In patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) who are suspected of having an infection, T lymphocyte subsets and immunoglobulin (Ig) and complement levels can be used as diagnostic markers and guides for appropriate treatment, according to findings from a cross-sectional study published in Clinical and Experimental Medicine.

In patients with AAV, infection is the leading cause of death. AAV is characterized as a group of chronic autoimmune disorders associated with blood inflammation. It can be caused by several factors, including infection, genetics, and environmental issues. With the development of infection common among patients with AAV, effective indicators predictive of infections are critical in this population.

The investigators sought to describe the features of infectious events reported among individuals with newly diagnosed AAV, including the following:

  • T lymphocyte subsets: CD3+ T cells, CD3+CD4+ T cells, and CD3+CD8+ T cells, along with the ratio of
    CD3+CD4+ T cells:CD3+CD8+ T cells
  • Ig levels: IgG, IgM, and IgA
  • Complement levels: C3 and C4

A total of 280 patients newly diagnosed with AAV between January 2014 and December 2020 at the First Affiliated Hospital of Zhengzhou University in China were enrolled in the study. AAV activity among the participants was assessed with the Birmingham Vasculitis Activity Score (BVAS). Prognosis at diagnosis was evaluated with the Five-Factor Score (FFS).

Of the 280 participants with AAV, 91 were coinfected and 189 were uninfected. Significantly higher white blood cell counts, neutrophil counts, and BVAS, along with lower lymphocyte counts, were reported in the infected group (P ≤.001 for all). No significant difference in FFS was observed between the groups.

Infection was defined as “having symptoms of infection (fever, cough, sputum production, etc.), positive microbiological culture (sputum, alveolar lavage fluid, blood, and other body fluids), or imaging evidence.” The most common type of infection reported was pulmonary infection.

The average levels of the following parameters were significantly lower in the infected group compared with the uninfected group:

  • CD3+ T cell counts: 720.0 vs 920.5, respectively; P <.001
  • CD3+CD4+ T cell counts: 392.0 vs 547.0, respectively; P <.001
  • CD3+CD8+ T cell counts: 248.0 vs 335.0, respectively; P =.001
  • Serum IgG levels: 11.66 g/L vs 13.59 g/L, respectively; P =.002
  • Serum IgA levels: 1.70 g/L vs 2.44 g/L, respectively; P <.001
  • Serum C3 levels: 1.03 g/L vs 1.09 g/L, respectively; P =.015
  • Serum C4 levels: 0.24 g/L vs 0.27 g/L, respectively; P <.001

Per multivariate analysis in which adjustments were made for confounders, the following parameters were independent risk factors for infection:

  • CD3+CD4+ T cell counts: adjusted odds ratio [aOR], 0.997; 95% CI, 0.995-1.000; P =.018
  • Serum IgG levels: aOR, 0.804; 95% CI, 0.692-0.933; P =.004
  • Serum C4 levels: aOR, 0.001; 95% CI, 0.000-0.215; P =.013

“Patients [with] infected AAV and those without infection differ in T lymphocyte subsets and immunoglobulin and complement levels,” the authors noted. “When infection is suspected [in individuals with AAV, these measures] . . . may be used as indicators for differential diagnosis and formulation of individualized treatment,” they concluded.

Reference

Liu R, Li M, Zhang L, Wang Y, Li W, Liu S. T lymphocyte subsets and immunoglobulin and complement levels are associated with the infection status of patients with antineutrophil cytoplasmic antibody-associated vasculitis. Clin Exp Med. Published online February 19, 2023. doi:10.1007/s10238-023-01021-4

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