Advancements in Non-Invasive Biomarkers for Crohn’s Disease

Introduction

Crohn’s disease (CD) is a chronic, multifactorial intestinal disorder characterized by relapsing and remitting symptoms, currently without a definitive cure. Its global incidence and prevalence are rising, leading to significant health burdens.

The clinical symptoms of CD are diverse, including gastrointestinal issues like abdominal pain and diarrhea, and systemic manifestations. Pathologically, it is marked by chronic inflammation, mesenteric thickening, fistulas, and abscesses. A critical therapeutic aim is mucosal healing (MH), defined as the resolution of intestinal inflammation and ulceration. However, assessing MH post-treatment typically involves invasive procedures such as endoscopy and tissue biopsy.

Given the invasiveness and impracticality of frequent re-evaluations, there is a need for non-invasive diagnostic tools. Such advancements would enhance disease management and outcome prediction.

Role of Blood-Based Biomarkers in Crohn’s Disease

Serological markers offer a non-invasive means to evaluate CD activity due to their objective nature and minimal invasiveness. Traditional markers like C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are widely used. However, they are not specific, as they can be elevated in various inflammatory conditions.

Recent research has introduced new biomarkers with improved specificity. One such marker is the neutrophil-to-pre-albumin ratio (NPAR), which demonstrates value in predicting inflammatory bowel disease (IBD) activity. Another promising marker is the C-reactive protein to albumin ratio (CAR), which integrates CRP and albumin levels to assess CD activity.

Additional blood-based parameters such as the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), lymphocyte-to-monocyte ratio (LMR), and lymphocyte-to-CRP ratio (LCR) are being recognized for their potential in assessing inflammatory disease activity and prognosis, including in oncology.

The Systemic Immune-Inflammation Index (SII)

The systemic immune-inflammation index (SII) is a promising serological marker that quantifies systemic inflammatory responses by combining neutrophil, platelet, and lymphocyte counts. Studies have demonstrated SII’s utility in prognostic assessments of autoimmune inflammatory conditions and tumor outcomes.

Research by Wu et al. showed a strong correlation between SII levels and inflammatory status in ankylosing spondylitis patients, suggesting SII’s superior discriminative capability for disease activity compared to conventional markers like CRP and ESR. Further, Lin et al.’s study indicated that SII outperforms other inflammation markers in predicting active ulcerative colitis. These findings suggest SII’s potential value in CD prognosis.

Current Study on CD Biomarkers

A recent study comprehensively evaluated and compared multiple inflammatory markers to assess CD activity, severity, and predict MH after treatment. The study included 259 CD patients from April 2012 to December 2023, with data collected from the Second Affiliated Hospital of Nanchang University.

Exclusion criteria included other IBD diagnoses, active infections during treatment, and incomplete blood test data. Patient groups were stratified based on the simplified Crohn’s disease activity index (CDAI), also known as the Harvey-Bradshaw index, into remission, mild activity, or moderate-severe activity.

Data were collected at initial admission and再度 evaluated after treatment. Specifically, MH was assessed through endoscopic examinations, following one to six months of therapy, to classify patients into mucosal healing (SES-CD =0–2) or non-mucosal healing groups (SES-CD ≥ 3).

Analysis and Key Findings

The study analyzed various blood parameters, including NLR, PLR, LMR, SII, CAR, and LCR. The least absolute shrinkage and selection operator (LASSO) regression was used to identify the most relevant predictors. Multivariate logistic regression analysis was applied to construct predictive models for disease progression.

Using ROC curve analysis, the study found that SII was the most accurate marker for predicting CD activity, demonstrating an AUC of 0.774, and it performed even better in predicting disease severity, with an AUC of 0.807. Other biomarkers like PLR, NLR, LMR, LCR, CAR, CRP, and ESR were evaluated for their predictive accuracy.

When assessing MH, the study revealed that LCR provided the best predictive performance with an AUC of 0.794.

Development of a Predictive Nomogram

Based on LASSO and multivariate logistic regression, the study constructed nomograms for predicting CD activity, severity, and MH. These nomograms incorporated variables such as CRP, ESR, SII, PLR, and LCR to predict prognosis accurately.

The predictive nomograms demonstrated good calibration and clinical utility, confirmed by calibration analysis and decision curve analysis (DCA). These tools offer clinicians a reliable basis for assessing patient progression.

Discussion and Future Directions

The study highlights SII as a significant independent prognostic factor associated with CD activity and severity. Consistently integrating SII with established markers like CRP and ESR enhances predictive accuracy. Routine blood tests supplemented by SII-based nomograms can provide initial disease progression assessments.

Despite SII’s promising results, the study acknowledges limitations such as incomplete serological data for some patients and a limited sample size. Future research should include larger, diverse patient populations to ascertain the robustness of SII in predicting long-term outcomes.

Improvements in clinical scoring indices can reduce bias and variability in disease assessments. Additionally, integrating inflammatory biomarkers with advanced imaging modalities may offer a more comprehensive and objective evaluation of disease progression.

Conclusion

SII is a pivotal biomarker for evaluating inflammatory activity and severity in CD. A prognostic nomogram incorporating SII has been established, offering a dependable tool for tracking CD progression. Serological markers, including SII and LCR, provide a non-invasive means to anticipate MH following treatment.

Data Sharing Statement

The data supporting this study are available from the corresponding author upon reasonable request.

Ethical Statement

Patient data is used solely for scientific research purposes. Without explicit patient consent, no identifying information will be disclosed.

Acknowledgments

The authors thank Xifu Cheng for technical support in statistical analysis.

Funding

This work was supported by grants from the National Natural Science Foundation of China and the Natural Science Foundation of Jiangxi Province.

Disclosure

The authors report no conflicts of interest.

References

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