How good is a morning cortisol in predicting an adequate response to intramuscular synacthen stimulation?

Abstract

Basal morning cortisol is a viable first step in the evaluation of patients with suspected adrenal insufficiency.

Adrenal insufficiency in non‐transfusion‐dependent α‐thalassemia

“…Moreover, in the Iran study, morning cortisol ≥6.2 μg/dL was defined as normal adrenal function. This cut‐off is low compared with a previous study that evaluated adrenal function after central nervous system insults (pituitary tumor, cranial radiation, and neurosurgery) and after insults due to other causes using morning cortisol cut‐offs 7.7 μg/dL (85% sensitivity, 71% specificity) and 8.5 μg/dL (84% sensitivity, 71% specificity), respectively . In the present study, the prevalenceof biochemical AI in ITT‐confirmed α‐thalassemia was 31%.…”

Validated criteria for the interpretation of a single measurement of serum cortisol in the investigation of suspected adrenal insufficiency

“…We have targeted 95% sensitivity in order to enable comparison with recently published literature. 6,7,17 Our data demonstrate NPV is very high using this threshold, although because of the dependence of NPV on pretest probability, caution is required in those with a particularly high index of clinical suspicion. Although setting a higher sensitivity would come at the expense of a greater proportion of patients requiring confirmatory testing, we found cut-offs of <308 and <312 nmol/L would achieve 99% and 100% sensitivity, respectively, for morning samples.…”

“…We have targeted 95% sensitivity in order to enable comparison with recently published literature . Our data demonstrate NPV is very high using this threshold, although because of the dependence of NPV on pretest probability, caution is required in those with a particularly high index of clinical suspicion.…”

“…Previous efforts to define similar thresholds for basal serum cortisol have produced values which vary widely. [6][7][8][9][10][11][12][13][14][15][16][17][18] Assay variability plays a significant role in limiting the ability to define unified criteria.…”

“…A single measurement of serum cortisol as an initial step in the investigation of AI therefore carries a number of advantages over dynamic testing. Although extensively studied, [6][7][8][9][10][11][12][13][14][15][16][17][18] this remains a contentious approach, and reports of its diagnostic utility, and suggested thresholds, vary considerably. This may reflect challenges in interpreting single measurements of serum cortisol due to its circadian and ultradian variability, 19 assay variation, 17 and the relative rarity of the condition relative to the size of the population tested, meaning a large cohort is required to draw reliable conclusions.…”