Balloon Expulsion Test Does Not Seem to Be Useful for Screening or Exclusion of Dyssynergic Defecation as a Single Test

BACKGROUND/AIMS: Balloon expulsion test (BET) is regarded as a screening tool of dyssynergic defecation (DD). However, some patients with normal BET results may be treated effectively by biofeedback training. This study aims to validate BET as a single screening test. METHODS: Two hundred and thirty-two patients who were diagnosed with functional constipation or irritable bowel syndrome with constipation who underwent anorectal manometry (ARM) and BET at Seoul National University Hospital were enrolled. We evaluated the validity of BET based on ARM and electromyography (EMG) during biofeedback training. RESULTS: If BET ≤ 1 minute was defined as normal, sensitivity and negative predictive value (NPV) of BET in predicting paradoxical contraction based on ARM findings were 71.4% and 13.9%. If BET ≤ 3 minutes was defined as normal, sensitivity and NPV were 35.2% and 6.6%. Specificity and positive predictive value (PPV) of BET ≤ 3 minutes criteria were 84.8% and 93.3%. Same analysis was conducted in 107 patients who underwent EMG during biofeedback training. With 1-minute criteria, sensitivity and NPV of BET were 70.3% and 14.3%. With 3 minutes criteria, sensitivity and NPV of BET was 38.6% and 8.8%. Specificity and positive predictive values were both 100.0%. CONCLUSIONS: Based on either ARM or EMG during biofeedback training, sensitivity was at most 71.4% and NPV was less than 15.0% irrespective of whether BET was within 1minute or within 3 minutes. BET seems to have a limitation as both a screening test for dyssynergic defecation and a simple assessment to rule out the necessity of biofeedback training.