A Newly Developed Metric, PSDrest Predicts the Presence of Defecatory Disorders and Highly Correlates with the Balloon Expulsion Test
Tengku Ahmad Iskandar Tengku Alang1,2, Lee Yeong Yeh1,2, Khairil Khuzaini Zulkifli3, Mung Seong Wong1,2, Nor Aslina Abd Samat1,2, Siti Norhasliza Muhamad1,2, Azliani Abd Aziz1,2,
1School of Medical Sciences, Universiti Sains Malaysia, Kota Bharu, Kelantan, Malaysia.
2Hospital Universiti Sains Malaysia, Health Campus, Universiti Sains Malaysia, Kota Bharu, Malaysia.
3Gastrenterology Unit, Faculty of Medicine, Universiti Teknologi MARA, Sungai Buloh, Selangor, Malaysia
1School of Medical Sciences, Universiti Sains Malaysia, Kota Bharu, Kelantan, Malaysia.
2Hospital Universiti Sains Malaysia, Health Campus, Universiti Sains Malaysia, Kota Bharu, Malaysia.
3Gastrenterology Unit, Faculty of Medicine, Universiti Teknologi MARA, Sungai Buloh, Selangor, Malaysia
Background: In defecatory disorder, there is poor correlation between conventional manometry parameters and balloon expulsion test (BET) and therefore new metric is needed. We aimed to develop a new metric from resting anal pressure based on the Fourier transform tool, to validate the new metric and to correlate the metric with BET.
Methods: Consecutive healthy participants and patients with defecatory disorders (Rome IV) were recruited after informed consent. All underwent high resolution 6-channel solid state anorectal manometry (Laborie, Mississauga, Canada) and BET. Resting pressure profiles were converted into ASCII files and analyzed using MATLAB program (VR2010b, The MathWorks, Natick, USA). A new metric, Power Spectral Densityrest (PSDrest, unit V/√Hz) was developed using the Fourier transform tool. The ideal cut-off level of PSDrest was determined using ROC analysis, and its correlations with defecation index (DI) and BET were analyzed using Pearson correlation analysis, with P<0.05 as significant.
Results: 8 normal (mean age 22.8 years) and 16 constipated (mean age 51 years) females were analyzed. Of 16 constipated females, 8 had normal BET (< 1 min) and 8 with abnormal BET (≥ 5 min). Those with constipation vs. normal reported lower PSDrest (mean 0.58 vs. 0.88, P=0.05). Based on the ROC analysis, PSDrest cut-off value < 0.5 V/√Hz can accurately differentiate constipation from normal with an area under the curve (AUC) of 0.97 (95% CI 0.89-1.05, P=0.04), sensitivity 100%, specificity 88%, positive predictive value 89% and negative predictive value 100%. Among constipated individuals, PSDrest was correlated with BET (R=0.81, P<0.001) but not DI (P=0.14). No correlation was seen between BET and DI (P=0.3).
Conclusion: A PSDrest value < 0.5 V/√Hz predicts the presence of defecatory disorder and is highly correlated with abnormal BET. Further validation study in larger cohort is required.