A time-adjusted cortisol cut-off can reduce referral rate for Synacthen stimulation test whilst maintaining diagnostic performance

Suzanne Brown, Narelle Hadlow, Imran Badshah, David Henley

    Research output: Contribution to journalArticle

    2 Citations (Scopus)

    Abstract

    Objective: Cortisol cut-offs can predict requirement for Synacthen stimulation tests (SST). We assessed the performance of a standard cortisol cut-off (375 nmol/L) across the morning and compared this with a time-adjusted cut-off. Design: Retrospective audit. Patients: Community reference set (n=12 550) and SST patients (n=757). Measurements: In the reference population, time-specific cortisol medians were calculated and used to convert cortisol to time-adjusted Multiples of the Median (MoM). In 757 SST patients, the predictive performance of a standard cortisol cut-off (375 nmol/L) and its time-adjusted MoM equivalent were compared. Results: Median cortisol decreased by ~30 nmol/L per hour between 0700 and 1200h. In the reference population, proportions below the 375 nmol/L cut-off increased throughout the morning (range 35%-64%), whereas using the time-adjusted MoM cut-off proportions were consistent (range 46%-50%), with a 17% maximal difference in referral rates between the two cut-offs after 1100h. A similar pattern was noted in the SST cohort. When a cortisol MoM cut-off was used to predict SST success, the excess proportion of patients tested and misclassification rates were lower and more consistent than when the standard cut-off was used. A median cortisol of 375 nmol/L equated to 444 and 313 nmol/L before 0800 and after 1100 h, respectively. Conclusion: The use of a standard cortisol cut-off results in 17% more patients being referred for SST later in the morning. A time-adjusted cortisol cut-off provides consistent and lower referral rates, whilst maintaining similar or better performance than a standard single cut-off in predicting outcome of SST.

    Original languageEnglish
    Pages (from-to)418-424
    Number of pages7
    JournalClinical Endocrinology
    Volume87
    Issue number5
    DOIs
    Publication statusPublished - 1 Nov 2017

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    title = "A time-adjusted cortisol cut-off can reduce referral rate for Synacthen stimulation test whilst maintaining diagnostic performance",
    abstract = "Objective: Cortisol cut-offs can predict requirement for Synacthen stimulation tests (SST). We assessed the performance of a standard cortisol cut-off (375 nmol/L) across the morning and compared this with a time-adjusted cut-off. Design: Retrospective audit. Patients: Community reference set (n=12 550) and SST patients (n=757). Measurements: In the reference population, time-specific cortisol medians were calculated and used to convert cortisol to time-adjusted Multiples of the Median (MoM). In 757 SST patients, the predictive performance of a standard cortisol cut-off (375 nmol/L) and its time-adjusted MoM equivalent were compared. Results: Median cortisol decreased by ~30 nmol/L per hour between 0700 and 1200h. In the reference population, proportions below the 375 nmol/L cut-off increased throughout the morning (range 35{\%}-64{\%}), whereas using the time-adjusted MoM cut-off proportions were consistent (range 46{\%}-50{\%}), with a 17{\%} maximal difference in referral rates between the two cut-offs after 1100h. A similar pattern was noted in the SST cohort. When a cortisol MoM cut-off was used to predict SST success, the excess proportion of patients tested and misclassification rates were lower and more consistent than when the standard cut-off was used. A median cortisol of 375 nmol/L equated to 444 and 313 nmol/L before 0800 and after 1100 h, respectively. Conclusion: The use of a standard cortisol cut-off results in 17{\%} more patients being referred for SST later in the morning. A time-adjusted cortisol cut-off provides consistent and lower referral rates, whilst maintaining similar or better performance than a standard single cut-off in predicting outcome of SST.",
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    A time-adjusted cortisol cut-off can reduce referral rate for Synacthen stimulation test whilst maintaining diagnostic performance. / Brown, Suzanne; Hadlow, Narelle; Badshah, Imran; Henley, David.

    In: Clinical Endocrinology, Vol. 87, No. 5, 01.11.2017, p. 418-424.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - A time-adjusted cortisol cut-off can reduce referral rate for Synacthen stimulation test whilst maintaining diagnostic performance

    AU - Brown, Suzanne

    AU - Hadlow, Narelle

    AU - Badshah, Imran

    AU - Henley, David

    PY - 2017/11/1

    Y1 - 2017/11/1

    N2 - Objective: Cortisol cut-offs can predict requirement for Synacthen stimulation tests (SST). We assessed the performance of a standard cortisol cut-off (375 nmol/L) across the morning and compared this with a time-adjusted cut-off. Design: Retrospective audit. Patients: Community reference set (n=12 550) and SST patients (n=757). Measurements: In the reference population, time-specific cortisol medians were calculated and used to convert cortisol to time-adjusted Multiples of the Median (MoM). In 757 SST patients, the predictive performance of a standard cortisol cut-off (375 nmol/L) and its time-adjusted MoM equivalent were compared. Results: Median cortisol decreased by ~30 nmol/L per hour between 0700 and 1200h. In the reference population, proportions below the 375 nmol/L cut-off increased throughout the morning (range 35%-64%), whereas using the time-adjusted MoM cut-off proportions were consistent (range 46%-50%), with a 17% maximal difference in referral rates between the two cut-offs after 1100h. A similar pattern was noted in the SST cohort. When a cortisol MoM cut-off was used to predict SST success, the excess proportion of patients tested and misclassification rates were lower and more consistent than when the standard cut-off was used. A median cortisol of 375 nmol/L equated to 444 and 313 nmol/L before 0800 and after 1100 h, respectively. Conclusion: The use of a standard cortisol cut-off results in 17% more patients being referred for SST later in the morning. A time-adjusted cortisol cut-off provides consistent and lower referral rates, whilst maintaining similar or better performance than a standard single cut-off in predicting outcome of SST.

    AB - Objective: Cortisol cut-offs can predict requirement for Synacthen stimulation tests (SST). We assessed the performance of a standard cortisol cut-off (375 nmol/L) across the morning and compared this with a time-adjusted cut-off. Design: Retrospective audit. Patients: Community reference set (n=12 550) and SST patients (n=757). Measurements: In the reference population, time-specific cortisol medians were calculated and used to convert cortisol to time-adjusted Multiples of the Median (MoM). In 757 SST patients, the predictive performance of a standard cortisol cut-off (375 nmol/L) and its time-adjusted MoM equivalent were compared. Results: Median cortisol decreased by ~30 nmol/L per hour between 0700 and 1200h. In the reference population, proportions below the 375 nmol/L cut-off increased throughout the morning (range 35%-64%), whereas using the time-adjusted MoM cut-off proportions were consistent (range 46%-50%), with a 17% maximal difference in referral rates between the two cut-offs after 1100h. A similar pattern was noted in the SST cohort. When a cortisol MoM cut-off was used to predict SST success, the excess proportion of patients tested and misclassification rates were lower and more consistent than when the standard cut-off was used. A median cortisol of 375 nmol/L equated to 444 and 313 nmol/L before 0800 and after 1100 h, respectively. Conclusion: The use of a standard cortisol cut-off results in 17% more patients being referred for SST later in the morning. A time-adjusted cortisol cut-off provides consistent and lower referral rates, whilst maintaining similar or better performance than a standard single cut-off in predicting outcome of SST.

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    KW - cut-offs

    KW - multiples of the median

    KW - synacthen stimulation test

    KW - time-adjusted

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    DO - 10.1111/cen.13405

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