TTG IgA in Functional Constipation : Is It Rational to Be Evaluated ?

Background: It is suggested that constipation could be due to celiac disease (CD); therefore, this study aimed to determine the prevalence of positive tissue transglutaminase (tTG) IgA test among children with functional constipation (FC). Methods: In this case-control study, 182 consecutive patients with FC who fulfilled the Rome III criteria as cases were compared with 240 healthy children as the control group in terms of suspicious CD by measuring the serum tTG IgA level. Results: There was a significant difference in favor of the case group in terms of serum tTG IgA levels (P = 0.000). The probability of having CD would change based on belonging to each group (case/control odds ratio [OR] = 0.222). Conclusion: With respect to these data, tTG IgA level was observed to be significantly higher in patients relative to healthy children; therefore, it is recommended that patients be screened for CD through the tTG IgA.


Background
Functional constipation (FC) is recognized as a frequent problem in children.2][3] The most common initiator of FC in childhood is an experience of painful defecation. 4he estimated prevalence of FC is between 0.3% to 8% of pediatric population that is different according to race and geographic regions. 2,4The FC is diagnosed based on Rom III criteria and there is no need for laboratory workup except for precise history and physical examination, [1][2][3][4][5] though some authors suggest evaluation for celiac disease (CD) in constipated patients especially in severe and refractory cases before making the diagnosis of FC in such patients. 5,6[10] Its symptoms and age of presentation have also changed. 9,10The important message of these alterations is that panorama of CD may change according to the community.Altered pattern of CD and observation of completely asymptomatic forms of disease reveal the fact that the typical CD represents just the tip of iceberg.][13] Today, clinicians use the tissue transglutaminase (tTG) IgA for determining CD as highly indicative of CD and according to population-based studies, its positivity is hand to hand with CD specific HLA genes and also correlates strongly with the intestinal mucosal damages. 8,9,14ith this insight that tTG IgA is trustable screening test and CD may potentially be presented with constipation, rather than other classic symptoms or growth retardation, this study was conducted to evaluate the tTG IgA level in the FC patients.

Methods
This single center case-control study was carried out from 2011 to 2013 on 182 patients aged less than 16 years old and with FC using Rome III criteria; they were referred to pediatric clinics of Zabol University of Medical Sciences.Moreover, 420 healthy children who had annual checkup were enrolled in the present study to be compared to the cases.All subjects were examined precisely and meticulous medical history was obtained.Subjects with preexisting history of CD, thyroid dysfunction, calcium abnormalities, inflammatory bowel disease, IgA deficiency, organic cause for constipation, those with gastrointestinal, endocrine, and metabolic diseases, iron deficiency, liver diseases, renal disorders, fever, or chronic conditions were excluded.Examination for perianal erythema, fresh rectal bleeding, and anal fissures was done.Rome III criteria in FC encompass the followings: 1-Neonates and toddlers At least two of the following symptoms must occur for at least one month: • ≤2 defecations per week • ≥1 episode per week of incontinence after the acquisition of toileting skills, • History of excessive stool retention • History of painful or hard bowel movements • Presence of a large fecal mass in the rectum, and • History of large-diameter stools that may obstruct the toilet 2-Children and adolescents Symptoms must occur at least once per week for at least two months and include two or more of the fol lowings in a child with a developmental age of >4 years with insufficient criteria of irritable bowel syndrome: • Two or fewer defections in the toilet per week • At least one episode of fecal incontinence per week • History of retentive posturing or excessive volitional stool retention • History of painful or hard bowel movements • Presence of a large fecal mass in the rectum • History of large diameter stools that may ob struct the toilet After night fasting (at least six hours), at 8:00 am, 5 mL blood was obtained from the study subjects and the serum was immediately separated by centrifuge and these serum samples were held in a -70°C fridge for tTG IgA measurements.For serologic evaluation of TTg IgA, 250 micron of the isolated serum of these samples was used, using commercial recombinant ELISA Kit with normal limit of 20 U/mL tTG IgA.

Statistical Analysis
Categorical and continuous variables were compared between cases and controls using chi-square and t tests, respectively.Logistic regression model was applied to estimate the association between potential risk factors and FC.

Results
The subjects were 602 children (mean age 5.1 years; 55.5% boys) who were divided into two case and control groups with 182 (30.2%) and 420 (69.8%) subjects, respectively.Mean age of boys and girls was 5.01 ± 0.171 and 5.23 ± 0.188 years, respectively.In the case group, there were approximately 29.9% males and 30.6% females.In the control group, there were 70.1% males and 69.4% females.Table 1 shows the results of independent t test for the comparison to the control and FC patients.The weights of the cases (17.9121 ± 9.078) and controls (21.039 ± 7.871) were significantly different (P < 0.001).Mean of tTG was significantly higher in the case (13.307 ± 21.990) group compared to the controls (6.9405 ± 6.685) (t=5.385;P < 0.001).Age of participants in two groups of case and control did not show any difference (P = 0.564).Similar factors were  1 shows the results.Weight, tTG level, and age were the same in two genders.Table 2 shows sex status in tTG IgA levels according to the cut-off point of 20 for negative and positive states.In negative state of tTG (<20), 91.791% were females when this percentage for males was 91.317%.There was no relationship between the levels of TTg IgA and sex (r = 043, P = 0.884).The confidence interval for odds ratio (0.527, 1.678) for sex factor revealed that gender plays the role of both risk and protection.Both sex groups had approximately the same chance to have lower tTG IgA level (odds ration [OR] = 0.941 ); it shows that sex had no effect on tTG IgA level.However, for groups viz case and control, the 95% CI =0.122, 0.404 displayed that being a member of case group would affect the probability of having less than 20 in tTG IgA (OR = 0.222) and it means that the control group had a preservative effect, because a low percentage of the subjects in the case group had a level of tTG IgA less than the cut-off point (20).

Discussion
The results of this study revealed no significant difference between two groups in terms of age and sex, although the weight had a considerable disparity.Similarly, in the studies performed by Dehghani et al 4 , there was the systemic review of van den Berg et al, which demonstrated no considerable differences between the genders. 5triking disparity in the weight between two groups could have resulted either from the anorexia in the domain of FC that varies from 10% to 38% in these patients, or from silent undiagnosed CD. 8 While the CD-presenting symptoms in the childhood include the classic malabsorption syndrome, there are a number of caveats that need to be recognized in the pediatric population. 7,9,10First is the fact that children with newly presenting CD may not have classical symptoms and signs.It has been proposed that atypical features are mostly found in children.Second is that CD might have a monosymptomatic manifestation such as constipation, and finally the CD patients may be completely asymp-tomatic and even obese. 9,10n a study on 215 patients with CD, Murray et al reported that constipation had a prevalence of 39% (83 cases) at the presentation and before initiating gluten-free diet. 15n the present study, mean tTG IgA levels and serological positive subjects for CD (tTG IgA ≥20) evidenced a statistical striked favour for FC patients.Pelleboer et al performed a cohort study to evaluate the prevalence of CD, hypothyroidism, and hypercalcemia on 370 consecutive children with constipation.Their results showed that CD was significantly higher in patients with constipation; they suggested screening for CD in such patients. 16n contrast, Chogle et al according to a retrospective cohort survey that was conducted on 7472 children with a mean age of 7.9 years during 2007 to 2011 concluded that constipation alone did not increase the possibility of CD; therefore, screening for CD was not cost-beneficial. 12cNicholl and Egan-Mitchell suggested that a reasonable influencing clinical picture in CD by the factors such as anorexia and the extent of the mucosal damage and constipated stools has more likelihood when the anorexia is prominent. 17ome guidelines suggest that patients with functional gastrointestinal disorders (FGIDs) should be screened by the serologic testing for CD; however, it is open to debate that whether CD is more frequent in populations with FGIDs or not. 11ristofori et al reported higher prevalence of CD among children with IBS than among general pediatric population. 18n a systematic review and meta-analysis performed by Ford et al, authors found a fourfold prevalence of biopsy-proven CD in the cases with IBS; this study that involved 14 surveys encompassed 2278 patients that had diagnostic criteria for IBS. 19n another meta-analysis on 15 studies, Ford documented that biopsy-proven CD is more prevalent among patients with dyspepsia than among controls. 20

Limitations
The limitations of the present study included the single center study and lack of endoscopy and biopsy for positive patients.

Conclusion
Based on the present study, it seems that the patients with FC should be screened for CD by tTG IgA; however, following endoscopic mucosal confirmation is suggested in the serologic CD positive patients.

Ethical Approval
The parents' informed consent was obtained.

Table 1 .
Independent T Test for Demographic Factors in Groups of Control and Patients With Constipation

Table 2 .
Distribution of tTG IgA According to the Cut-off Point of 20 for Sex and Groups