How Best To Estimate Insertion Length of Multichannel Intraluminal Impedance-pH Probes in Children.

OBJECTIVE: To assess the reliability of the KidZ Health Castle formula (KHC-F) to determine the correct probe position of a multichannel intraluminal impedance pH (MII-pH).

STUDY DESIGN: A retrospective cohort study was performed on 222 children between 1 month and 18 years old undergoing MII-pH. Primary outcome was the comparison of the pH-sensor location determined by the KHC-F with the radiological target position. Margin of error was defined as one centimeter from target position. Performance of the KHC-F and existing formulas was determined via the percentage with a correct position, mean error, 95% limits of agreement (Bland Altman plots) and Spearman correlation. Post hoc analysis was performed with an updated KHC-F v2, subtracting -0.5cm from the KHC-F.

RESULTS: Positioning with KHC-F was correct in two thirds of the participants, with a very strong correlation (ρ 0.91) with the target position. Bland Altman plots showed good agreement between KHC-F and target position (mean error of -0.44cm, lower limit -3.2cm, upper limit 2.3cm). Post hoc analysis with KHC-F v2 showed a correct positioning in 74%. Comparison with other formulas showed a stronger performance of KHC-F and KHC-F v2 on correct positioning, mean error and 95% limits of agreement.

CONCLUSIONS: The KHC-F leads to reliable results. KHC-F v2 outperforms all other existing formulas in children, thereby reducing the need for repositioning and the amount of x-ray exposure. The age distribution of the sample may be a limitation as well as the retrospective nature of the study.