Serum Biomarkers and Musculoskeletal Ultrasound for Assessment of Disease Activity in Patients With Juvenile Idiopathic Arthritis During Tocilizumab Therapy

Abstract

Polyarticular JIA (p-JIA), as defined by ILAR, refers to arthritis involving five or more joints within the first 6 months of the disease. This subgroup is further classified into two categories: rheumatoid factor (RF) positive or RF negative. The RF-positive category refers to individuals who have tested positive for RF on two or more tests, with at least 3 months between each test, within the first 6 months [1].

Given the growing prevalence of Polyarticular JIA (p-JIA) treatment, TCZ has emerged as a primary biologic agent [2]. Consequently, there is a rising demand for an innovative and reliable biomarker that can be utilized for the detection and monitoring of disease activity while undergoing IL-6 blockade therapy. TCZ has demonstrated the ability to impede IL-6R signaling, resulting in a rapid decrease in C-reactive protein (CRP) levels. Therefore, CRP may not serve as a dependable indicator for monitoring disease activity while undergoing TCZ treatment [3].

Serum amyloid A (SAA) and serum calgranulin C (S100A12) serve as reliable indicators of both local and systemic inflammation due to its production by inflammation-involved cells and has a systematic spill. It is a more dependable indicator than CRP or ESR for tracking disease progression in different rheumatic and autoinflammatory conditions, such as JIA, particularly in the age of biologic immunosuppressive treatment [4, 5].

The utilization of MSUS has proven to be a valuable method in assessing p-JIA. It allows for the visualization of inflammatory lesions prior to permanent joint damage, in addition to the monitoring of disease progression as well as treatment outcomes [6].

The objective of this study was to determine the significance of serum markers (amyloid A and calgranulin C) and musculoskeletal ultrasound in assessing disease activity in polyarticular JIA cases who are undergoing TCZ therapy.

This study involved 100 patients diagnosed with polyarticular JIA (p-JIA) based on the International League of Associations for Rheumatology (ILAR) [1] criteria for JIA. Subjects were categorized into two groups according to the line of treatment for 3 months (Group I: 50 patients with p-JIA on TCZ therapy; Group II: 50 patients with p-JIA on conventional DMARDS [c-DMARDS]). Additionally, 50 apparently healthy age and sex-matched children served as controls. Patients were recruited from the Rheumatology Department's Outpatient Clinic at Tanta University Hospitals. Exclusion criteria were other types of JIA, other biological therapy, infection, and malignancy. All participants provided informed consent, and the study received approval from the Local Research Ethical Committee, Faculty of Medicine, Tanta University (approval code No: 34276/11/20).

Patients underwent the following: (1) Disease activity evaluation, using JADAS 27 [7]. (2) Laboratory investigations included ESR, hs-CRP, serum ferritin, CBC, RF, SAA, and S100A12 using ELISA technique [8]. (3) Musculoskeletal ultrasonography, including sonographic examination utilizing SAMSUNG MEDISON (UGEO H60) at (9–13 MHz) linear array transducers. A total of 50 joints for each subject (right and left shoulders, elbows, wrists, metacarpophalangeal (MCP) joints, proximal interphalangeal (PIP) joints, distal interphalangeal (DIP) joints, hips, knees, ankles, and metatarsophalangeal joints) were scanned with both B-mode Ultrasound and Doppler Ultrasound [9].

Data were analyzed using SPSS (Statistical package for the social sciences) version 20.

The clinical and demographic data, laboratory investigations, and MSUS findings are depicted in Table 1. There were substantial differences between p-JIA patients and controls regarding ESR, hs-CRP, serum ferritin, SAA, and S100A12 (p < 0.001*).

The addition of serum S100A12, SAA, and PDUS score resulted in a sensitivity of 95.24% and specificity of 81.82%, allowing for the differentiation between active and remission cases (the area under the curve [AUC] was calculated to be 0.871 [95% CI 0.805–0.937]). The serum level of S100A12 at a threshold of 74.4 ng/mL demonstrated an AUC 0.894 (95% CI 0.836–0.953, sensitivity 95.24%, and specificity 81.82%), SAA alone at cutoff of 11.23 mg/L AUC was 0.877 (95% CI 0.812–0.941, sensitivity 86.90%, and specificity 80.30%) while PDUS score at cutoff of 6 AUC was 0.867 (95% CI 0.799–0.934, sensitivity 83.33%, and specificity 80.30%).

The relation between hs-CRP and SAA, S100A12 levels, as well as US activity in both groups, is summarized in Table 2. In Group I, no notable association was observed between hs-CRP and JADAS 27, SAA, S100A12, and US scores. As regards, the correlation of SAA and S100A12 were significantly correlated with JADAS 27, ESR, serum ferritin, and US scores in both JIA groups (p < 0.001). Multivariate logistic regression analysis for factors predictive of disease activity in group 1 revealed that SAA (B = 0.802, p < 0.001), S100A12 (B = 0.954, p < 0.001), and US (B = 0.754, p < 0.001) scores could be used as significant predictive factors for disease activity in p-JIA patients during tocilizumab therapy.

Previous studies have revealed that p-JIA is distinguished by the presence of autoreactive antigen-specific T cells and elevated levels of autoantibodies. Naive T-cell differentiation into Th cells, triggered by IL-1B, leads to the generation of the pro-inflammatory cytokine IL-17. This cytokine, in turn, may stimulate IL6, MMP1, and 3, IL8 production by synoviocytes, thereby causing joint destruction [10] TCZ restores CRP to a normal level by binding to IL-6R and suppressing IL-6 activity [11].

Our current study showed a significant reduction in SAA levels in Group I compared to Group II, while there was a significant increase in serum SAA levels in both groups compared to controls. This finding agrees with El-Bahnasawy et al. [12] who studied SAA levels in patients with JIA and documented that their levels were higher in patients than in healthy controls. Consistent with our findings, Soric’ Hosman et al. [5] documented that TCZ led to a dramatic and rapid drop in SAA levels to normal compared with more traditional treatments, such as methotrexate. Furthermore, they reported that the decline in disease activity and SAA levels is more significant in patients receiving anti-IL-6 than those receiving anti-TNFα therapy.

Upon analyzing the S100A12 levels in our subjects, we detected a notable reduction in S100A12 levels in Group I compared to Group II. These findings align with Tronconi E et al. [13], who discovered that S100A12 levels are considerably greater in individuals with active Sjogren's syndrome. However, in patients receiving TCZ, the levels of S100A12 are reduced compared to those who did not receive TCZ.

During the MSUS examination, 50 joints were evaluated in each patient from both groups. Mosa DM et al. [14], studied 40 joints in 60 patients with JIA and concluded that MSUS is a highly sensitive method for detecting synovitis, tenosynovitis, and erosive bone disease, and it helps to make proper therapeutic decisions.

SSA and S100A12 levels significantly correlated with JADAS 27, ESR, serum ferritin, and US scores in TCZ therapy patients.

This result is consistent with Orczyk K and Smolewska E [15], who found that S100A12 concentrations increased in JIA. Patients with disease flare exhibited the highest values. There was a strong correlation between the concentrations of S100A12 and JADAS27 as well as the levels of ESR. Al-Bassam, Ad'hiah and Mayouf [16] showed a significant correlation between S100A12 and ferritin levels.

Our study demonstrated that S100A12 exhibited higher sensitivity and specificity compared to SAA and the total US score. All three markers proved to be effective indicators for monitoring disease activity in children with JIA.

These findings align with Wittkowski et al. [17] and Aljaberi et al. [18], who discovered that S100A12 levels aid in confirming the diagnosis of JIA and facilitate early distinction from severe systemic infections as well as various malignant and inflammatory disorders. Therefore, S100A12 serves as a vital laboratory biomarker, exhibiting greater sensitivity and specificity compared to other available indicators of inflammation.

This study has limitations; therefore, a larger patient sample and a longitudinal study design are recommended to validate the findings and assess the effects of administered drugs.

In conclusion, SAA and calgranulin C are considered more sensitive markers than hs-CRP for monitoring treatment response with TCZ in polyarticular JIA patients. Moreover, musculoskeletal ultrasound can be used as an assessment tool to monitor disease progression and treatment response in JIA patients.

All the authors participated in the conception of the work, methodology, draft preparation, edition, and final approval.

The authors declare no conflicts of interest.