Sialic Acid as a Suitable Marker of Clinical Disease Activity in Patients With Crohn's Disease

Yaoming Chen, MB; Yuting He, MM; Xiaoxia Zhan, PhD; Dubo Chen, MB; Pinning Feng, MB; Yan Yan, MB; Yichong Wang, PhD


Lab Med. 2022;53(4):381-385. 

In This Article

Abstract and Introduction


Objective: Elevated serum levels of sialic acid (SA) have been verified in patients with various inflammatory conditions. The association between the Crohn's disease (CD) activity and serum SA has been insufficiently studied.

Materials and Methods: Serum SA concentrations were determined using an enzymatic colorimetric assay method, and the correlation of SA with the Harvey-Bradshaw Index (HBI) and other inflammation activity markers was evaluated using the Spearman correlation. The predictive value of SA in estimating CD disease activity was assessed using the receiver operating characteristic.

Results: The SA levels were positively correlated with HBI and C-reactive protein (CRP) levels. The correlation of SA with the HBI was superior to that of CRP with the HBI. The area under the curve for SA was higher than that for CRP, with an optimal cutoff value of 53.14 mg/dL for active CD.

Conclusion: Serum SA correlates with the HBI score better and has better predictive value in monitoring CD disease activity than CRP or other inflammatory markers.


Crohn's disease (CD) is 1 type of chronic nonspecific inflammatory bowel disease (IBD) whose etiologies remain unclear.[1] To date, there is no way to cure it completely. Consequently, medical treatment aims to maintain CD disease activity within remission.[2,3] The determination of disease activity is a crucial factor in the diagnosis and treatment of CD. In current clinical practice, a combination of methods is used when identifying CD disease activity, including symptom assessment, colonoscopy, histological and radiographic evaluation, and multiple laboratory markers.[4,5]

Endoscopic examination with biopsies is considered the gold standard for evaluating CD activity, but it is limited because of its invasiveness and the risk of multiple complications.[6,7] The Harvey-Bradshaw Index (HBI) is a simplified version of the Crohn's disease activity index (CDAI) that was developed in 1980[8,9] and is used to monitor the clinical disease activity of patients with CD. However, the HBI score has limitations, such as being time-consuming and based on self-reporting for measuring clinical characteristics.[10]

C-reactive protein (CRP) and the erythrocyte sedimentation rate (ESR) are 2 of the most commonly used serum indexes to estimate CD activity. However, the specificity and sensitivity of these 2 indexes are unsatisfactory.[11–13] A low albumin (ALB) level is often linked with the severity of inflammation but is also affected by infection and nutritional status.[14] Almost all current serological biomarkers have limitations of nonspecificity. Fecal calprotectin has a far greater accuracy for detecting intestinal inflammation than serum biomarkers. However, it requires collecting a fecal specimen, which is time-consuming and more suitable to differentiate IBD from irritable bowel syndrome.[15,16] Based on the above information, it is crucial to seek a noninvasive marker of disease activity with high sensitivity and specificity, which will be key to monitoring the presence of active disease.

Sialic acid (SA) is a kind of 9-carbon monosaccharide that presents in human serum and tissues with multiple and critical cell biological functions.[17–19] Research has shown that SA is an acute phase reactant, and it has been observed to increase in several inflammatory disorders, such as rheumatoid arthritis.[20] To date, there are only a few small-sample studies on the properties of SA in distinguishing CD disease occurrence or CD disease activity.[21,22] Furthermore, none of the studies have analyzed the association between SA and the HBI score.

Therefore, our present study analyzed the relationship between serum SA and the HBI score, compared the validity of SA with other disease activity markers in clinical practice, and estimated the predictive value of SA in CD disease activity. This study aims to ascertain whether serum SA could serve as a useful index of disease activity in patients with CD.