Objective: Completeness of lower esophageal sphincter relaxation, a parameter used to establish the diagnosis of achalasia, is an important manometric determination. This study compared four analysis methods that use point-pressure measurements to determine their relative accuracy and the best threshold values for incomplete relaxation.
Methods: Analyses were performed on 153 manometric studies that employed a 21-lumen catheter with pressure recording sites spaced at 1-cm intervals. Lower sphincter relaxation was measured from most appropriate sites as the 1) lowest residual pressure within 5 s of swallowing, 2) lowest residual pressure across the entire postdeglutitive period, 3) lowest mean residual pressure over a floating 3-s interval after swallowing, and 4) mean transsphincteric esophagogastric gradient extracted from a combination of conventional and topographic manometric information. Intragastric baseline pressures were taken both from the pull-through maneuver and from concurrent intragastric recordings, and methods were compared by their receiver operating characteristics.
Results: Best threshold values for segregating achalasia from nonachalasic controls differed across methods and depended on presence or absence of peristalsis in the comparison group. Transsphincteric gradient measurement had high sensitivity (> or = 0.94) and specificity (> or = 0.98) for achalasia irrespective of comparison group and was superior to all other methods. The 3-s mean residual pressure demonstrated greatest discriminant capabilities of the remaining conventional methods, which were modestly improved with concurrent measurement of intragastric pressure.
Conclusions: Analyses that average postdeglutitive pressures are superior to isolated nadir values in correctly discerning incomplete lower sphincter relaxation. The transsphincteric gradient is a novel approach for measuring sphincter relaxation, is unaffected by sphincter asymmetry and axial movement, and has the best receiver operating characteristics using point-pressure sensors.