Pressure-Less Acoustic Immittance-Derived Middle Ear Resonance Frequency: Repeatability and Comparison with Multifrequency Tympanometry

Background/Objectives: This study evaluated the intra-session repeatability, reliability, and clinical consistency of resonance frequency derived from pressure-less acoustic immittance (PLAI), and compared the results with those obtained using conventional multifrequency tympanometry under identical clinical conditions. Methods: In this pilot methodological comparison study, resonance frequency (RF) measurements were obtained in 15 subjects (30 ears) using multifrequency tympanometry (MFT) and pressure-less acoustic immittance (PLAI). Three consecutive measurements were performed for each ear using both methods. Agreement between methods was evaluated using Bland–Altman analysis. Within-method repeatability was assessed using range, coefficient of variation, repeatability coefficient, and intraclass correlation coefficients. Results: PLAI demonstrated lower intra-session variability than MFT. The mean within-series SD was 96.6 Hz for MFT and 10.5 Hz for PLAI. The coefficient of variation was 9.3% for MFT and 3.2% for PLAI, while intraclass correlation coefficients were 0.60 and 0.83, respectively. The repeatability coefficient was ±367 Hz for MFT and ±47 Hz for PLAI. Bland–Altman analysis revealed a systematic difference between the two methods, with a mean bias of 580.7 Hz and 95% limits of agreement between 247.5 Hz and 913.9 Hz, indicating that the two methods are not interchangeable. Conclusions: PLAI demonstrated higher repeatability than MFT. Its lower variability may support a more consistent clinical interpretation; PLAI-derived RF may therefore represent a stable method-specific parameter for middle ear assessment. However, RF values should be interpreted within method-specific frameworks.