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The inflammatory bowel diseases are chronic inflammation of the digestive tract. Serum Beta 2 microglobulin levels increase in all chronic inflammatory disease. This increase is linked to the severity and extant of inflammation. In the study we examined Beta 2 microglobulin serum levels in patients suffering from inflammatory bowel diseases, to assess the extent of the disease and the possible correlation between these serum levels and the activity of inflammatory bowel diseases.
Methods: Overall, 78 inflammatory bowel diseases patients and 30 healthy controls were enrolled. We examined Beta 2 microglobulin serum levels in 43 ulcerative colitis patients, 35 with Crohn's disease and 30 control subjects, using an enzymatic method. Ulcerative colitis and Crohn's disease patients were divided into two groups according to disease activity: Active and remission. Subjects were divided into two groups according to extend of disease: Left and pancolitis for ulcerative colitis; °leitis and ileocolitis for Crohn's disease. All groups were compared for the mean serum Beta 2 microglobulin levels
Results: Mean Beta 2 microglobulin values were significantly higher in ulcerative colitis and Crohn's disease patients than in healthy controls. Mean Beta 2 microglobulin values were significantly higher in inflammatory bowel diseases activity than remission. The difference between groups (ulcerative colitis and Crohn's disease) in terms of serum Beta 2 microglobulin levels was statistically insignificant.
Conclusion: Serum Beta 2 microglobulin levels could be used is an activity parameter in inflammatory bowel diseases.
Key words: Ulcerative Colitis, Crohn Disease, Beta 2 Microglobulin
The Inflammatory bowel diseases (IBD), consisting of ulcerative colitis(UC), Crohn's disease (CD) and indeterminate colitis which are recognized by idiopathic and chronic inflammation of the digestive tract. Disease activity in IBD is defined using both direct as well as noninvasive laboratuary markers, as endoscopic examination, which is essential for diagnosis and determining disease activity, is invasive and expensive (1,2). Laboratuary markers such as C reaktive protein(CRP), erythrocyte sedimentation rate(ESR), white blood count(WBC) and platelet count, albumin, fecal calprotectin and acid glycoprotein(orosomucoid) have been investigated in IBD for different aims- diagnosis, differential diagnosis, disease activity, response to therapy, and estimate of relapse (3-6) . An ideal marker should be easy and rapid to perform and cheap for patients and laboratuaries. It should be disease spesific,and should be able to determine disease activity, follow the effect of treatment; and at last it should have a prognostic merit againts relapse or recurrence of the disease (7). Nevertheless, optimal marker has not yet been proven to possess all the conditions.
Beta 2 microglobulin(B2-M) is a low molecular weight protein and is released by activated T and B lymphocytes on activation. Plasma concentrations vary from 1-3 µg/mL. The estimated half life time is two hours. It is filtered through the glomeruli and levels increase age due to reducing kidney function (8). In this respect B2-M has been shown to increase in several inflammatory and hematologic disorder, such as systemic lupus erythematosus, acquired immunodeficiency syndrome (AIDS), multiple myeloma, lymphoma, leukemia (10-12). Serum B2-M levels increase is associated to the severity and extant of inflammation. The aim of present study was to evaluate value of B2-M levels to determine UC and CD. In this way we examine correlation between B2-M levels and disease clinical and endoscopic activity. A few studies have investigated B2-M in identifying individuals at activity for IBD (13-16).
MATERIALS AND METHODS
A total of 108 subjects were included in the study. Seventy-eight patients were suffering from IBD; 43 of them from UC and 35 of them from CD. The diagnosis of IBD was based on standard clinical, radiological, endoscopic and histological criteria. Inclusion criteria for IBD patients were normal renal function and absence of any other disease that could influence the serum levels of B2-M.
Complete blood count, ESR, CRP, albumin were determined for both patients and controls. All IBD patients underwent colonoscopy at study entry. UC and CD patients were divided into two groups according to disease activity: Active and remission. Patients were divided into two groups according to extend of disease: Left and extensive for UC ; °leitis and ileocolitis for CD (table 1). On the initial examination, only two patients was classed as having proctitis and this patients was included in the left-sided group to compare inflammation parameters between two groups in active disease. All groups were compared for the mean serum β2M levels.
The extent of the UC was classified according to the Montreal classification (17). If involvement up to the splenic flexure was defined as left sided colitis; and involvement extends proximal to the splenic flexura was defined as extensive UC. Clinical disease activity was evaluated using a modified Truelove-Witts severity index(MTWSI). Clinical activite disease was defined as an estimated MTWSI score of 4 or higher and patients with a lower score than 4 were considered in to be remission(inactive) (18).The disease activities of CD patients were classified according to Harvey-Bradshaw index(HBI) (19).
Beta 2 microgloulin Assay
In the ADVIA 2400 Chemistry B2-M assay, a sample is diluted and reacted with a buffer that contains latex particles coated with antibody specific for B2-M. The formation of the antibody-antigen complex during the reaction results in an increase in turbidity, the extent of which is measured as the amount of light adsorbed at 545nm. The B2-M concentration in a sample is determined by constructing a standard curve from the absorbance of a reagent blank and a single-level calibrator. Blood samples were collected from a peripheral vein after an overnight and were subjected to centrifugation with the speed of 3000 rounds per minute for 10 min, at 4°C to obtain serum. All blood samples were stored at -20°C immediately after separation from peripheral blood prior to analysis.
Data analysis was performed using Statistical Package for Social Sciences(SPSS) version 13 software (SPSS Inc., Chicago,IL,United States). Values were presented as mean ± Standard deviations. Continuous variables were analyzed using unpaired Student t test or 1-way analysis of variance (ANOVA). Chi-square analysis was used for categorical variables. Pearson correlation coefficient was utilized to see the correlation between B2-M and other markers. The sensitivity and specificity of B2-M, CRP, ESR, WBC levels for the detection of patients were calculated under various cut-off ranges, and the receiver operating characteristic (ROC) curves were drawn. A 'p' value of less than 0.05 was considered statistically significant.
The demographic and clinical characteristics of patients and control subjects were summarized in table 1. There were no statistically significant differences between the age, gender of the study participants. The mean serum B2-M levels in the control group, UC and CD were 1.71, 2.41 and 2.24 respectively. Table 1 shows serum B2-M and the other laboratory values of study participants onset of the study. Mean B2-M and ESR values were significantly higher in ulcerative colitis and Crohn's disease patients than in healthy controls. The difference between groups (ulcerative colitis and Crohn's disease) in terms of serum B2-M, ESR and albumin levels was statistically insignificant. Mean albumin values were significantly lower in UC and CD patients than controls. Mean CRP and WBC levels were statisticallay insignificant between patients and controls(table 1). No correlation was found between B2-M and other inflammation markers for UC patients.( CRP: r = 0.281, p =0.079, ESR: r = 0.14, p = 0.383 , WBC: r = 0.222, p = 0.162).While correlation was found between B2-M and CRP, ESR for CD patients(CRP: r = 0.79, p =0.001, ESR: r = 0.76, p = 0.001).
B2-M values ≥ 1,96 mg/L had 62% sensitivity, 76% specificity, 79% positive predictive value (PPV), and% negative predictive value (NPV) for UC patients. ROC curve analysis suggested that the optimum B2-M cut off point for active UC was 2.02 mg/L, with a sensitivity, specificity, PPV and NPV of 79%, 78%, 88%, and 64% respectively( figure 1). Same analyses for other inflammation markers were summarized in table 2. Serum B2-M and CRP levels of the active UC patients were significantly higher than those of inactive patients.p<0.005
B2-M values ≥ 1,70 mg/L had 80% sensitivity, 53% specificity, 66% positive predictive value (PPV), and 69% negative predictive value (NPV) for CD patients. Serum B2-M, CRP and ESR levels of the active CD patients were significantly higher than those of inactive patients. ROC curve analysis suggested that the optimum B2-M cut off point for active CD was 1,84 mg/L, with a sensitivity, specificity, PPV and NPV of 78%, 75%, 85%, and 63% respectively.
IBD contains various different conditions, with the main two types being CD and UC. Both circumstances are characterized by chronic inflammation of the gut tract.They are often considered together given their similar aetiology and symptoms. The clinical courses are marked by exacerbations and remissions, which may develop spontaneously or in response to medical treatment (20,21). The determination of inflammatory activity has a significant role for the assessment of disease severity and for the therapeuthic management. Disease flares consist in a indiscriminate way and are often unpredictable. Inflammatory markers have been investigated in IBD for diagnosis, disease activity and prediction of relapse. Some authors proved a good correlation B2-M and disease activity. Nevertheless results were conflicting and not all authors were able to confirm these findings (13-16).
In the present study, we demonstrated that with active IBD have elevated B2-M concentrations in comparison with inactive patients and healthy controls. Serum B2-M activity is found to have high sensitivity, specificity and predictive values in active IBD patients. High levels of B2-M activity in the sera of active IBD patients, compared to inactive IBD and controls, support the view that activated macrophages and T-lymphocytes may have a role in the cytokine network of the inflammatory cascade of IBD with in the disease pathophysiology.