Assessment of secondary immunodeficiency – the role of laboratory testing

Abstract

Clinical immunology is in a historically significant phase of escalation of targeted immunotherapeutics that will continue to transform the management of immune mediated diseases. Each of these novel agents manipulates the immune system in different ways with adverse events including a spectrum of opportunistic infections, malignancies and paradoxical inflammatory reactions. A key clinical challenge for prescribers at the bedside is the selection and titration of the most suitable agents for maximum benefit and minimum toxicity. In this context, it is worth reviewing what has been achieved to date in measuring the functional immune reserve in an individual patient. At the simplest level immunodeficiency can be characterised by the susceptibility to infection. This approach presents two problems. First, infections are a universal experience of otherwise healthy individuals, and second, the prevention of episodes of infection is a key clinical ambition. Conventional immunopathology tests may provide data to help identify which patients are at greatest risk of immunosuppression complications, but when critically appraised, fall short of what is required in practice. This paper will review current laboratory approaches to assessing secondary immunodeficiency and will highlight the need for immunopathology laboratories to adapt to the new therapeutic opportunities.