Placement of pH-monitoring probes using height-related formulas. Is it an applicable method to adults?

Introduction Oesophageal pH-monitoring allows the quantification of gastric reflux episodes in patients with gastroesophageal reflux disease (GERD). The accuracy of the test depends on correct positioning of the pH sensor 5 cm above the lower oesophageal sphincter (LES). The most precise manner to locate the LES is through prior determination by oesophageal manometry. However, because this technique is uncomfortable, mathematical formulas tend to be used in children. Objectives To evaluate the applicability of paediatric formulas to estimate oesophageal length in adults and their effect on diagnostic accuracy. Material and methods A prospective study was carried out in adult patients, in whom the distance between the nasal orifice and the LES was determined by manometry and was compared with the estimated height-related distance calculated by four paediatric formulas (numbered 1–4). We also evaluated the relationship between the position of the probe and the percentage of reflux detected in our series of impedance measurements. Results Formula 1 (9.31 + height in cm × 0.197) was the most accurate (comparison of means −0.38 with 95% CI −0.70/−0.06, p = 0.019). With this formula, none of the patients had estimation errors of ±6 cm. With formulas 2, 3 and 4, the percentage of error was 4.4%, 1.5% and 32.0%, respectively. Conclusion Oesophageal length estimation in adults by using formula 1 is acceptable and can be used in adult patients who refuse to undergo prior manometry.