Journal of Pediatric Gastroenterology & Nutrition:
Original Articles: Gastroenterology
Interobserver Variability in the Interpretation of Colon Manometry Studies in Children
Sood, Manu R.*; Mousa, Hayat†; Tipnis, Neel*; Di Lorenzo, Carlo†; Werlin, Steven*; Fernandez, Sergio†; Liem, Olivia†; Simpson, Pippa‡; Rudolph, Colin*
*Department of Pediatrics, Division of Gastroenterology, Medical College of Wisconsin, Milwaukee, WI
†Department of Pediatrics, Division of Gastroenterology, Nationwide Children Hospital, Ohio State University, Columbus, OH
‡Department of Quantitative Health Science, Children's Research Institute, Medical College of Wisconsin, Milwaukee, WI.
Address correspondence and reprint requests to Manu R. Sood, Associate Professor, Department of Pediatrics, Division of Gastroenterology, Medical College of Wisconsin, Milwaukee, WI 53045 (e-mail: Msood@mcw.edu).
Received 19 November, 2010
Accepted 16 May, 2011
The authors report no conflicts of interest.
Objectives: The aim of the present study was to evaluate the variability in interpretation of colon manometry (CM) in children.
Methods: Fifty-seven colon motility studies were independently reviewed by 5 observers. Each observer was required to report on the colonic motility during fasting, after administration of a meal, and after bisacodyl stimulation. They were also asked to comment whether CM study was normal or abnormal and whether in their opinion the postprandial recording provided clinically useful information.
Results: The median (range) agreement regarding the presence of high-amplitude propagating contractions (HAPC) was 83% (80%–92%). The interpretation of gastrocolonic response produced the most inconsistent results with median (range) agreemnet of 64% (53%–95%). The postprandial period was reported to be useful in only 3% to 24% of the studies. The median (range) agreement regarding the overall interpretation of the study being either normal or abnormal was 87% (83%–90%).
Conclusions: The most easily recognizable contraction pattern during CM is the high-amplitude propagating contractions. Visual interpretation of the gastrocolonic response produces the most inconsistent results and maximum variability. Abbreviated CM studies without the postprandial period or routine calculation of the motility index to evaluate gastrocolonic response can help make colon manometries more objective and reliable.
Constipation affects up to 3% of preschool and 1% to 2% of school-age children (1–3). The vast majority of children have functional constipation and require no or minimal investigative work up (4). In about one third of the patients, the disorder runs a more protracted course with one or more relapses (5). Patients with chronic intractable constipation can have abnormalities affecting the anal sphincter, disorders of stool expulsion, or slow colonic transit. It can sometimes be difficult to clinically differentiate between these disorders, and investigations including anorectal manometry, evaluation of colon transit time, and colon manometry (CM) can help clinical decision making (6–13). CM helps to differentiate functional constipation from colon neuromuscular problems and to plan surgical interventions in children with chronic intractable constipation, (9,14,15). Diagnostic criteria and guidelines for minimal standards for performing CM in children have been published (16).
CM studies require interpretation of a complex visual bowel motility pattern and are subject to interpretation bias. In other disciplines requiring interpretation of complex visual data, such as radiology, identifying areas of maximal inter-observer variability have led to modification of diagnostic criteria and to increased reliability (17,18). The objective of this study was to assess inter-observer variability in the interpretation of CM studies. We hypothesized that the inter-observer variability will be less for objective criteria, such as the presence of high-amplitude propagating contractions (HAPC) and more for subjective assessments such as gastrocolonic response and the final diagnosis.
We selected CM studies that were performed for the evaluation of children with chronic intractable constipation and fecal incontinence between 2002 and 2005. We included studies that were performed for clinical indications and the recording included the fasting period, postprandial period, and response to bisacodyl stimulation. We excluded studies that did not meet the above criteria or there was excessive amount of movement artifact to make the study difficult to interpret. A pediatric gastroenterologist identified 60 studies; 3 studies were excluded because the above criteria were not satisfied. All of the studies were made anonymous and each observer independently reviewed the manometry study without conferring with the other 4 observers. Each observer reported whether he/she could identify HAPC and any abnormal findings during the fasting and postprandial period. They were also required to comment if they observed the increase in colonic contractions following the meal suggestive of the presence of the gastrocolonic response and of a normal effect of bisacodyl stimulation. All 5 observers also were required to evaluate whether the CM study was normal or abnormal and whether they felt that the postprandial portion of the recording provided clinically useful information and influenced their decision making.
During the CM study, we aimed to provide 25% of the recommended daily energy intake for weight by meal. All of the drugs known to affect the gastrointestinal motility were discontinued at least 72 hours before the study. Patients fasted for at least 8 hours and colonoscopy was performed to place the manometry catheter and position confirmed by fluoroscopy. The motility study was performed about 2 hours after catheter placement. A water-perfused manometry catheter with 8 recording sites was used.
The data were analyzed using SPSS software, version 10 for Windows (SPSS Inc, Chicago, IL). We performed κ statistic but because the margins were imbalanced in several cases, even when there was agreement between 42/44 cases, a negative κ was obtained that did not summarize the agreement fairly. If the probability of disagreement is nonzero, the maximum value of κ decreases as the marginals deviate from a uniform distribution (19). We therefore decided to report the results as percentage agreement and considered the values between 90% and 100% to indicate excellent agreement, 80% and 89% good agreement, 70% and 79% fair agreement, and values below 70% were considered to show poor agreement. The study was approved by the institutional review board at Children's Hospital of Wisconsin and Nationwide Children Hospital.
Agreement on Major Categories
The demographic and years of experience of the 5 observers are summarized in Table 1. The percentage agreement between the 5 observers for specific observation of CM study is shown in Table 2. We found that the best agreement among the 5 observers was for an abnormal contraction pattern during the fasting phase of the CM study, followed by observation of HAPC during fasting study, differentiation between normal or abnormal CM study, and recognizing HAPC following bisacodyl stimulation.
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.
Response to Bisacodyl Stimulation
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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colon manometry; constipation; fecal incontinence
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