead sponsor
Zuyderland Medisch Centrum
Sponsor institution
