Certain Immune Cells May Help Assess AAV Disease Activity

A blood parameter called large unstained cell count or LUC – which measures the numbers of certain activated immune cells – appears to associate with higher ANCA-associated vasculitis (AAV) disease activity, a small study found.

The study, “Clinical significance of large unstained cell count in estimating the current activity of antineutrophil cystoplasmic antibody-associated vasculitis,” was published in The International Journal of Clinical Practice.

A complete blood count or CBC is a blood test that provides information about the cells present in a person’s blood. It is often included as part of a health check-up.

Sometimes, an increased number of larger-than-normal cells, which are not stained with routine blood staining techniques (that is, colored using special dyes), is detected in a CBC. Those cells, known as LUCs, are thought to be activated white blood cells.

White blood cells, part of the body’s immune system, flow through the bloodstream to fight viruses, bacteria, and other foreign invaders. Therefore, alterations in the number of LUCs may be indicative of medical conditions marked by inflammation or a deranged immune response, as happens in AAV.

Now, researchers in Korea sought to explore whether the number of these enlarged cells is associated with greater disease activity in AAV, as measured with the Birmingham vasculitis activity score (BVAS).

If confirmed, LUC count could “be easily used as a novel index to promptly estimate the current activity of AAV in real clinical settings,” the researchers wrote.

The team examined the electronic medical records of 176 AAV patients – 64.8% of them women– with a median age of 61, who had never been treated with immunosuppressants. The majority (60.2%) had microscopic polyangiitis, followed by granulomatosis with polyangiitis (28.4%), and eosinophilic granulomatosis with polyangiitis (11.4%).

Overall, 60.2% of these patients tested positive for LUCs. Their median LUC count was 60 cells per cubic millimeter of blood. The median BVAS was 12, but patients with LUCs had greater median BVAS scores than those in whom LUCs were not detected (14 vs. 10).

Statistical analyses demonstrated that the LUC count significantly correlated with BVAS, meaning that the higher the LUC count, the higher the disease activity. LUC count also correlated with other blood parameters, including total white blood cell count, hemoglobin (the oxygen-carrying protein in the blood), and C-reactive protein (a marker of inflammation that is often increased in AAV patients).

To examine if LUC count could predict high disease activity, the researchers then divided the patients into three groups according to their BVAS scores. That helped the team to define high disease activity as a BVAS of 15 or greater.

Using a LUC count of 15 cells per cubic milliliter as a cut-off, the researchers were able to correctly identify about 71.4% of patients with high disease activity (sensitivity) and 50.9% of those with lower BVAS scores (specificity).

Also, patients with a high LUC count – equal to or greater than 15 immune cells per cubic millimeter of blood – were significantly more likely to have high disease activity than those with lower LUC counts. Indeed, those with higher LUC counts were about 2.6 times more like than patients with low counts to have high disease activity.

However, when multiple variables were examined at the same time, neither the presence of LUCs nor a high LUC count were significantly associated with disease activity.

Nevertheless, the researchers concluded that, in AAV patients, the “LUC count was significantly correlated with the current BVAS and [a high LUC count] could estimate the current high BVAS.”