Redefining ITT cortisol thresholds on Abbott platforms to prevent misdiagnosis of adrenal insufficiency.

BACKGROUND: Adrenal insufficiency (AI) is a life-threatening condition which requires long term glucocorticoid replacement. The insulin tolerance test (ITT) is the current gold standard test for diagnosis of secondary AI, but the widely accepted cut-off value of a peak cortisol of less than 500 nmol/L assumes that anyone who does not reach this value has AI and thus requires full replacement. The cut-off used to diagnose AI is also founded on outdated assays. Use of this cut-off in an era of more specific immunoassays therefore risks misdiagnosis, subsequent unnecessary glucocorticoid exposure and associated adverse effects with increased mortality risk. DESIGN, PATIENTS AND MEASUREMENTS: This retrospective analysis assessed 300 ITT cortisol responses using the Abbott Architect and Alinity analyser platforms in patients with suspected AI over a period of 12 years (August 2010 to January 2022), at a tertiary centre. RESULTS: Patients were classified as having AI or not, based on a comprehensive clinical review of electronic patient records from the point of test to the present day by a panel of pituitary and adrenal specialists. Using the current institutional cut-off value of 500 nmol/L, receiver operating characteristic analysis identified a 100.0% sensitivity and 43.6% specificity (area under the curve 0.979). Using a lower cortisol threshold value of 416 nmol/L on the Abbott analyser platform maintained a sensitivity of 100.0% and improved the specificity to 86.7%. CONCLUSION: This data supports lowering the Abbott analyser ITT peak cortisol threshold to 416 nmol/L. Use of this improved cut-off avoids unnecessary glucocorticoid replacement therapy in 104 (34.7%) of individuals in this study. All patients remained well with at least 1 year longitudinal follow up of glucocorticoid replacement.

The irrelevant sound effect under articulatory suppression: is it a suffix effect?

An experiment is reported that investigates the relation between the suffix effect and the effect of irrelevant sound on the serial recall of short sequences of spoken material. The main issue was whether there is an effect of irrelevant sound under articulatory suppression in the presence of a spoken suffix. As in Hanley and Bakopoulou (2003), the irrelevant sound comprised speech that was presented during the retention interval. When a spoken suffix appeared at the end of the list, a significant effect of irrelevant sound remained when participants were able to rehearse list items. However, it disappeared under articulatory suppression. The effects of irrelevant sound remained significant under suppression when the suffix was an auditory tone but was confined to the final position of the serial position curve. These results parallel those reported by Jones, Macken, and Nicholls (2004) and Jones, Hughes, and Macken (2006) when they examined the effect of articulatory suppression on the phonological similarity effect. The results are consistent with Jones et al.'s (2006, 2004) view that an acoustic-perceptual representation of the terminal list items is the source of the effects of irrelevant sound and phonological similarity when they occur in the presence of articulatory suppression.