Serum lipopolysaccharide-binding protein and soluble CD14 are markers of disease activity in patients with Crohn's disease

Inflammatory bowel disease (IBD) is a multifactorial condition with both environmental and genetic components, displaying heterogeneity in terms of disease presentation as well as response to treatment.¹ Many aspects of its two forms, Crohn's disease (CD) and ulcerative colitis (UC), still present challenges for physicians: diagnosis, prognosis, assessment of disease activity and severity, treatment, as well as the outcome of therapy. For each of these aspects there is no single gold standard test or examination. Instead, physicians have to rely on a complex evaluation of symptoms, physical examination, laboratory indices, imaging techniques, and endoscopy with histology to make the diagnosis, to assess severity, and to predict the outcome of the disease.

IBD follows an alternating disease course and both CD and UC are characterized by periods of remission and relapses. However, disease flare-ups occur in a random way and are often unpredictable. Based on the half-life and changes over time, serum laboratory and fecal markers may be the best modality for monitoring disease activity as well as predicting short- (6-week) or medium-term (6–12-month) relapses. C-reactive protein (CRP) is a marker of inflammation and is often used as an indicator of disease activity in CD.², ³ Only a few clinical studies have assessed the value of CRP alone or in combination with other inflammatory serum markers in the disease course and predicting clinical response or remission in CD patients. In an early study by Brignola et al,⁴ CRP was not among the panel of best markers, which could have distinguished relapsers from nonrelapsers. Two prospective studies found CRP alone⁵ or in a combination with erythrocyte sedimentation rate (ESR)⁶ useful for predicting short-term relapse. Moreover, a recent population-based study by the IBSEN group has demonstrated⁷ that CRP at diagnosis or during follow-up was able to predict medium-term outcome as assessed by the need for resective surgery.

The exact mechanisms leading to CRP elevation in CD are not fully understood. The accumulation of mesenteric fat, which is a major site of interleukin (IL)-6 and tumor necrosis factor-alpha (TNF-α) synthesis, has been proposed to contribute to CRP production in CD. Another potential explanation could be that during disease flare-up, even with a lack of overt infection, a significant bacterial translocation occurs due to the transmural inflammation of the gut wall.⁶ Bacteremia is one of the strongest stimulators of CRP production.⁸ The role of more specific laboratory markers of bacteremia, however, was rarely assessed. Lipopolysaccharide-binding protein (LBP) plays key roles in promoting innate immunity against Gram-negative bacteria by transferring lipopolysaccharide (LPS) to a binding site of membrane-bound (m)CD14, which represents one part of the cellular LPS-signaling receptor complex (MD-2/Toll-like receptor 4 [TLR4]).⁹ In addition, LBP transfers LPS to soluble (s)CD14, resulting in activation of mCD14-negative cells such as endothelial and epithelial cells.¹⁰ Along with augmentation of the innate immune response to several bacteria and bacterial surface components, LBP and sCD14 seem to have a more complex immunomodulatory capacity at higher concentrations.¹¹ Similar to CRP, LBP is also an early acute-phase protein induced by IL-1, IL-6, and TNF-α.¹² In clinical studies, increased serum LBP concentrations were correlated with the onset of bacteremia¹³ and were a specific and sensitive marker in the differentiation between systemic inflammatory response syndrome (SIRS) and bacterial infection.¹⁴

In IBD, an association between an SNP in the promoter region of the CD14 gene (c.-159C>T, also known as CD14 c.-260C>T), which results in enhanced transcriptional activity and leads to significantly higher CD14 serum levels, has been described as a risk allele in several,^15,–17 but not all studies,¹⁸ either alone or through interaction with polymorphisms in the NOD2 (nucleotide oligomerization domain)/CARD15 (caspase activation recruitment domain) gene. In contrast, an association between LBP, sCD14, and other genetic markers of bacterial recognition (e.g., TLR4) or antimicrobial serology profile characteristic for CD patients (e.g., anti-Saccharomyces cerevisiae antibodies [ASCA] and antibody to bacterial outer membrane proteins [OMP]) with a more aggressive disease phenotype¹⁹ were not tested.

Furthermore, CD14 was a potent modifier of the severity of inflammation in animal models (IL-10-deficient and CD14-deficient mice) and confirmed the protective effect of CD14 against experimental IBD.²⁰ A Spanish study assessed the changes in LBP and sCD14 levels in adult patients with IBD.²¹ Increased serum levels of endotoxin, LBP, and sCD14 were shown in patients with a flare-up and decreased following treatment. An association between LBP and clinical disease activity indices was also reported. The accuracy of the markers in identifying active disease or predicting an upcoming flare-up, however, was not assessed. In a very recent cross-sectional study by Pasternak et al,²² LBP and endotoxin core IgA (EndoCAb) antibody but not sCD14 were found to be associated with disease activity in a pediatric CD population.

In the present study our aim was to investigate the association between serum LBP and sCD14 and clinical disease activity, the high-sensitivity C-reactive protein (hs-CRP),²³ and clinical phenotype in a large cohort of Hungarian CD patients. We also assessed the predictive value of these markers for disease flare-up. In addition, due to their shared role in bacterial recognition, we also investigated the associations between LBP, sCD14, and NOD2/CARD15 status as well as the antimicrobial serology profile.

Patients and Methods

Study Population

In all, 214 well-characterized, unrelated, consecutive CD patients (age: 35.6 ± 13.1 years old, male/female: 95/119, duration: 8.3 ± 7.5 years) were investigated. Their clinical data are presented in Table 1.

The diagnosis was based on the Lennard–Jones Criteria.²⁴ Age, age at onset, presence of extraintestinal manifestations (EIM; arthritis: peripheral and axial; ocular manifestations: conjunctivitis, uveitis, iridocyclitis; skin lesions: erythema nodosum, pyoderma gangrenosum; and hepatic manifestations: primary sclerosing cholangitis [PSC]), frequency of flare-ups (frequent flare-up: >1 clinical relapse/year²⁵), therapeutic effectiveness (e.g., steroid and/or immunosuppressive use at any time, steroid resistance²⁵: 19.8%), need for surgery (resections), the presence of familial IBD, smoking habits, and perianal involvement were investigated through a review of the medical charts by the physician and completing a questionnaire. Disease activity at the time of the blood sampling and during follow-up visits was calculated according to the Crohn's Disease Activity Index (CDAI).²⁶ The disease phenotype (age at onset, duration, location, and behavior) was determined according to the Montreal Classification.²⁷ Of the 149 patients in medically induced remission, 91 were eligible for the follow-up study. Clinical data and blood samples were prospectively captured. The follow-up period lasted 12 months in those patients showing no relapse, or until the date of flare-up in patients with clinical relapse (CDAI >150, ΔCDAI >100, and change in medical therapy). All relapses were of sufficient severity to warrant a change in treatment.

The control group consisted of 110 age- and gender-matched healthy blood donors (male/female: 48/62, age: 36.8 ± 12.6 years old). The control subjects did not have any gastrointestinal and/or liver disease and were selected from consecutive blood donors in Debrecen and Budapest. The study protocol was approved by the Ethical and Science Committee of the University of Debrecen and the Semmelweis University Regional and Institutional Committee of Science and Research Ethics. Each patient was informed of the nature of the study and signed the informed consent form.

Detection of LBP, sCD14, and hs-CRP

Blood samples were obtained after an overnight fast. Analyses were performed on sera frozen at −70°C. LBP was determined by a solid-phase enzyme-linked immunosorbent assay based on the sandwich principle (Hycult Biotechnology, Uden, Netherlands). The lower assay sensitivity limit was 1 ng/mL. Soluble CD14 (sCD14) was determined with an enzyme-linked immunosorbent assay (R&D Systems, Minneapolis, MN). The assay's lower detection limit for sCD14 was 0.125 ng/mL. For every sample, two analyses on the same plate were carried out and the mean value was used. Duplicate serum samples were taken from a subgroup of CD patients (n = 20), both at the time of relapse and after achieving remission (at 12 weeks), in order to investigate the intraindividual changes in serum LBP and sCD14 during flare-ups. hs-CRP levels were determined in all cases using the Integra 700 autoanalyzer system (Roche, Basel, Switzerland). The lower assay sensitivity limit was 0.1 mg/L. All of the assays were performed at the Department of Clinical Biochemistry and Molecular Pathology, University of Debrecen.

Detection of ASCA, anti-OMP, and pANCA

Serum IgG and IgA levels of ASCA and IgA antibody levels to bacterial outer membrane proteins (OMP) were evaluated separately, according to the manufacturer's protocol (ASCA IgG, ASCA IgA, QUANTA Lite, and OMP PLUS ELISA, INOVA Diagnostics, San Diego, CA). The results are presented as arbitrary units with a cutoff for positivity of 25 U/ml. Sera were documented both in absolute values and in frequency of positivity.

Determination of ANCA was performed by the indirect immunofluorescence technique using both ethanol- and formalin-fixed human peripheral blood neutrophil substrates (Nova Lite, INOVA Diagnostics).¹⁹ Sera were incubated at a 1:40 dilution for 30 minutes at room temperature, washed, and incubated according to the manufacturer's instructions with fluorescein isothiocyanate-labeled goat antihuman IgG. After incubation for 30 minutes at room temperature, the slides were washed. Examination and classification were preformed under ultraviolet light (UV) using a Leitz Wetzler (Germany) Leica indirect immunofluorescence microscope.

ANCA was considered as IBD-associated pANCA if it produced a broad nonhomogeneous rim-like staining of the nuclear periphery (with multiple intranuclear fluorescent foci) on ethanol-fixed human neutrophil substrates and little or no perinuclear or cytoplasmic staining on formalin-fixed neutrophils.

NOD2/CARD15 Genotyping

DNA Isolation

Genomic DNA was isolated from whole blood using the QIAamp DNA Blood Mini Kit (Qiagen, Munich, Germany).

Detection of NOD2/CARD15 SNP8, 12, 13 Mutations and TLR4 D299G Polymorphism

The NOD2/CARD15 SNP8, SNP12, and SNP13 genotypes and TLR4 D299G genotypes were known for all CD patients. NOD2/CARD15 variants were previously detected by denaturing high-performance liquid chromatography (dHPLC, Wave DNA Fragment Analysis System, Transgenomic, UK). Sequence variation, observed in the dHPLC profile, was sequenced on both strands to confirm the alteration. Sequencing reactions were performed with the ABI BigDye Terminator Cycle Sequencing Kit v. 1.1 (Applied Biosystems, Foster City, CA) and samples were sequenced on an ABI Prism 310 Genetic Analyzer (Applied Biosystems). The D299G polymorphism was detected by polymerase chain reaction/restriction fragment length polymorphism (PCR-RFLP) and fragments were separated and visualized by gel electrophoresis (3% NuSieve GTG agarose gel BMA, Rockland, ME). All investigated polymorphisms were in Hardy–Weinberg equilibrium (data not shown).

Statistical Methods

Variables were tested for normality using Shapiro Wilk's W-test. Hardy–Weinberg equilibrium test was performed by using Pearson's χ²-test, with one degree of freedom. A t-test with separate variance estimates, χ²-test, and χ²-test with Yates correction were used to evaluate differences between CD patients and controls, as well as within subgroups of CD patients. Pearson and Spearman SRO tests were used to analyze the association between continuous variables. To test the accuracy and cutoff values for LBP, sCD14, and hs-CRP, receiver operating characteristics (ROC) curves were generated by plotting sensitivity versus 1-specificity. Sensitivities, specificities, positive predictive values (PPV), and negative predictive values (NPV) were calculated to determine the predictive power of LBP, sCD14, and hs-CRP in distinguishing between active and inactive CD. Kaplan–Meier survival curves were plotted in order to analyze the association between hs-CRP, LBP, and sCD14, and clinical flare-up during follow-up with LogRank and Breslow tests. Additionally, forward stepwise Cox-regression analysis was used to assess the association between categorical clinical variables and time to clinical relapse. P < 0.05 was considered significant. For statistical analysis SPSS15.0 (SPSS, Chicago, IL) was used.

Results

Association Between Serum LBP and sCD14 and Disease Activity in CD

Of the 214 CD patients, 65 were clinically active, while 149 were inactive according to CDAI at the time of the blood draw. The mean serum LBP level was significantly higher (CDactive = 34,484, CDinactive = 26,227 versus controls = 19,333 ng/mL, P < 0.0001 for both) while sCD14 was lower in both active and inactive forms of disease as compared to the controls (CDactive = 1784, CDinactive = 1361 versus controls = 2159 ng/mL, P = 0.013 and P < 0.0001, Fig. 1).

In the group of 20 patients who were evaluated both at the time of relapse (median CDAI = 244; interquartile range [IQR]: 180–294) and during remission (CDAI = 73; IQR: 38–109), LBP (33,167; IQR: 23,170–41,821 ng/mL versus 14,446; IQR: 14,546–23,729, P < 0.001) and sCD14 (1969; IQR 1592–2670 ng/mL versus 1213; IQR: 1101–1441 ng/mL, P = 0.002) levels decreased in patients achieving clinical remission after 12 weeks (Fig. 2). The median hs-CRP (34.7; IQR 8.6–75.5 g/L versus 2.6; IQR: 1.1–7.1 g/L, P = 0.001) was also significantly decreased.

There was a significant correlation between LBP (R = 0.57 and R = 0.49, P < 0.001 for both), sCD14 (R = 0.37 and R = 0.19, P = 0.003 and P = 0.015, by Spearman SRO correlation) and hs-CRP levels in both active and inactive CD. At the same time, serum LBP and sCD14 levels were not different in patients with and without ASCA IgG/IgA, pANCA, and anti-OMP IgA antibodies or the combination of antimicrobial antibodies or pANCA-/ASCA+ or NOD2/CARD15 or TLR4 D299G mutation carriers and noncarriers (data not shown).

Diagnostic Accuracy of LBP, sCD14, and hs-CRP

The accuracy, determined by ROC analysis, of hs-CRP (AUC = 0.66), sCD14 (AUC = 0.70) was comparable for identifying patients with active disease (CDAI >150), while the accuracy of LBP (AUC = 0.58) was lower. In contrast, LBP (AUC = 0.79) was the best marker in selecting patients with elevated hs-CRP (5 mg/mL) in ROC analysis (Fig. 3). The markers' accuracy increased if the cutoff value of CRP was set to 10 mg/L (AUC CDAI = 0.72, sCD14 = 0.71, and LBP = 0.80).

Cutoff values were calculated from the ROC analysis for LBP. Based on the proposed cutoff values, the sensitivity and specificity of the different markers were calculated. Table 2 shows the predictive power of each individual marker and for the combination of the markers in distinguishing between active and inactive CD. Of note, the best accuracy for CRP was detected at 11.6 mg/L based on the ROC analysis, with a sensitivity of 59% and a specificity of 78.4%.

Association Between LBP, sCD14, and Disease Phenotype in Patients with CD

In inactive CD, serum LBP was associated with disease behavior (Fig. 4). The highest serum level was detected in CD patients with the penetrating form. No other clinically important associations were found between LBP and sCD14 level and disease phenotype in either active or inactive disease. In addition, LBP and sCD14 levels were not associated with medical therapy, smoking, or need for surgery (data not shown).

Association Between Laboratory Markers and Clinical Relapse in CD Patients

Of the 91 patients in remission, 21 (23%) relapsed during the 1-year follow-up. The predictive power of hs-CRP (>10 mg/L), LBP (>22,650 ng/mL) or sCD14 (>1395 ng/mL) and the combination of the markers for the identifying clinical relapse was calculated (Table 3). The best individual marker was LBP (odds ratio [OR]: 6.5; 95% confidence interval [CI]: 2.2–19.5, P = 0.001) and sCD14 (OR: 4.3;95% CI: 1.5–11.9, P = 0.004). When any two markers were positive, the relative risk of relapse was 11.8 (95% CI: 3.4–41.2) in univariate analysis.

In a Kaplan–Meier analysis, hs-CRP (P_LogRank = 0.016, P_Breslow = 0.019), LBP (P_LogRank < 0.001, P_Breslow < 0.001), and sCD14 (P_LogRank = 0.004, P_Breslow = 0.005) were significantly associated with clinical relapse (CDAI >150, ΔCDAI >100 and change in medical therapy) within 12 months (Fig. 5). Moreover, the combination of these markers (P_LogRank < 0.001, P_Breslow < 0.001) and a high relapse frequency in the past (>1/year during full follow-up, P_LogRank = 0.036, P_Breslow = 0.028), but not gender, location, behavior, current medical therapy (e.g., steroid use, immunosuppressive use, or biological use), need for previous surgeries, or smoking were significant determinants for the time to clinical relapse.

To further evaluate the effect of the above variables on the probability of clinical relapse, we performed a forward stepwise proportional Cox-regression analysis. LBP, sCD14, and a high relapse frequency, but not hs-CRP, were independently associated with the probability of clinical relapse (Table 4).

Discussion

This is the largest study that simultaneously assessed the clinical accuracy of LBP, sCD14, and hs-CRP in patients with CD. The present study demonstrated that LBP and sCD14 are markers of disease activity in CD, having similar accuracy as hs-CRP. In addition LBP, sCD14, but not hs-CRP, were independent predictors of clinical relapse during a 1-year follow-up.

In the present study the sensitivity, specificity, PPV, and NPV values for the individual markers (hs-CRP, LBP, and sCD14) to identify active disease, however, were moderate, with the highest sensitivity being for sCD14 and highest specificity for hs-CRP at a cutoff value of 10 mg/L. We also found a correlation between hs-CRP and CDAI. The coefficient of correlation between hs-CRP and the disease activity score was 0.36 in a previous study involving 90 CD patients,²⁷ while our corresponding value was 0.32. In addition, we calculated the accuracy of the combination of these markers. Three-marker-positivity was associated with a 76% PPV (OR_{active disease}: 4.66, 95% CI: 2.34–9.29) for identifying patients with active disease (CDAI >150), while all-marker-negativity ruled out active disease with an NPV of 91% (OR_{active disease}: 0.18, 95% CI: 0.06–0.51). Accordingly, the parallel detection of these simple markers may be more useful in the diagnosis of active CD than the individual ones.

In the present study, sCD14 levels in the sera were in the range previously reported,²¹ while LBP levels were higher in controls as well as in active and inactive adult CD patients. In the study by Pastor Rojo et al,²¹ the LBP level was 7200, 12,900, and 23,100 ng/mL in controls, inactive, and active CD, respectively. The characteristics of disease activity were comparable and could not explain these differences. The mean CDAI values were 84 versus 62 in inactive, while 235 versus 260 in active disease in the Spanish study, which is similar to the present study. Similarly, CRP values were comparable in active disease (40 versus 32 mg/L).

Our results can add new pieces to the puzzle of CRP elevation in CD. We found that the elevated levels of endotoxin-related markers—LBP and sCD14—were closely correlated to hs-CRP. Since our patients had no signs of active infection or abscesses, this supports the notion that bacteria passing through the transmurally inflamed gut wall could be the source of endotoxemia in active CD. These findings are in line with the hypothesis that bacteremia due to the translocation of the gut microbes may be one of the inductors of CRP synthesis during disease flare-up.⁶ In inactive CD the serum LBP level was significantly higher when compared to the healthy controls. This was mainly seen in penetrating (and to a lesser extent in the inflammatory) forms of the disease, indicating bacterial translocation even with a lack of overt disease activity signs. LBP was also reported to be a marker of small bowel bacterial translocation in other diseases.²⁸, ²⁹ Of note, LBP-LPS complexes induce the production of TNF-α, IL-6, and IL-8 and both CRP and LBP are early acute-phase proteins further induced by IL-1, IL-6, and TNF-α.¹² Increased permeability has been shown to be more common in small bowel CD than in colonic CD.³⁰ Nevertheless, in the present study we did not find any association between hs-CRP, LBP, and sCD14 levels and the affected site in either inactive or active CD. Similarly, LBP and sCD14 levels were not associated with the medication type, smoking, or need for surgery, in concordance with previous results.²¹

In some genetic studies an association was found between the risk for CD and the presence of variant SNPs in the CD14 gene through interaction with polymorphisms in the NOD2/CARD15 gene.¹⁵, ^17,NOD2/CARD15 is a member of the intracellular pattern recognition receptors, playing a key role in bacterial sensing, with mutations in the gene associated with the risk for CD.³¹ Moreover, an apparent link was reported between increased gut permeability and the NOD2/CARD15 3020insC mutation.³² Our group recently proposed that the serological response to various microbial antigens might be a universal marker of the enhanced translocation of the gut microflora through the impaired small bowel mucosa in different diseases accompanied by inflammation of the small bowel.³³, ³⁴ In the present study we did not find an association between LBP, sCD14 levels, and the presence of major NOD2/CARD15 SNPs or ASCA/anti-OMP antibodies in either active or inactive disease. However, the mechanism of LBP elevation and antimicrobial antibody formation in CD is different. LBP elevation might reflect acute bacterial translocation, and is confirmed by the simultaneous changes in disease activity, even in individual cases. In accordance with the findings of the Spanish study,²¹ we also demonstrated a drop in LBP, sCD14, and hs-CRP in patients having achieved remission through active medical treatment. On the contrary, the presence of antimicrobial antibodies in CD patients is relatively constant during the course of the disease and is independent of disease activity³⁵; therefore, they are rather a sign of a chronic process involving a sustained systemic exposure to the constituent of the gut microflora.

In the present work we demonstrated that serum markers are also useful to predict clinical relapses in patients with clinical remission. The combination of the markers was superior to individual ones. Based on our data, patients with a positive result for any 2–3 markers had a high probability for a clinical relapse (PPV 87%–95%) in the subsequent 12-month period. Some years ago, the GETAID group⁶ proposed a simple biological score for predicting short-term (6-week) relapse. Multivariate analysis selected two predictive markers for relapse: CRP >20 mg/L and ESR >15 mm/h. The score's sensitivity and specificity were 89% and 43%, respectively. Of note, however, there are some substantial differences between the GETAID and the present studies. The treatment was homogenous in the GETAID study. After steroid-induced remission, patients received only mesalamine maintenance therapy. In contrast, the present study was performed in a referral IBD population and the results may be generalized to IBD populations having a relatively high exposure to immunosuppressive and biological agents. This dissimilarity is clearly reflected in the relapse rates (54% in the GETAID study versus 23% in the present study). In addition, we used 10 mg/L cutoff levels for CRP, based on the results of the ROC analysis. The 20 mg/L cutoff used in the GETAID study was disproportionately high, while the cutoff value for ESR (15 mm/h) was less well explained. Moreover, the accuracy of the individual markers was, in general, close to that of the composite score.

A recent population-based study by the IBSEN group⁶ has also demonstrated that CRP at diagnosis or during follow-up was able to predict medium-term outcome, using a different and more solid endpoint, resective surgery. A significant association between CRP levels at the time of diagnosis and the risk for surgery was found only in CD patients with terminal ileitis (L1), with the risk increasing in this subgroup when CRP levels were above 53 mg/L (OR 6.0, 95% CI: 1.1–31.9). The accuracy of the marker, however, was not tested in a multivariate analysis, thus the confounding effect of some important factors (e.g., behavior) cannot be excluded. In the present study, hs-CRP was not an independent predictor of 1-year clinical relapse in a Cox regression model. These all suggest that hs-CRP tends to be a short-term marker of disease activity. In contrast, serum levels of LBP, sCD14, and a high previous relapse rate were independently associated with time to clinical relapse during the subsequent 12 months, making them medium-term markers of disease activity. This latter finding confirms the data of Munkholm et al,³⁶ who reported a positive correlation between the rate of relapse within the first 3 years after diagnosis and the relapse rate in the following 5 years. In addition, the relapse rate during 1 year influenced the relapse rate in the following year. Of note, serum LBP level was associated with height Z-score at the timepoint of blood draw in a pediatric study.²² In this study the clinical disease activity was also assessed during follow-up, and the frequency of moderate-to-severe clinical disease activity did not differ between the groups over the first 24 months following diagnosis. This later finding, however, is difficult to interpret since results of patients with active and inactive disease at the initial investigation were merged. Moreover, the definition of high and low LBP was arbitrary; CD patients were stratified by median LBP concentration; however, ROC analysis was not performed.

We are aware of the limitations of our study. First, CRP is widely used in CD, since it shows acceptable correlation with disease activity delineated/defined by clinical indices²³ and also endoscopic or histological activity²⁶, ³⁷ and in the present study endoscopic/histological activity was not assessed. Instead, we used a more vigorous, composite endpoint—as suggested also by the recent position paper by the International Organization for Inflammatory Bowel Diseases³⁸—to identify clinically relevant relapses (CDAI >150, ΔCDAI >100, and change in medical therapy) beyond the use of CDAI only, which is known to correlate poorly with the result of endoscopic or histological activity.³, ³⁹ By doing this we tried to mimic the everyday clinical decision-making algorithm, where clinicians have to rely in most cases on clinical symptoms and laboratory tests during follow-up. Of note, in the studies by Jones et al³⁹ and Schoepfer et al³ CRP or hs-CRP was the second best marker for the detection of endoscopically active disease, but how LBP and sCD14 perform in terms of predicting mucosal inflammation in patients in clinical remission was not studied. Nonetheless, in spite of circumstantial evidence it is still unclear whether mucosal healing prevents the development of complications. Second, a close correlation was reported recently between fecal neutrophil marker calprotectin and the simple endoscopic score (SES-CD) and clinical relapses and in some studies.³, ³⁹, ⁴⁰ Since fecal markers (e.g., calprotectin) are more sensitive for inflammation in the colon, it would be interesting to compare and combine the predictive power of these serum and fecal markers.

In conclusion, LBP and sCD14 are markers of disease activity in CD, showing an accuracy similar to that of hs-CRP. The good correlation between the levels of hs-CRP and endotoxin-related markers—LBP, sCD14—further supports the role of bacteremia that results from increased bacterial translocation in the inflammatory process of IBD. Moreover, LBP, sCD14, and a high frequency of previous relapses were independent predictors for a medium-term, clinical flare-up. Further studies are needed to investigate the predictive power of the above markers in prospective follow-up studies and well-selected patient cohorts.

References

Author notes