A recent retrospective study (A Rengarajan et al. Clin Gastroenterol Hepatol 2020; 18: 589-95), with a cohort of 371 patients (mean age 54 years) shows how impedance testing may help identify patients who are likely to respond to reflux management when pH probe testing is equivocal. The cohort included adults with persistent reflux symptoms. Response to antireflux therapy was defined as >50% improvement in esophageal symptoms.
- 107 (28.8%) had pathologic acid exposure time (AET) (pH<4 for >6%)
- 234 (63.1%) had abnormal mean nocturnal baseline impedance (MNBI) (<2292 ohms). MNBI was calculated using baseline values at 10-minute periods between 1-3 am from the 5 cm channel to correspond to total distal AET.
- Figure 1, shows the combined use of AET and MNBI. Only 106/107 patients with AET>6, had an abnormal MNBI. In the borderline category of AET 4-6%, 62/68 (91.2%) had abnormal MNBI values. In those with AET <4, MNBI was abnormal in 66/196 (33.7%)
Response to Treatment:
- Among patients with AET >6, 66/89 (74%) responded to medical therapy and 18/23 (78%) responded to surgical therapy; among patients with AET 4-6%, 37/56 (66%) responded to medical therapy and 14/17 (82%) responded to surgical therapy. In those with AET <4, 39/185 (21%) responded to medical therapy and 16/23 (70%) responded to surgical therapy
- Among patients with a low MNBI, 119/198 (60%) responded to medical therapy and 41/50 (82%) to surgical therapy. In those with a normal MNBI, 23/132 (17%) responded to medical therapy and 7/13 (54%) responded to surgical treatment
- In those with AET >6, 84/111 (76%) responded to treatment. For those with AET 4-6%, of those with low MNBI, 49/67 (73%), responded (similar to those with AET >6%). In those with low MNBI and AET <4, 27/70 (39%) responded to treatment
- 28/138 (20.2%) with normal AET <4 and with normal MNBI responded to treatment
My take: The big takeaway is that all of our tests for pathologic reflux are highly flawed; impedance may (to a small degree) help stratify patients with equivocal evaluation based on AET. Normal tests do not exclude response treatment (especially surgery).
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