Routine blood tests may help doctors track AAV activity, study finds
Blood cell patterns distinguished active disease from remission
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Blood cell ratios derived from routine blood tests may help distinguish people with active ANCA-associated vasculitis (AAV) from those in glucocorticoid-free remission, independent of age and sex, according to a new study.
“Our findings suggested that these readily available, standardized, low-cost biomarkers make them attractive candidates for integration into routine monitoring protocols,” the researchers wrote.
The study, “Inflammatory blood count ratios discriminate disease activity and remain persistently elevated during glucocorticoid-free remission in ANCA-associated vasculitis,” was published in Clinical and Experimental Medicine.
AAV can damage small blood vessels
Most AAV cases are caused by the immune system’s production of self-targeting antibodies, called ANCAs, that overactivate neutrophils, a type of white blood cell. This ultimately results in inflammation and damage to small blood vessels, which can affect multiple organs, but most often the kidneys, lungs, and upper airways.
In this study, researchers in Italy examined whether ratios of different blood cell types, calculated from a routine blood test, could distinguish active disease from remission, a period with no signs of disease activity.
“Although immune profiling has proven useful in other autoimmune diseases, reliable immune signatures reflecting AAV activity remain poorly defined,” the researchers wrote.
The team collected blood samples from 99 adults with ANCA-positive AAV (50.5% women; median age, 60) who were followed at the Padua Vasculitis Center, in Italy. A group of 258 healthy volunteers (27.9% women; median age, 47) served as a control group.
In terms of AAV types, 75 participants had granulomatosis with polyangiitis, while 24 had microscopic polyangiitis. No patients were receiving treatments known to greatly affect circulating blood cell profiles, including glucocorticoids, which are potent anti-inflammatory medications often used in AAV.
Disease activity was measured using the validated Birmingham Vasculitis Activity Score, known as BVAS. Most patients (71.7%) were in remission (a BVAS score of zero and an absence of disease symptoms), while 28 (28.3%) had active disease (a BVAS greater than zero).
Blood cell ratios higher in active AAV
Researchers measured three blood cell ratios: the neutrophil-to-lymphocyte ratio (NLR), the platelet-to-lymphocyte ratio (PLR), and the monocyte-to-lymphocyte ratio (MLR). Monocytes and lymphocytes are immune cells, while platelets are the cell fragments that help blood clot.
According to blood tests, all three ratios were significantly higher in active AAV patients than in those in remission: NLR (4.4 vs. 2.6), PLR (202.9 vs. 151.2), and MLR (0.56 vs. 0.37). After accounting for age and sex, these ratios remained significantly higher, by about 1.4 to two times.
Notably, both AAV groups showed significantly higher NLR, PLR, and MLR compared with healthy controls.
Among patients, higher values across all three ratios were significantly associated with higher BVAS scores, indicating greater disease activity. Higher NLR and PLR values, but not MLR, also significantly correlated with increased blood levels of C-reactive protein (CRP), a marker of body-wide inflammation. With respect to disease history, higher ratios were associated with a shorter disease duration at the time of blood sampling.
Within the remission group, AAV patients receiving maintenance immunosuppressive therapy had a significantly higher PLR than those not on immunosuppression, whereas NLR was similar between groups.
Also in this group, higher NLR and MLR correlated with greater organ damage, as assessed by the Vasculitis Damage Index. No significant associations were detected between the ratios and disease duration or time since glucocorticoid or immunosuppressive therapy discontinuation.
Ratios may help distinguish disease activity
The researchers then used statistical models to assess the ratios’ discriminative potential between AAV patients with active disease and those in remission. They found that NLR performed best, with an area under the curve, or AUC, of 0.818; AUC values range from zero to one, with higher values indicating greater discriminative potential. That was followed by PLR (AUC, 0.795) and MLR (AUC, 0.684).
“We showed that [blood cell] inflammatory ratios derived from routine complete blood counts may complement existing clinical assessment tools in AAV by capturing aspects of immune activation not fully reflected in clinical disease activity scores,” the team wrote. “Future … studies [following patients over time] will be crucial to further define their role across different treatment settings and to explore their prognostic relevance.”
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