Evaluating laboratory criteria for combined immunodeficiency in adult patients diagnosed with common variable immunodeficiency.

Some patients diagnosed with common variable immunodeficiency (CVID) actually suffer from combined immunodeficiency (CID) and therefore may require a different, CID-adapted treatment. Several CD4 T-cell-based criteria have been proposed in the past to identify patients with CID within the cohort of adult CVID patients. In this monocentric study, we used retrospective immunological and clinical data of 238 CVID patients to compare four different proposals of how to define CID among CVID patients. We demonstrate that none of the current definitions sufficiently separates CID from CVID patients and that the relative reduction of naïve CD4 T cells <10% has the highest sensitivity of all tested markers for patients with clinical complications often associated with CID. Thus, a very low percentage of naïve CD4 T cells in any adult CVID patient should raise suspicion, but is not sufficient to define CID among CVID patients.