The utility of the corticotropin test to diagnose adrenal insufficiency in critical illness: an update

ObjectiveOne of the most common dynamic testing procedures for assessment of adrenocortical function is the standard corticotropin or the cosyntropin test. The aim of this review was to examine the evidence base underlying the corticotropin test in the management of the critically ill patient. Data synthesisThe principle behind the corticotropin test is the demonstration of an inappropriately low cortisol production in response to exogenous ACTH, a situation analogous to physiological stress. The corticotropin test was originally described in nonstressed subjects, and its applicability and interpretation in the setting of critical illness continues to generate controversy. Attempting to determine the prevalence of an abnormal corticotropin test in critical illness is complicated by the use of different end-points and different populations. Moreover, the test result is also influenced by the assay used for measurement of plasma cortisol. Trials assessing the relationship between corticotropin response and severity of stress and organ dysfunction have produced divergent results, which may reflect differences in the methodology and the association being measured. Moreover, controversy exists with respect to the methodology and the interpretation with respect to the following variables: dose of corticotropin, end-points for assessment of total or free cortisol, effect of plasma cortisol variability, adrenal blood flow and its equivalence with other tests of adrenocortical function. ConclusionsThe corticotropin test is used widely in the evaluation of adrenocortical function in the endocrine clinics. Its role in the critically ill patient is less well established. Several confounding variables exist and to have a one-size-fits-all' approach with a single end-point in the face of several methodological and pathophysiological confounders may be flawed and may result in the institution of inappropriate therapy. The current evidence does not support the use of the corticotrophin test in critical illness to assess adrenocortical function and guiding steroid therapy in critical illness.