The results of this first randomized trial confirm that 24 hour pH-metry using unsedated peroral WC insertion is better tolerated than SC both overall and during placement. As expected, nasal and throat discomfort was prominent in the SC group, while chest discomfort was higher in the WC group during the pH monitoring period. Furthermore, in keeping with previous reports on WC, our findings suggest that the majority of patients undergoing WC would choose to continue their regular activities including employment, in contrast to SC where none reported being capable of working. Lastly, although WC is more costly than SC, our cost analysis shows that the extra expense of WC is partially offset when the higher patient and caregiver time costs of SC are considered.
Since SC and WC appear to be equally effective in diagnosis of abnormal reflux when the procedure is successful, failure rates thus become a key measure of effectiveness. The 12% overall failure rate of WC in the present study falls within the range of that reported in the literature [5
], although a recent series reported a failure rate of only 2% [20
]. The 5 WC failures that we encountered resulted from 2 capsule calibration errors (equipment failure), 1 patient who could not tolerate placement of the capsule (patient intolerance) and 2 early capsule detachments. Both of the WC early detachments occurred near the start of the trial. Although the investigators did have some prior experience with WC at the start of the study, it is certainly possible that the early detachments reflect the learning curve of the technique. However, it should also be noted that this study randomized patients prospectively which previous case series did not; since previous large series of WC did both endoscopic and unsedated transoral placements [10
], patients who felt unable to tolerate unsedated placement presumably opted for endoscopic placement with sedation. That approach will underestimate failure rates from a patient intolerance standpoint, and thus the approach used in this study is more applicable to situations where endoscopic placement is not available. Although this study was not designed to evaluate the 4
cm nose-to-mouth conversion factor determined by Lacy et al. [10
], there were no gross misplacements of WC judged either clinically or according to the pH study results using this method. Therefore, this relatively non-invasive technique is easy to learn and perform and is as reliable as SC for the ambulatory collection of esophageal pH data.
Placement of WC without need for direct visualization via gastroscopy is an important development. Endoscopy is resource intensive, carries risks to patients and the sedation that is generally required may alter the results during the first 24 hours of pH monitoring [9
]. Furthermore, patients can’t drive or work after receiving sedation, which increases the patient-borne costs of the procedure. We have shown that this is also a significant problem for SC given that none of the patients in the SC group reported being capable of going to work while the catheter was in place. While there are some motivated patients in the community who choose to work with a SC in place, these are a small minority. In contrast, over 90% of those in the WC group would have chosen to return to work.
The results of our cost analysis demonstrate that peroral WC (ESM
WC) is more costly than ESM
SC, but less expensive than WC placed via gastroscopy (EGD
WC). However, the incremental cost of ESM
WC over ESM
SC drops when one takes into consideration the increased patient and caregiver time costs associated with SC. When time costs were excluded the incremental cost of ESM
WC over ESM
SC was $243 compared to $108 when these costs were included. Furthermore, had our failure rate been only 5% instead of 12%, the incremental cost of ESM
WC over ESM
SC would be $85 instead of $108. Our post procedure questionnaire suggests that patients prefer WC over SC given that nearly 90% would agree to have it repeated if necessary compared to only half of those who received SC. Therefore, given that patients prefer WC, can continue their usual daily activities and can continue to work during the ambulatory testing period, the added cost of WC may be something that health jurisdictions should consider. Like many technologies, the cost may drop over time. We have shown that WC would be cost neutral if the cost of the device were dropped to $193.
Our study has a number of limitations. Although the study was powered to assess the overall patient experience with pH placement and 24–48 hours of testing, the sample size may have been too small to detect significant differences in infrequent secondary outcomes such as failure rates. However, the failure rates did match those in the literature, and were subjected to sensitivity analysis in the cost analysis. Second, the VAS scales used to assess discomfort have not been validated specifically for manometry or pH testing, and thus may not accurately capture all dimensions of the pH testing experience. They are, however, generally accepted measures for pain [15
], and have been used in the pH-metry literature previously [16
]. With regard to the cost analysis, the costing model was based on a number of assumptions which may not be accurate for all populations or situations. However, this is a feature of all cost analyses. To account for the uncertainty in our model estimates we performed sensitivity analyses to test how changes in our model inputs affected our results. Finally, we assumed that SC and WC have equivalent effectiveness for diagnosis of GERD. Typically, WC studies are performed for 48 hours in clinical practice, and this extra data may improve sensitivity for detection of abnormal acid exposure [5
]. However, there is no consensus as to whether this improves the effectiveness of the technology, but WC does not appear to be less sensitive than SC [5
]. We thus took a conservative approach based on the assumption that the technologies were equivalent.
The major limitation of WC pH-metry is the pH measurement from only one site. SC typically has a proximal pH sensor as well, which provides more data, although does not affect composite score calculation and subsequent determination of abnormal acid exposure. With the advent of new technologies such as multichannel intraluminal impedance with pH (MII-pH), even more data is available to analyze all refluxate regardless of pH. This becomes increasingly important in the post-proton pump inhibitor (PPI) era, where the majority of pH investigations are done for atypical symptoms or PPI failure. The exact role of WC pH-metry in the stable of diagnostic tools for reflux disorders has yet to be fully determined, but will likely be the modality of choice for confirmation of acid reflux, for example prior to fundoplication.