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Determining the anal position index in Portuguese newborns: Is it a consistent and reproducible measurement?
Luís Trigueiros da Cunha1, Luísa Gaspar2, Cármen Carvalho3
1Instituto Ciências Biomédicas Abel Salazar, R. de Jorge de Viterbo Ferreira 228, 4050-313 Porto, Portugal.
Background:
The anatomical position of the anus is a critical parameter in neonatal physical assessment due to its association with functional symptoms like constipation and anatomical anomalies such as anorectal malformations (ARM). The Anal Position Index (API) provides an objective and useful method for assessing anal positioning, though normal values for Portuguese newborns remain undocumented. We aimed to determine normal API values in Portuguese full-term newborns and assess interobserver variability.
Methods:
This prospective, cross-sectional observational study included 201 healthy, full-term Portuguese newborns. Measurements were obtained using anatomical landmarks extensively described in the literature. API was calculated as the ratio of perineal distances specific to each gender. Interobserver reliability was assessed in a subset of 31 newborns.
Results:
The mean API was 0.37 ± 0.08 in females and 0.52 ± 0.08 in males, significantly higher in this gender (p < 0.001). No significant correlation was found between API and anthropometric parameters. Interobserver reliability demonstrated good agreement (ICC = 0.879, p < 0.001).
Conclusions:
Our study defined normal API values for Portuguese newborns, consistent with results from previous investigations. API measurements showed high reliability and reproducibility, making it a simple, non-invasive tool for transversal use in neonatal examination for anomalies of anal positioning. Further multicenter, longitudinal studies are recommended to validate its clinical significance and utility in routine pediatric care.
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