Combined diagnostic criteria help classify AAV types in children
Study: System has potential to help accurately categorize pediatric cases
Combining two diagnostic systems used to classify cases of ANCA-associated vasculitis (AAV) in adults improved classification performance in a pediatric AAV patient population, according to a study in China.
Identifying types of AAV is important to ensure effective clinical care in children, researchers noted.
“Considering that distinct clinical types of AAV are associated with varying risks of organ damage, clinicians should tailor their focus to specific types of organ damage based on clinical classification,” researchers wrote.
Their combination system has the potential to help clinicians accurately categorize pediatric cases, but larger studies are needed to confirm the superiority of the new system.
The study, “Performance of EMA algorithm, 2022 ACR/EULAR criteria, and EMA-ACR/EULAR algorithm in classifying pediatric ANCA-associated vasculitis: a national cohort study in China,” was published in the World Journal of Pediatrics.
Clinicians typically classify AAV cases into three types
In AAV, the immune system wrongly produces self-reactive antibodies that ultimately cause inflammation and damage to small blood vessels. This damage tends to be more severe in pediatric forms of AAV.
Upon considering symptoms and molecular features of the disease, clinicians typically classify AAV cases into three types and tailor treatment appropriately.
In microscopic polyangiitis (MPA), kidney damage is common and masses of immune cells, called granulomas, don’t appear near inflamed areas. Granulomas are a feature of the two other AAV types: granulomatosis with polyangiitis (GPA) and eosinophilic granulomatosis with polyangiitis (EGPA).
GPA typically results in symptoms involving the lungs, kidneys, and ear, nose, and throat (ENT). People with EGPA tend to mostly have symptoms in the lungs and gastrointestinal tract.
Two primary diagnostic frameworks help clinicians distinguish between AAV types: the European Medicines Agency (EMA) algorithm and the 2022 American College of Rheumatology (ACR)/European Alliance of Associations for Rheumatology (EULAR) classification criteria.
The EMA algorithm is structured to ensure cases only receive one classification, while the ACR/EULAR criteria can result in multiple classifications, which is a potential disadvantage. However, the ACR/EULAR criteria include information reflecting updated understandings of AAV relative to the EMA algorithm. For example, it includes results from blood tests regarding the type of AAV-triggering self-reactive antibody, which can help identify disease type.
Both diagnostic frameworks were designed with adults in mind, potentially limiting their applicability in children.
New research should target symptoms not captured by adult diagnostic criteria
In this study, a team of researchers China aimed “to explore suitable classification criteria for pediatric patients based on the existing classification criteria for adults.”
Specifically, they created the EMA-ACR/EULAR algorithm, which combined the step-by-step process of the EMA algorithm with criteria of the ACR/EULAR system, including antibody findings. They then assessed its performance compared with each classification system.
“This new approach aims to resolve the issue of duplicate classification present in the 2022 ACR/EULAR criteria and to refine the existing EMA algorithm,” the researchers wrote.
The multicenter study included 179 children in China who received an AAV diagnosis at a mean age of 10.1 years. Regardless of which classification criteria the team used, most had MPA, followed by GPA. All three systems yielded a subset of participants (7.8% to 16.2%) who remained unclassified.
When comparing the EMA algorithm to the ACR/EULAR criteria, the latter system resulted in fewer unclassified cases, as it classified about half of the EMA unclassified cases. The ACR/EULAR criteria also reclassified a number of EMA-classified cases. These changes were likely attributable to antibody test results. Four children met both MPA and GPA criteria under the ACR/EULAR system.
Both systems found higher ENT involvement in children with GPA compared with MPA, but significantly poorer kidney function in those with MPA.
To predict the prognosis of AAV patients, it is also necessary to comprehensively consider clinical manifestations, [disease-associated] features, and biological indicators to build a more accurate risk prediction model.
Statistical analysis indicated that the newly created EMA-ACR/EULAR algorithm outperformed each of the other systems individually. However, 15.1% of the children remained unclassifiable.
This may indicate “that children with unique or mild symptoms are still in the prediagnosis state based on adult diagnostic criteria, so these criteria may not be fully applicable to pediatric patients,” the researchers wrote.
Further research could focus on these potential early pediatric symptoms not captured by adult diagnostic criteria to expedite diagnosis.
Because kidney involvement in AAV can negatively impact prognosis, the team compared the risk of developing kidney failure across disease types in the three diagnostic systems.
They found that a greater proportion of children with MPA developed kidney failure under all three diagnostic frameworks relative to children with GPA. This difference, however, only reached statistical significance with the EMA algorithm.
A joint EMA-ACR/EULAR framework was effective for classifying most pediatric cases, but future studies in larger groups and in populations from other parts of the world are needed need to validate this finding.
Regardless of the diagnostic system, clinical assessment of AAV should be holistic, the team noted.
“To predict the prognosis of AAV patients, it is also necessary to comprehensively consider clinical manifestations, [disease-associated] features, and biological indicators to build a more accurate risk prediction model,” the researchers concluded.
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