Development of a multidimensional measure for recurrent abdominal pain in children: population-based studies in three...

Recurrent abdominal pain (RAP) is a common problem in children and adolescents. Evaluation and treatment of children with RAP continue to challenge physicians because of the lack of a psychometrically sound measure for RAP. A major obstacle to progress in research on RAP has been the lack of a biological marker for RAP and the lack of a reliable and valid clinical measure for RAP. The objectives of this study were (1) to develop and test a multidimensional measure for RAP (MM-RAP) in children to serve as a primary outcome measure for clinical trials, (2) to evaluate the reliability of the measure and compare its responses across different populations, and (3) to examine the reliabilities of the measure scales in relation to the demographic variables of the studied population.

We conducted 3 cross-sectional studies. Two studies were clinic-based studies that enrolled children with RAP from 1 pediatric gastroenterology clinic and 6 primary care clinics. The third study was a community-based study in which children from 1 elementary and 2 middle schools were screened for frequent episodes of abdominal pain. The 3 studies were conducted in Houston, Texas. Inclusion criteria for the clinic-based studies were (1) age of 4 to 18 years; (2) abdominal pain that had persisted for 3 or more months; (3) abdominal pain that was moderate to severe and interfered with some or all regular activities; (4) abdominal pain that may or may not be accompanied by upper-gastrointestinal symptoms; and (5) children were accompanied by a parent or guardian who was capable of giving informed consent, and children over the age of 10 years were capable of giving informed assent. The community-based study used standardized questionnaires that were offered to 1080 children/parents from the 3 participating schools; 700 completed and returned the questionnaires (65% response rate). The questionnaire was designed to elicit data concerning the history of abdominal pain or discomfort. A total of 160 children met Apley's criteria and were classified as having RAP. Inclusion criteria were identical to those criteria for the clinic-based studies. Participating children in the 3 studies received a standardized questionnaire that asked about socioeconomic variables, abdominal pain (intensity; frequency; duration; nature of abdominal pain, if present, and possible relationships with school activities; and other upper gastrointestinal symptoms). We used 4 scales for the MM-RAP: pain intensity scale (3 items), nonpain symptoms scale (12 items), disability scale (3 items), and satisfaction scale (2 items). Age 7 was used as a cutoff point for the analysis as the 7-year-olds have been shown to exhibit more sophisticated knowledge of illness than younger children.

A total of 295 children who were aged 4 to 18 years participated in the study: 155 children from the pediatric gastroenterology clinics, 82 from the primary care clinics, and 58 from the schools. The interitem consistency (Cronbach's coefficient alpha) for the pain intensity items, nonpain symptoms items, disability items, and satisfaction items were 0.75, 0.81, 0.80, and 0.78, respectively, demonstrating good reliability of the measure. The internal consistencies of the 4 scales did not significantly differ between younger (< or =7 years) and older (>7 years) children. There was also no significant variation in the coefficient alpha of each of the 4 scales in relation to gender or the level of the parent's education. Reliability was identical for the pain-intensity items (0.74) among children who sought medical attention from primary care or pediatric gastroenterology clinics. The intercorrelations of factor scores among the 4 scales showed a strong relationship among the factors but not high enough that correlations would be expected to be measuring the same items. The results of the factor analysis identified 5 components instead of 4 components representing the 4 scales. The 12 items of the nonpain symptoms scale were classified into 2 components; 1 component included heartburn, burping, passing gas, bloating, problem with ingestion of milk, bad breath, and sour taste (nonpain symptoms I), and the other included nausea/vomiting, diarrhea, and constipation (nonpain symptoms II). The program ordered the 5 components on the basis of the percentage of the total variance explained by each component and consequently by the strength of each components in the following order: nonpain symptoms I, pain intensity, pain disability, satisfaction, and nonpain symptoms II. Of the 20 items that composed the MM-RAP, 17 met the inclusion criteria of having a correlation of > or =0.40 on the primary factor analyses. The 3 items that assessed pain intensity met the inclusion criteria as well as the 2 items that assessed satisfaction. Two of the 3 items that assessed disability met the inclusion criteria; however, the missed school item did not. The sleep problem and the loss of appetite items in the nonpain items also did not meet the inclusion criteria in both components of the nonpain symptoms scale. However, the loss of appetite item met the inclusion criteria in the disability scale with a correlation of 0.6. The 2 items that did not meet the inclusion criteria (missed school days and sour taste) will be eliminated in the revised measure for RAP.

The MM-RAP demonstrated good reliability evidence in population samples. Children who have RAP and are seen at pediatric gastroenterology or primary care pediatric clinics have similar responses, showing that the measure performed well across several populations. Age did not affect the reliability of responses. The MM-RAP included 4 dimensions, each with several items that may identify disease-specific dimensions. In addition, dividing the nonpain symptoms scale into 2 components instead of 1 component could assist in creating a disease-specific measure. The present study focused exclusively on developing the multidimensional measure for RAP in children that could assist physicians in evaluating the efficacy of RAP treatment independent of psychological evaluations. In addition, the measure was designed for use in clinical trials that evaluate the efficacy of RAP treatment and to allow comparison between intervention studies. In conclusion, we were able to identify 4 dimensions of RAP in children (pain intensity, nonpain symptoms, pain disability, and satisfaction with health). We demonstrated that these dimensions can be measured in a reliable manner that is applicable to children who experience RAP in various settings.