N-glycans unlocking the secrets of Ankylosing Spondylitis

Unlocking Ankylosing Spondylitis: Can IgG N-Glycans Be the Key to Earlier Diagnosis?

Lena Kashyap in Health & Wellness October 2026 • 4 min read.

"New research identifies novel serum biomarkers that could revolutionize the detection and management of this chronic inflammatory disease."

Ankylosing spondylitis (AS) is a persistent inflammatory condition that currently lacks definitive cures and clear understanding of its causes. The diagnostic process for AS is often prolonged, averaging 6–8 years, which can significantly delay appropriate treatment and management. HLA-B27, while commonly used, suffers from low specificity, as it appears in other arthritic conditions. This creates a significant need for more reliable biomarkers to aid in the early and accurate diagnosis of AS.

The role of IgG glycosylation in immune-related disorders is well-documented, with specific IgG glycoforms known to maintain immune balance. While altered IgG glycosylation is observed in autoimmune and inflammatory conditions, identifying specific glycan biomarkers on IgG for AS has remained a challenge. Recent research has focused on addressing this gap, aiming to pinpoint unique glycan signatures that could serve as diagnostic markers for AS.

Building on prior work that developed a specialized microfluidic chip to quantify low-abundance acidic glycans, researchers have now applied this technology to analyze serum IgG in AS patients. This innovative approach has led to the identification of potential N-glycan biomarkers that show promise in distinguishing AS from healthy individuals, offering a new avenue for improved diagnostic strategies.

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Standard Approach

IgG N-Glycans as Emerging AS Biomarkers

The cited AS study reports that the average delay in diagnosis is 6–8 years and identifies HLA-B27 as a key laboratory marker, while noting that it is also present in people with other conditions, including reactive arthritis and psoriatic arthritis. Using serum IgG glycomic analysis, researchers selected 11 neutral and 6 acidic N-glycans as potential AS classification biomarkers. The study describes this as the first use of this glycomic approach to identify potential N-glycan biomarkers for AS, building on earlier work that found two sulfated N-glycans promising for seronegative rheumatoid arthritis. Developing IgG N-glycan biomarkers for autoimmune diseases is described as a laborious, time-consuming effort requiring multidisciplinary collaboration.

Decoding IgG N-Glycans: Potential Biomarkers for Ankylosing Spondylitis

N-glycans unlocking the secrets of Ankylosing Spondylitis

The study involved eighty patients with definite AS, meeting the modified New York criteria (1984), alongside eighty age- and gender-matched healthy controls. Researchers analyzed individual N-glycan levels in serum samples, evaluating them as classification variables. The sample set was divided equally into a training and validation group. Feature selection methods identified eleven neutral and six acidic N-glycans as potential biomarkers.

Two N-glycans, namely 5_5_1_0 and 6_5_0_3-a, showed particularly high prediction capacity for AS. The area under the curve (AUC), sensitivity, and specificity were all greater than 70% in both the training and validation sets. A combination of these two N-glycan biomarkers yielded even better results, with higher AUCs (0.823 and 0.911), sensitivities (75% and 86.5%), and specificities (82.1% and 80.8%) observed in the training and validation groups, respectively.

5_5_1_0 and 6_5_0_3-a: These two N-glycans showed the most promise as biomarkers.
High Prediction Capacity: Both glycans demonstrated AUC, sensitivity, and specificity above 70%.
Combined Biomarkers: Combining the two glycans further improved diagnostic accuracy.

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Latest Research

Evidence and Open Questions in Biomarker Research

A 2025 case–control study describes noninvasive IgG N-glycan assays as offering high accuracy for AS diagnosis and prognosis, though the supplied source excerpt does not provide performance figures. A 2021 review reports that anti-SIRT1 autoantibodies were higher in AS and psoriatic arthritis patients, but not rheumatoid arthritis patients, compared with controls in one study. The supplied AS biomarker report notes a 6–8-year average diagnostic delay and identifies HLA-B27 as a key laboratory marker, while also reporting that it occurs in other conditions. Separately, a study of 389 patients with systemic lupus erythematosus and 304 healthy controls identified two serum IgG N-glycans as diagnostic biomarkers for lupus; that finding concerns SLE, not AS.

Univariate analysis revealed significant differences in the levels of these markers between control and AS groups, but not in patients with psoriatic arthritis (PsA). There was a correlation between glycan 5_5_1_0 levels and erythrocyte sedimentation rate (ESR), with more significant reduction observed in the subgroup with elevated ESR. Influence from impurity (IgA and IgM) was proven to be slight (<5%).

The Future of AS Diagnosis: N-Glycans as Novel Biomarkers

This study introduces N-glycan-based biomarkers for AS, demonstrating relatively high sensitivity and specificity for AS classification. The identified biomarkers, derived predominantly from IgG, have potential roles in immune homeostasis and inflammation.

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Broader Context

Promise and Challenges of Glycan Biomarkers

A 2023 review examines IgG N-glycan profiles as potential diagnostic tools, cohort discriminators, and prognostic biomarkers. It discusses recent successes, remaining challenges, and approaches expected to shape future work. The review frames these profiles as an evolving research area rather than a settled solution.

Real-World Impact

Diagnosis and Disease-Activity Assessment

A study published on February 22, 2025, describes axial spondyloarthritis (axSpA) as an inflammatory rheumatic disease that presents challenges in diagnosis and disease-activity assessment. It says that IgG N-glycosylation alterations have been observed across various rheumatic diseases, while their role in axSpA remained unclear, and sets out to examine glycan profiles in relation to diagnosis and disease activity. A separate source dated September 15, 2025, likewise says empirical evidence linking IgG N-glycosylation, inflammatory factors, and ankylosing spondylitis was sparse and describes an investigation of those associations and the diagnostic performance of IgG glycosylation traits. The supplied AS report gives an average diagnostic delay of 6–8 years.

Given the critical role of IgG N-glycans in immune regulation and inflammation, these biomarkers could serve as valuable tools for characterizing disease phenotypes, predicting treatment responses, and providing new insights into the pathogenesis of AS. Further studies are anticipated to explore the roles of N-glycans in AS on a larger scale.

In conclusion, the study suggests that incorporating N-glycan analysis into diagnostic protocols could significantly improve the early detection and management of ankylosing spondylitis. This offers new avenues for personalized medicine approaches and potentially more effective treatment strategies.

Study at a glance
Population	Patients with definite ankylosing spondylitis and age-matched, gender-matched healthy volunteers^[1]
Setting	Three hospitals in China^[1]
Comparison	Age-matched and gender-matched healthy volunteers^[1]
Effect size	Combined biomarkers: AUCs 0.823 and 0.911, sensitivities 75% and 86.5%, and specificities 82.1% and 80.8% in training and validation sets, respectively^[1]
p-value	p=0.0001 for correlation between glycan 5_5_1_0 and ESR^[1]
Times cited	6^[1]

How later work and related markers compare

The paper’s comparison with psoriatic arthritis found no significant alteration in the two selected markers, which narrows the claim beyond a simple contrast with healthy controls without establishing performance across other conditions.^[2]

What follow-up studies would need to clarify

Would these markers retain their classification performance in broader patient groups that include people with other inflammatory or rheumatic conditions?^{[1] [2]}
Would larger studies reproduce the observed association between glycan 5_5_1_0 and ESR, and clarify how it relates to disease activity?^{[1] [2]}
Can glycan-based classification add information beyond HLA-B27, whose limited specificity is described in the source paper?^{[1] [2]}

Terms used in the glycan study

AUC: Area under the curve^[2]
ESR: Erythrocyte sedimentation rate^[2]

Sources

Serum IgG N-glycans act as novel serum biomarkers of ankylosing spondylitis (Elsevier BV, 2019)
Serum IgG N-glycans act as novel serum biomarkers of ankylosing spondylitis (Europe PMC, 2019)

About this Article -

Written with AI assistance from published research, and reviewed by the Mystum team. See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1136/annrheumdis-2018-213815, Alternate LINK

Title: Serum Igg N-Glycans Act As Novel Serum Biomarkers Of Ankylosing Spondylitis

Subject: General Biochemistry, Genetics and Molecular Biology

Journal: Annals of the Rheumatic Diseases

Publisher: BMJ

Authors: Jingrong Wang, Canjian Wang, Yong Liang, Hudan Pan, Zhihong Jiang, Zhanguo Li, Yuhui Li, Liangyong Xia, Wei Liu, Xiao Zhang, Zhilong Liu, Min Jiang, Ju Liu, Hua Zhou, Liang Liu

Published: 2018-11-15

Everything You Need To Know

1

What is Ankylosing spondylitis and why is early diagnosis so important?

Ankylosing spondylitis (AS) is a chronic inflammatory condition characterized by the absence of definitive cures and a limited understanding of its causes. Early diagnosis is crucial but often delayed due to the reliance on biomarkers such as HLA-B27, which lacks specificity. The diagnostic process can take 6–8 years, leading to delayed treatment. The identification of reliable biomarkers, such as IgG N-glycans, is therefore vital for improving patient outcomes by enabling earlier and more accurate diagnoses.

2

What are IgG N-glycans and how are they related to this condition?

IgG N-glycans are sugar molecules attached to the IgG antibodies, playing a role in the body's immune response. Their glycosylation patterns can shift in various diseases. Recent research indicates that specific IgG N-glycans could serve as biomarkers for AS. These unique glycan signatures, particularly 5_5_1_0 and 6_5_0_3-a, were identified using a microfluidic chip, offering a more precise method for diagnosis than currently available tools. These biomarkers' potential lies in their ability to differentiate AS from healthy individuals with higher sensitivity and specificity, therefore improving patient management.

3

Which specific N-glycans were identified as potential biomarkers, and what were the results?

The study identified two N-glycans, specifically 5_5_1_0 and 6_5_0_3-a, as promising biomarkers for Ankylosing spondylitis (AS). These were found to have high prediction capacity, with an area under the curve (AUC), sensitivity, and specificity above 70% in both the training and validation sets. The combination of these two IgG N-glycans showed even better results, further improving the diagnostic accuracy. These findings suggest that these specific N-glycans could be critical in the early and accurate identification of AS, which has implications for treatment plans and patient outcomes.

4

What is the significance of using the microfluidic chip in this research?

The significance of using the microfluidic chip lies in its specialized design that can quantify low-abundance acidic glycans, providing precise measurements of specific N-glycans. This innovative approach has facilitated the identification of potential biomarkers. By analyzing serum IgG in AS patients, the technology helps to distinguish these patients from healthy controls. This method offers an advanced diagnostic strategy, differentiating it from traditional methods.

5

What are the key implications of this study's findings?

The implications of this research are substantial. The identified IgG N-glycans, particularly 5_5_1_0 and 6_5_0_3-a, offer a potential for earlier and more accurate diagnosis of AS. This could lead to timely treatment and better patient management. The study showed relatively high sensitivity and specificity for AS classification, which could improve outcomes. These findings also highlight the role of IgG glycosylation in immune homeostasis and inflammation, opening new avenues for research and potential therapeutic targets.