More Art Than Science: Impedance Analysis Prone to Interpretation Error

Background: Impedance monitoring for reflux evaluation does not have standardized scoring, which can confound interpretation between observers. We investigated the variability of impedance testing interpretation between physicians and computer software.

Methods: Raw impedance data from 38 patients that underwent impedance monitoring at a tertiary referral center between 2008 and 2013 were collected. Two physicians and computer software each analyzed the same impedance dataset for reflux activity and symptom-reflux correlation.

Results: Normalized reflux activity interpretations did not differ between physicians and the computer for acid or non-acid reflux. However, for weakly acidic reflux, there was significant difference between physicians (p < 0.01) and between physician and computer (p < 0.01). In analyzing all reflux, significant variability existed between physicians (p < 0.01) but not between physician and computer. Variability in interpretation altered diagnosis in 24 % of patients when comparing between physicians, 18 % of patients when comparing both physicians to the computer, and an additional 24 % of cases when comparing a single physician to the computer. Symptom-reflux correlation differed in 7 % of physician-physician comparisons versus 8 % of computer-physician comparisons.

Conclusion: Impedance testing analysis is subject to marked variability between physicians and computer software, making impedance prone to interpretation error that can lead to differences in diagnosis and management.