Singh P, Taylor R H, Colin-Jones D G
Department of Gastroenterology, Queen Alexandra Hospital, Portsmouth.
Gut. 1994 Mar;35(3):304-8. doi: 10.1136/gut.35.3.304.
For oesophageal pH monitoring, the pH probe is usually positioned 5 cm above the lower oesophageal sphincter (LOS). This is by convention, and has not been compared with other positions in its ability to discriminate between physiological and abnormal acid reflux. Using simultaneous two level 24 hour pH monitoring (5 and 10 cm above manometrically determined LOS) in 31 controls and 51 patients with reflux oesophagitis, the significance of the precise position of the probe in the oesophagus was examined. Secondly, this study compared the discrimination between the two groups achieved at the two levels. Patients had greater acid exposure than controls at both levels. In controls, acid exposure was greater at distal than at the proximal level except the supine acid exposure, which was similar at both levels. In patients, acid exposure was greater at the distal level for all variables (median % of total time pH < 4 = 11.7 v 7.6; p = 0.001). There was excellent correlation between the two levels for all variables in controls (r = 0.883, 0.935, 0.813, and p < 0.001 for percentage of time pH < 4 for total, supine, and upright times) as well as in patients (r = 0.848, 0.848, 0.779, and p < 0.001). On discriminant and receiver operating characteristic analysis, pH threshold 4 seemed as good as or better than other pH thresholds in discriminating between controls and patients. The percentage of total time pH below 4 seemed to discriminate as well or better than other variables at both levels. The distal level (5 cm above LOS) provided slightly better discrimination than proximal level (10 cm) (percentage of subjects correctly classified=81.7 v 75.6). The critical factor for the reliability of the test is not the precise position of the pH probe relative to the LOS, but that the same position is consistently used in patients and controls.
对于食管pH监测，pH探头通常置于食管下括约肌（LOS）上方5厘米处。这是惯例做法，且尚未就其区分生理性和异常酸反流的能力与其他位置进行比较。在31名对照者和51名反流性食管炎患者中，采用同步双水平24小时pH监测（在测压确定的LOS上方5厘米和10厘米处），研究了探头在食管中精确位置的意义。其次，本研究比较了在两个水平上两组之间的区分情况。在两个水平上，患者的酸暴露均多于对照者。在对照者中，除仰卧位酸暴露在两个水平相似外，远端水平的酸暴露多于近端水平。在患者中，所有变量在远端水平的酸暴露均更多（pH<4的总时间中位数百分比=11.7对7.6；p=0.001）。对照者和患者中所有变量在两个水平之间均具有极好的相关性（总时间、仰卧位时间和直立位时间pH<4的时间百分比的r分别为0.883、0.935、0.813，p<0.001）以及（r=0.848、0.848、0.779，p<0.001）。在判别分析和受试者工作特征分析中，pH阈值4在区分对照者和患者方面似乎与其他pH阈值一样好或更好。pH低于4的总时间百分比在两个水平上的区分能力似乎与其他变量一样好或更好。远端水平（LOS上方5厘米）比近端水平（10厘米）的区分能力略好（正确分类的受试者百分比=81.7对75.6）。该测试可靠性的关键因素不是pH探头相对于LOS的精确位置，而是患者和对照者始终使用相同的位置。
