Observers were unanimous in differentiation of normal and abnormal motility study in 69% of the cases. They were unwilling or reluctant to assign a diagnosis of a normal or abnormal study and used the “unsure” option in 9% of the studies. The levels of agreement varied between observer pairs, ranging from 66% to 95%. The results for CM interpretation for the 5 observers are shown in Table 3.
The observers showed good to excellent agreement for detecting abnormalities during the fasting study with a median agreement of 96% with a range of 90% to 98%. The agreement regarding HAPC during the fasting period was 92% with a range of 90% to 98%.
Interpretation of the postprandial period produced maximum variability and the least agreement among the 5 observers. Consensus was reached in only 19% of the studies and in 19% the observers were not sure or not willing to commit if there was meal-induced increase in colon contractions. The median agreement regarding the presence of a gastrocolonic response was 64%, with a range 53% to 95%. The median agreement regarding the occurrence of an abnormal motility pattern was 82%, range 70% to 88%. The observers reported that the postprandial period was useful and influenced their decision making in 3% to 24% of the studies (Table 4). The median agreement regarding the postprandial recording being useful or not in clinical decision making was 87% (range 83%–90%). The data regarding the meal consumed during CM were available in 48 subjects. The mean ± standard deviation percentage of the recommended daily energy intake provided by the meal during CM was 32 ± 16. Sixty-eight percent of the patients were able to eat sufficient amounts to meet the recommendation. Fifty percent of children younger than 5 years were not able to eat the recommended amount compared with 20% who were older than 5 years (P < 0.05). We did not find a significant relation between the energy consumed and each observer's decision regarding the presence or absence of gastrocolonic response. Although some patients consumed less than the recommended energy, it did not have a significant effect on the interpretation of gastrocolonic response by the 5 observers in our study.
The median agreement regarding presence or absence of HAPC following bisacodyl stimulation was 83% with a range of 80% to 92%. The consensus regarding HAPC following bisacodyl was reached in only 50% of the studies. The median agreement regarding the response to bisacodyl stimulation being normal or abnormal was 78% with a range of 71% to 91%.
Interpretation of complex visual data resulting in high interobserver variability has led to modification of diagnostic criteria and increased reliability (17,18). To improve acceptance of diagnostic tests and techniques used to evaluate motility disorders, methods of interpretation of these test must be validated. There are few studies that have attempted to assess interobserver variability in interpretation of manometry data (20–22). There have been attempts to compare computer-generated responses to teams of human observers in studies evaluating lower esophageal sphincter pressure (23,24); however, this approach is not possible when evaluating complex motility patterns, rather than defined changes in baseline sphincter pressure and relaxation with swallowing. Connor et al (21) reported variability in interpretation of antroduodenal manometry studies in children. They confirmed that there was greater agreement for measurement of a defined contractile event, such as the migrating motor complex than detection of these events. The visual evaluation of a motility pattern is a subjective assessment and likely to be influenced by personal bias. In the present study we found that detection and measurement of HAPC produced reasonably good agreement; however, interpretation of the gastrocolonic response, which requires a subjective evaluation of an increase in colonic contractions following a meal, produced the greatest variability. The 5 observers achieved consensus regarding gastrocolonic response in only 19% of the studies. Evaluation of the meal response on bowel motility in children can be difficult. Connor et al (21) also reported a greater variability in evaluating postprandial hypomotility during antroduodenal manometry and recommended that calculating the motility index may help to increase the reliability. A similar approach can be adopted for evaluation of gastrocolonic response.
Adult gastroenterologists have used a slightly different approach and used a barostat to measure changes in colonic wall tone following a meal, as an objective measure of gastrocolonic response (25). A similar approach adopted in children could remove the bias due to the subjective interpretation of gastrocolonic response; however, unlike adults, it is sometimes difficult to use a standardized meal during CM studies in children. Inadequate energy and fat intake may blunt the meal response and may make barostat-evaluated colonic wall tone change difficult to interpret as well.
The 5 observers were required to comment if they found the meal response useful in clinical decision making and if the postprandial response influenced their interpretation of the CM study. The observers reported that in 3% to 24% of the studies, the postprandial period provided useful information and affected their clinical decision making. It is possible that personal experience could have affected the observer's interpretation of the usefulness of gastrocolonic response. Observer who finds interpreting gastrocolonic response difficult in clinical practice may be more inclined to report that the gastrocolonic response is not useful in colon motility evaluation. Another factor that may influence the interpretation of the gastrocolonic response is the amount of energy consumed during the meal. Because it is difficult to use a standardized meal in children, another approach to improve agreement in evaluation of CM study is to perform an abbreviated study, which evaluate fasting colon motility for 60 minutes followed by bisacodyl stimulation.
In summary, HAPC are the most consistent and easily recognizable motility pattern during CM studies. The postprandial recording provides the most inconsistent results and was deemed not clinically helpful in the majority of studies. Future studies should evaluate whether using abbreviated CM studies without the postprandial period will suffice in clinical practice or the use of a barostat to assess changes in colon wall tension or calculation of the motility index to more objectively evaluate the gastrocolonic response will help make CM studies more objective and reliable.
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