Article
Similar artefact susceptibility for water- and air-filled urodynamic systems: a non-inferiority randomized controlled trial
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Published: | November 20, 2024 |
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Introduction: Urodynamic investigation (UDI) is the gold standard to assess refractory lower urinary tract symptoms. Water-filled systems (WFS) are the method of choice for UDI pressure measurements according to the International Continence Society (ICS). However, air-filled systems (AFS) are widely used as convenient alternative to WFS, although it is unclear whether these systems produce comparable measurements.
Methods: From April 2021 to January 2022 patients (n=490) undergoing UDI at the Department of Neuro-Urology, Balgrist University Hospital Zurich Switzerland, were included in this randomized controlled non-inferiority trial. Inclusion criteria were age >18yr with competent German language skills who gave informed consent and suffer lower urinary tract symptoms (LUTS).
The patients were allocated by block randomization in a 1:1 ratio to undergo UDI using a WFS (n=244) or an AFS (n=246). UDI consisted of same session repeat filling cystometry and pressure flow study. A telephone follow up was performed 7-14 days after the examination.
The primary endpoint was artefact susceptibility evaluated by a modified Bristol UTraQ quality scoring scale (ref) ranging from 0 to 18, with higher scores indicating a better quality. Urodynamic traces were assessed by an expert in functional urology blinded to the measurement system used. Patients and clinicians were not masked to the diagnostic assignments. A clinically meaningful non-inferiority margin was pre-specified as -2 points on the quality scoring scale (AFS-WFS).
Results: The median overall quality score was 14.5 points (Q1-Q3: 13.5-15.5) for the WFS and 15.5 (Q1-Q3: 14.5-16.5) for the AFS. Inferiority of AFS could be rejected at the pre-specified non-inferiority margin (0.96 (95% confidence interval 0.68-1.25, p<0.001). Typical artefacts consisted of repeated relevant (i.e., >5 cmH2O) rectal contractions (WFS vs AF: 57% (138/244) vs 68% (166/246), p=0.015), poor pressure transmission during cough test at empty bladder (WFS vs AFS: 38% (93/244) vs 4% (10/246), p<0,001), and detrusor resting pressure outside of the physiological range at empty bladder (i.e., >5cmH2O or <-5cmH2O) (WFS vs AFS 16% (40/2044) vs 42% (104/246), p<0.001). Overall, AFS revealed higher resting pressures at start of UDI (vesical pressure WFS vs AFS: 19.8±7.1 vs 26.1±8.4 cmH2O; abdominal pressure WFS vs AFS: 21.4±7.6 vs 30.7±9.2 cmH2O, p<0.001).
UDI installation time were similar between groups (WFS vs AFS: 27±7.6 vs 27.1±7.9 min, p=0.913).
Self-limiting pain (30%; 146/490), increased urgency (18%; 90/490), self-limiting macrohematuria (8%; 41/490), and urinary tract infections (6%; 28/490), were the most commonly reported examination-related adverse events (AE) during the follow-up interview 7-14 days after examination. Except for pain, which occurred significantly more often after using the AFS (p=0.014), AEs were similar between groups (p>0.18).
Conclusion: Our results demonstrate that AFS are non-inferior to WFS regarding overall quality of urodynamic traces. However, both measurement systems have particular pitfalls that need to be known for problem solving during UDI and require awareness for accurate interpretation of UDI.