Routine blood tests may help doctors monitor AAV inflammation
Study finds markers appear to increase when disease is more active
Written by |
Inflammation markers calculated from routine blood tests, such as ratios of different types of immune cells and a combined inflammation index, appear to increase when ANCA-associated vasculitis (AAV) is more active, a study found.
Even though these markers are not specific to AAV, they “may serve as potential supportive markers for assessing disease activity,” the researchers wrote.
The study, “New inflammatory markers associated with disease activity in patients with antineutrophil cytoplasmic antibody-associated vasculitis,” was published in Clinical and Experimental Medicine.
In AAV, the immune system mistakenly attacks the small blood vessels, causing inflammation that can damage organs, most commonly the kidneys.
The Birmingham Vasculitis Activity Score (BVAS) “is the most commonly used tool for AAV disease activity assessment,” but “its application efficiency in actual clinical scenarios is affected by the differences between observers and the complicated assessment process, leading to reduced clinical operability,” the researchers wrote. That means “clinical research needs to find biomarkers that can objectively reflect the disease activity of AAV,” they said.
How do immune cells change with inflammation?
The researchers, in China, looked at whether inflammation markers calculated from routine blood tests can reflect how active AAV is. Similar to previous studies, it focused on newer markers that reflect changes in immune cells during inflammation.
These included the monocyte-to-lymphocyte ratio (MLR), neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), and systemic inflammation response index (SIRI). The SII considers neutrophils, lymphocytes, and platelets, whereas SIRI considers monocytes, lymphocytes, and neutrophils.
Monocytes, lymphocytes, and neutrophils are immune cells, and platelets are blood cell fragments involved in blood clotting.
The team retrospectively analyzed data from 974 adults with AAV. Disease activity was measured using the BVAS, and patients were divided into a high-disease-activity group (BVAS 12 or higher) and a low-disease-activity group (BVAS lower than 12).
Age and sex distributions were similar between the two groups, but people with high disease activity had more frequent involvement of the kidneys, lungs, cardiovascular system, and abdomen. They also had significantly higher BVAS (18.6 points vs. 6.6 points) and a worse prognosis based on the Five-Factor Score (2.1 points vs. 1.4 points), which predicts outcomes in people with systemic, or body-wide, inflammation of the blood vessels.
Patients with more active disease had significantly higher MLR, NLR, PLR, SII, and SIRI than those with low disease activity.
Because kidney problems may be a sign of severe AAV, the researchers compared inflammation markers between patients with and without kidney involvement. They found that those with kidney involvement had significantly higher BVAS as well as higher MLR, NLR, SII, and SIRI.
To see how AAV treatment affected inflammation, the team looked at data from 310 patients before and after treatment. They found that the traditional inflammation markers, C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), were significantly reduced after treatment. SII and SIRI also showed significant reductions with treatment, indicating reduced inflammation.
Correlation analysis showed that all five inflammation markers rose as the BVAS, CRP, and ESR increased. This means that higher levels of these markers were linked to more active disease. An increase in all markers, except PLR, was also significantly associated with a higher Five-Factor Score, indicating a worse prognosis.
After adjusting for factors such as age, sex, type of AAV, kidney involvement, and ESR, three markers — MLR, NLR, and SIRI — remained independently linked to disease activity.
Overall, the findings indicated that “the new inflammatory markers increased significantly in the patients with high AAV disease activity and in those with [kidney] involvement,” the researchers wrote. “MLR, NLR, PLR, and SIRI were identified as risk factors for severe AAV.”
While these markers are not disease-specific, they are simple, inexpensive tools that may help doctors monitor inflammation and guide clinical decisions, the researchers said. “Whole blood cell count is one of the most commonly used blood tests in clinics,” the team wrote.
Still, “given the single-center, retrospective design and the absence of a control group, these results should be interpreted with caution,” they concluded, calling for validation studies.
