Abstract
Background/aims
Food antigens are thought to play a vital role in the initiation and perpetuation of Crohn’s disease (CD). The main purpose of this study was to evaluate the potential association of serum food specific IgG antibodies and small bowel (SB) inflammation in CD patients.
Methods
We conducted a prospective observational study with 96 CD patients. Demographic, disease-related data and inflammatory parameters were collected. Serum food IgG antibodies were measured using enzyme-linked immunosorbent assay (ELISA). Capsule endoscopy was performed to detect SB inflammation quantified by the Lewis Score.
Results
Seventy-eight of (81.3%) CD patients were detected positive for at least one food-specific antibody. The five most prevalent food antibodies in CD patients were tomato, egg, corn, rice, and soybean. Patients with SB inflammation had a higher positive rate of food IgG antibodies (P = 0.010) and more IgG-positive food items (P = 0.010) than those without. Specifically, patients with SB inflammation were more likely to have positive food-specific IgG against egg (P = 0.014), corn (P = 0.014), and wheat (P = 0.048). Additionally, the number of positive food IgGs ≥ 3 and elevated ESR were independently associated with concurrent SB inflammation (P = 0.015 and P = 0.013, respectively).
Conclusion
Our study confirmed that CD patients with SB inflammation had a higher positive rate of food IgG antibodies and more IgG-positive food items. The number of food positive IgGs ≥ 3 and elevated ESR were independently associated with concurrent SB inflammation.
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Abstract
Background/aims
Food antigens are thought to play a vital role in the initiation and perpetuation of Crohn’s disease (CD). The main purpose of this study was to evaluate the potential association of serum food specific IgG antibodies and small bowel (SB) inflammation in CD patients.
Methods
We conducted a prospective observational study with 96 CD patients. Demographic, disease-related data and inflammatory parameters were collected. Serum food IgG antibodies were measured using enzyme-linked immunosorbent assay (ELISA). Capsule endoscopy was performed to detect SB inflammation quantified by the Lewis Score.
Results
Seventy-eight of (81.3%) CD patients were detected positive for at least one food-specific antibody. The five most prevalent food antibodies in CD patients were tomato, egg, corn, rice, and soybean. Patients with SB inflammation had a higher positive rate of food IgG antibodies (P = 0.010) and more IgG-positive food items (P = 0.010) than those without. Specifically, patients with SB inflammation were more likely to have positive food-specific IgG against egg (P = 0.014), corn (P = 0.014), and wheat (P = 0.048). Additionally, the number of positive food IgGs ≥ 3 and elevated ESR were independently associated with concurrent SB inflammation (P = 0.015 and P = 0.013, respectively).
Conclusion
Our study confirmed that CD patients with SB inflammation had a higher positive rate of food IgG antibodies and more IgG-positive food items. The number of food positive IgGs ≥ 3 and elevated ESR were independently associated with concurrent SB inflammation.
ArticleOpen access18 January 2021
Introduction
Crohn’s disease (CD) is a chronic, progressive and relapsing inflammatory disease characterized by transmural inflammation involving any part of the entire gastrointestinal tract. Relapsing bowel inflammation will accumulate structural bowel damage, which increases the risk of developing severe complications necessitating surgical intervention. Furthermore, small bowel (SB) involvement is associated with a poor prognosis and a higher likelihood of suffering complications [1, 2].Therefore, it is very important to closely monitor disease activity and achieve clinical persistent remission and mucosal healing to avoid the progression of bowel damage [3].
As to endoscopic assessment, ileocolonoscopy with biopsy is considered the first-line procedure to evaluate intestinal lesions among patients with CD. However, disease may be confined only to the SB in one-third of patients [4]. It is more challenging to evaluate the small bowel disease because ileocolonoscopy cannot reach the involved upper or medium bowel segment. Small bowel capsule endoscopy (SBCE) was introduced in 2000 to provide a reliable method to visualize directly the entire small bowel [5]. SBCE is considered a useful tool for the evaluation of suspected and established CD. SBCE has been shown to be more sensitive in detecting lesions in the proximal small bowel than magnetic resonance imaging enterography (MRE) and computed tomography enterography (CTE), with comparable accuracy for distal lesions [6,7,8]. It has been reported that SBCE is also useful for treatment guidance in patients with established CD [9]. Recently, a recent prospective cohort study also found that SBCE could predict both short-term and long-term risk of CD flare during follow-up [10]. Although noninvasive and generally well tolerated, SBCE is time consuming and costly to perform and entails the small but significant risk of capsule retention [11, 12].
A noninvasive inflammatory biomarker with good accuracy for diagnosing and monitoring CD is crucial in clinical practice. C-reactive protein (CRP) and Fecal calprotectin (FCP) are the most commonly used inflammatory biomarkers in clinical practice. However, the accuracy of CRP to predict intestinal inflammation was modest [13]. CRP can underestimate SB inflammation detected by SBCE in quiescent CD [14, 15], limiting its clinical utility for disease surveillance. FCP has a high accuracy in the evaluation of colonic inflammation, so it can be used as a reliable marker to predict disease relapse and guide treatment. However, accumulating evidence suggests that FCP shows a weak correlation with SBCE findings, limiting its utility in the prediction of SB inflammation [16,17,18].
Several studies have found that CD patients have a higher prevalence and titer of serum food-specific IgG antibodies than ulcerative colitis (UC) patients and healthy individuals [19,20,21]. Patients with SB involvement may be more likely to develop food-specific IgG antibodies than patients without small bowel involvement [20]. A possible explanation is that intestinal barrier dysfunction allows food antigens to enter the submucosa and contact with immune cells directly, leading to the production of food antibodies. Therefore, food-specific antibodies may serve as a potential marker for predicting SB inflammation. The purpose of this study was to investigate the prevalence of food specific IgG antibodies in CD patients. We also sought to confirm the association between food-specific IgG antibodies and SB disease activity evaluated by SBCE.
Material and methods
The study population
From April 2017 to April 2019, CD patients with known SB involvement were prospectively recruited for this study. This study was conducted at the First Affiliated Hospital of Fujian Medical University, a tertiary care center for the management of CD in Fujian Province, China. The diagnosis of CD was established based on a combination of clinical, endoscopic, radiological, and histological criteria [22]. All patients signed an informed consent, and the study protocol was approved by the Ethics Committee of the First Affiliated Hospital of Fujian Medical University, China, in accordance with the Declaration of Helsinki.
The inclusion criteria included: a previous diagnosis of CD with SB involvement; age older than 14 years; and willingness to undergo CTE or MRE at enrollment. The exclusion criteria were: inability to understand or unwillingness to provide informed consent; serious liver, kidney, brain or cardio-respiratory comorbidities; difficulty in swallowing, history of dysphagia or aspirations; use of non-steroidal anti-inflammatory drugs within the previous month; definite intestinal stricture identified by imaging or bowel obstruction at enrollment.
Sample size estimation
A non-probability convenience sampling method was used to recruit CD patients. The sample size was calculated using PASS version 11.0 (NCSS Statistical Software, Kaysville, UT, United States). According to previous reports [19,20,21], the estimated positive rate of food-specific antibodies in CD patients is approximately 80%. The sample size obtained was 96 at a margin of error of 5% and a confidence level of 95%.
Data collection
The disease activity in CD patients was scored by the CD activity index score (CDAI) [23]. Demographic data, body mass index (BMI), smoking status, history of intestinal surgery, disease duration, disease location and behavior were collected for each patient at the time of enrollment. Information about medical treatment was also collected.
At enrollment, peripheral blood was collected from each patient for analysis of total white blood cell count, eosinophil ratio, hemoglobin, platelet count, and inflammatory markers, such as CRP and erythrocyte sedimentation rate (ESR). A stool sample was also collected to determine FCP using a commercially available colloidal gold immunofiltration assay (Wizbiotech, Xiamen, China).
Serum food-specific IgG antibodies test
A commercially available enzyme-linked immunosorbent assay (ELISA) kit (HOB Biotech Group Corp., Suzhou, China) was used to quantitatively determin serum IgG antibodies against 14 common food-derived antigens, including beef, codfish, chicken, corn, egg, crab, mushroom, milk, rice, pork, shrimp, soybean, wheat and tomato. The whole detection process was carried out in accordance with the manufacturer’s instructions, and the final results were obtained by the ELISA plate reader (Infinite F50, TECAN, Männedorf, Switzerland) at an absorbance of 450 nm.
A food IgG concentration less than 50 U/mL was considered negative (Grand 0). Levels of 50–100 U/mL, 100–200 U/mL, and greater than 200 U/mL were classified as mild sensitivity (Grade 1+), moderate sensitivity (Grade 2+) and high sensitivity (Grade 3+), respectively.
Capsule endoscopy examinations
MRE or CTE were performed in all patients before CE examination to detect severe intestinal stricture and avoid capsule retention. On the day before examination, patients underwent bowel preparation with 2-L of 6.8% polyethylene glycol electrolyte oral solution (Shutaiqing, Staidson Beijing Biopharmaceuticals Co., Ltd., Beijing, China). After a 12-h overnight fast, patients swallowed the capsule (Jinshan Science & Technology Co., Ltd., Chongqing, China). After 8–10 h of recording, the images were downloaded to the OMOM capsule endoscopy workstation (Jinshan Science & Technology Co., Ltd., Chongqing, China).
All images were reviewed carefully by two experienced gastroenterologists blinded to the study design and clinical data of the patients. SB inflammation was quantified using the Lewis score (LS) [24]. LS is considered as SB mucosal healing or no clinical significant inflammation if lower than 135 points, mild inflammation 135–790 points, and severe inflammation 790 points [24].
Statistical analysis
Data were analyzed using SPSS software version 22.0 (IBM, Armonk, New York, USA). Continuous variables with normal distribution were presented as mean ± standard deviation (SD) and continuous variables with non-normal distribution were presented as median ± interquartile range. Either the Student’s t test or the Mann–Whitney U-test was used for comparisons between two groups in term of continuous variables. Variance was compared with the F-test. Categorical data were presented as counts, and assessed using Fisher’s exact test or the χ2 test. Univariate and multivariate logistic regression analysis were used to identify the association between SB inflammation and clinical characteristics and food IgGs. A P value < 0.05 was considered statistically significant.
Results
Clinical and demographic characteristics of the included patients
A total of 96 patients with CD were finally included in this study. The baseline clinical and demographic characteristics of the included patients are shown in Table 1. The median age of patients was 25 (18, 31) years and 63 (66%) were men. The median disease duration from the time of disease onset to study enrollment was 24 (10, 48) months. 21/96 (21.9%) were in the active stage (CDAI ≥ 150) at entry. Thirty-seven (38.5%) had elevated CRP (>10 mg/dL), and twenty-one (21.9%) had elevated FCP (>100 µg/g). SBCE examinations demonstrated SB inflammation in 71(74%) patients (LS ≥ 135).Table 1 Baseline characteristics of the included Crohn’s disease patients.
Serum food-specific IgG antibodies
The levels of serum food-specific IgG antibodies of CD patients against fourteen common food antigens are shown in Table 2. In this study, at least one food antibody was detected positive in 78 (81.3%) patients with CD, and among them 15.6% (15/96), 15.6% (15/96), and 50.0% (48/96) of patients had one, two and more than two types of food antibodies respectively. The mean number of food antibodies was 3.0 ± 2.5. The five most prevalent food antibodies in CD patients were tomato (58/96, 60.4%), egg (51/96, 53.1%), corn (51/96, 53.1%), rice (43/96, 44.8%), and soybean (23/96, 24.0%).Table 2 Distribution of positive food IgG antibodies in Crohn’s disease patients.
Comparison of clinical characteristics between patients with and without small bowel inflammation
As shown in Table 3, there was no statistically significant difference between CD patients with and without SB inflammation with respect to age, gender, BMI, disease location, disease duration, allergic disease history, current treatment with 5-amino salicylic acids (5-ASAs), steroids or immunosuppressants. Moreover, statistical analysis failed to show any significant difference between patients with and without SB inflammation in terms of the median CDAI (49.0 vs. 66.2, respectively; P = 0.233) and serum CRP levels (4.18 vs.8.39, respectively; P = 0.133). Among patients with SB inflammation, 17 (23.9%) had a CDAI ≥ 150, and 30 (42.3%) had an elevated CRP level. By contrast, 4 (16.0%) patients without SB inflammation had a CDAI ≥ 150 and 7 (28.0%) had an elevated CRP level (P > 0.05 for both comparisons). Conversely, patients with SB inflammation tended to have a higher incidence rate of perianal involvement (70.4 vs 48.0%, P = 0.044) and higher inflammatory activity with an ESR > 20 mm/h (69.0 vs 36.0%, P = 0.004), compared to patients without SB inflammation.Table 3 Demographic and Clinical characteristics in Crohn’s disease patients according to the presence of small bowel inflammation.
Comparison of food-specific IgG antibodies in sera of patients with and without small bowel inflammation
As shown in Table 4, CD patients with SB inflammation showed a higher positive rate of food IgG than those without (87.3vs 64.0%, P = 0.010). The mean number of food positive IgG items in patients with SB inflammation was higher than patients without SB inflammation (3.4 vs 1.9, P = 0.010). Patients with SB inflammation were more likely to develop more than two different food IgGs than patients without SB inflammation (57.7 vs 28.0%, P = 0.011). Specifically, patients with SB inflammation were prone to have a higher positive rate of food specific IgG against egg (60.6 vs 32.0%, P = 0.014), corn (60.6vs 32.0%, P = 0.014), and wheat (21.1 vs 4.0%, P = 0.048), compared to those without SB inflammation. Furthermore, patients with SB inflammation were more likely to have positive food IgG against rice with a marginally significance than those without SB inflammation (50.7 vs 28.0%, P = 0.050). No significant difference in food IgGs against chicken (P = 0.173), crab (P = 0.260), shrimp (P = 0.435), codfish (P = 0.467), pork (P = 0.396), milk (P = 0.165), soybean (P = 0.278), tomato (P = 0.140), or mushroom (P = 0.752) were observed between patients with and without SB inflammation. Figure 1 shows the distribution of positive food antibodies in CD patients with and without SB inflammation.Table 4 Comparison of serum food-specific IgG antibodies positivity between patients with and without small bowel inflammation.
Association between small bowel inflammation and clinical characteristics and food IgGs antibodies in CD patients
As shown in Table 5, univariate logistic regression analysis indicated that SB inflammation was significantly associated with age, perianal involvement, biologicals treatment, elevated ESR and number of positive food IgGs ≥ 3. Multivariate analysis revealed that biologicals treatment (odds ratio [OR] = 3.945, 95% confidence interval [CI] 1.333–11.680, P = 0.013), elevated ESR (OR = 3.587, 95% CI, 1.278–10.068, P = 0.015) and number of positive food IgGs ≥ 3 (OR = 3.814, 95% CI 1.284–11.333, P = 0.016) remained significantly and independently associated with SB inflammation.Table 5 Results of univariate and multivariate analyses examining factors associated with small bowel inflammation in Crohn’s disease patients.
Discussion
Our prospective study shows that food-specific IgG antibodies are highly prevalent in CD patients. The five most prevalent food antibodies in CD patients are tomato, egg, corn, rice, and soybean. Interestingly, serum food IgG antibodies were found to be associated with concurrent SB inflammation evaluated by SBCE. Patients with SB inflammation had a higher positive rate of food IgG antibodies and more IgG-positive food items. Additionally, equal or more than three IgG-positive food items and elevated ESR were independent predictors of SB inflammation.
Most (81.3%) of CD patients were detected positive for at least one food specific antibody, which is consistent with previous studies [19,20,21]. This result is not surprising because increased intestinal permeability is a typical feature of CD patients, which facilitates food antigens into the circulation and then stimulates the production of relevant antibodies. More than two different food specific antibodies were detected positive in half of the patients in present study. The five most prevalent food antibodies in CD patients were tomato (60.4%), egg (53.1%), corn (53.1%), rice (44.8%), and soybean (24.0%), similar to a previous study [21]. Wang and colleagues [25] recently reported that CD patients exhibited more intense immune response to food antigens than UC and controls, and the number of food IgG-positive items could be used to discriminate CD from UC and healthy controls, with high diagnostic value.
Previous studies have shown that CD patients with SB involvement are significantly associated with lactose maldigestion [26, 27]. Notwithstanding, ref. [20] reported that patients with only small intestine involved were prone to have a higher positive rate of food antibodies (82.5%) with an unremarkable statistical difference. When patients were regrouped, those with small bowel involved had a significantly higher positive rate than those without (79.7 vs. 60.5%, p = 0.005). However, no significant correlation was found between positive rates of food-specific IgG and disease location in CD patients in the studies by ref. [19] and ref. [21]. This may be due to the fact that disease location determined according to the Montreal classification cannot distinguish active small bowel mucosal inflammation. LS based on CE findings may be more precise for reflecting the real state of small bowel. In our study, we used LS to identify whether patients had active SB inflammation. Higher positive rates of food IgG antibodies and more IgG-positive food items were found in patients with SB inflammation (LS ≥ 135) in the present study. It is not surprising that intestinal stenosis, food indigestion and increased intestinal mucosa permeability are commonly presented in patients with small intestinal CD, which might allow more chances for food antigens to be recognized by the immune system and produce specific antibodies. The types of food IgG antibodies may differ owing to the diversity of diet habits in different regions, while the number of food-positive antibodies may be more precise to reflect the current bowel state. In this study, we found that patients with active SB disease had a higher positive rate of food antibodies, and more food-positive items. The number of food-positive items (≥3 positive) was an independent predictor of SB inflammation. This finding may provide a noninvasive method for diagnosing and monitoring CD in clinical practice.
Our study also has several main drawbacks. Firstly, it was a single center, cross-sectional analysis that included a relatively small number patients. Secondly, this research was not a follow-up study to investigate whether improvement of SB disease severity could be paralleled by a reduction in the positive rate of food-specific IgG after medical treatment. Thirdly, children with CD were excluded in our study. Additionally, the study did not investigate the patient’s dietary habits, which may have an impact on the types and titers of food IgG.
In conclusion, our study confirms that serum food-specific IgG antibodies are highly prevalent in CD patients. Notably, CD patients with SB inflammation have a higher positive rate of food IgG antibodies and more IgG-positive food items. The number of food-positive IgGs (≥3) is independently associated with concurrent SB inflammation. This finding may provide a convenient and noninvasive method for predicting SB inflammation in clinical practice.
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