Specificity of late-night salivary cortisol measured by automated electrochemiluminescence immunoassay for Cushing's disease in an obese population

The conundrum of differentiating Cushing's syndrome from non-neoplastic hypercortisolism: a systematic review and meta-analysis

CONTEXT

Once hypercortisolemia is confirmed, differential diagnosis between Cushing's syndrome (CS) due to neoplastic endogenous hypercortisolism and non-neoplastic hypercortisolism (NNH, pseudo-Cushing's syndrome) is crucial. Due to worldwide corticotropin-releasing hormone (CRH) unavailability, accuracy of alternative tests to dexamethasone (Dex)-CRH, is clearly needed.

OBJECTIVE

Assess the diagnostic accuracy of Dex-CRH test, desmopressin stimulation test, midnight serum cortisol (MSC), and late-night salivary cortisol (LNSC) levels to distinguish CS from NNH.

METHODS

Articles through March 2022 were identified from Scopus, Web of Science, MEDLINE, EMBASE, and PubMed. All steps through the systematic review were performed independently and in duplicate and strictly adhered to the updated PRISMA-DTA checklist.

DATA SYNTHESIS

A total of 24 articles (1900 patients) were included. Dex-CRH had a pooled sensitivity and specificity of 91% (95%CI 87-94%; I2 0%) and 82% (73-88%; I2 50%), desmopressin test 86% (81-90%; I2 28%) and 90% (84-94%; I2 15%), MSC 91% (85-94%; I2 66%) and 81% (70-89%; I2 71%), and LNSC 80% (67-89%; I2 57%) and 90% (84-93%; I2 21%), respectively. Summary receiver operating characteristics areas under the curve were Dex-CRH 0.949, desmopressin test 0.936, MSC 0.942, and LNSC 0.950 without visual or statistical significance. The overall risk of studies bias was moderate.

CONCLUSION

Dex-CRH, the desmopressin stimulation test, and MSC have similar diagnostic accuracy, with Dex-CRH and MSC having slightly higher sensitivity, and the desmopressin test being more specific. LNSC was the least accurate, probably due to high heterogeneity, intrinsic variability, different assays, and lack of consistent reported cutoffs. When facing this challenging differential diagnosis, the results presented here should increase clinicians' confidence when deciding which test to perform.

Molecularly imprinted electrochemical aptasensor based on functionalized graphene and nitrogen-doped carbon quantum dots for trace cortisol assay

This paper proposes a novel electrochemical aptasensor that integrates molecular imprinting techniques for trace analysis of cortisol. This sensor is based on functionalized graphene and nitrogen-doped carbon quantum dots. The morphology and structure of the modified electrode were characterized by scanning electron microscopy and Raman spectroscopy. The functional monomer aptamer and the template molecule cortisol were adsorbed on the electrode by electrostatic adsorption to construct an imprinted sensing platform. Under the optimal conditions, such as the concentration of template molecule, the ratio of template to functional monomer, the elution and adsorption time, the sensor exhibits linearity and a low detection limit of 10^-12-10^-8 M and 3.3 × 10^-13 M, which is more sensitive than other reported cortisol analysis methods. In addition, this sensor can realize the determination of cortisol in salivary samples with high recovery values, showing great development potential in the field of life sciences.

Distinct Late-Night Salivary Cortisol Cut-Off Values for the Diagnosis of Hypercortisolism

Due to high morbidity and mortality of untreated hypercortisolism, a prompt diagnosis is essential. Measurement of late-night salivary cortisol provides a simple and non-invasive method. However, thresholds and reference ranges differ among studies. The goal of this study was to define a threshold of late-night salivary cortisol for the diagnosis of hypercortisolism based on the used assay. Moreover, the influence of different aetiologies of hypercortisolism and individual comorbidities were investigated. Prospective analyses of 217 patients, including 36 patients with proven hypercortisolism were carried out. A sum of 149 patients with suspicion of hypercortisolism but negative endocrine testing and 32 patients with hypercortisolism in remission served as control group. Late-night salivary cortisol was measured using an automated chemiluminescence immunoassay. Cut-off values were calculated by ROC analysis. The calculated cut-off value for the diagnosis of hypercortisolism was 10.1 nmol/l (sensitivity 94%; specificity 84%). Only slightly lower thresholds were obtained in patients with suspected hypercortisolism due to weight gain/obesity (9.1 nmol/l), hypertension or adrenal tumours (both 9.8 nmol/l) or pituitary adenomas (9.5 nmol/l). The late-night salivary cortisol threshold to distinguish between Cushing's disease and Cushing's disease in remission was 9.2 nmol/l. The cut-off value for the diagnosis of ectopic ACTH-production was 109.0 nmol/l (sensitivity 50%, specificity 92%). Late-night salivary cortisol is a convenient and reliable parameter for the diagnosis of hypercortisolism. Except for ectopic ACTH-production, thresholds considering different indications for evaluation of hypercortisolism were only slightly different. Therefore, they might only be useful if late-night salivary cortisol results near the established cut-off value are present.

Biochemical diagnosis of Cushing's disease: Screening and confirmatory testing

Due to the variable clinical features and its rarity diagnosis of Cushing's disease (CD) is often delayed. Clearly, awareness for CD needs to be raised, accompanied by the availability of simple and accurate screening tests. Late-night salivary cortisol (LNSC), 1 mg dexamethasone suppression test (DST), and urinary free cortisol (UFC) have all been extensively studied, demonstrating high sensitivity and specificity for the diagnosis of Cushing's syndrome. However, each of those well-established tests has its own distinctive features, making it preferable in specific clinical conditions and patient groups. To choose the most appropriate test in individual patients, an expert endocrinologist should be consulted. This review will discuss the pitfalls for each of those tests.

Reference ranges of late-night salivary cortisol and cortisone measured by LC-MS/MS and accuracy for the diagnosis of Cushing's syndrome

PURPOSE

International guidelines recommend salivary cortisol for the diagnosis of Cushing's syndrome. Despite mass spectrometry-based assays are considered the analytical gold-standard, there is still the need to define reference intervals and diagnostic accuracy of such methodology.

METHODS

100 healthy volunteers and 50 consecutive patients were enrolled to compare LC-MS/MS and electrochemiluminescence assay for the determination of late-night salivary cortisol and cortisone. Moreover, we aimed to determine reference intervals of salivary steroids in a population of healthy individuals and diagnostic accuracy in patients with suspected hypercortisolism and in a population including also healthy individuals.

RESULTS

Method comparison highlighted a positive bias (51.8%) of immunoassay over LC-MS/MS. Reference intervals of salivary cortisol (0.17-0.97 µg/L), cortisone (0.84-4.85 µg/L) and ratio (0.08-0.30) were obtained. The most accurate thresholds of salivary cortisol for the diagnosis of hypercortisolism were 1.15 µg/L in the population with suspected hypercortisolism (AUC 1) and 1.30 µg/L in the population including also healthy individuals (AUC 1). Cut-off values of salivary cortisone (7.23 µg/L; Se 92.9%, Sp 97.2%, AUC 0.960 and Se 92.9%, Sp 99.1%, AUC 0.985 in suspected hypercortisolism and in overall population, respectively) and cortisol-to-cortisone ratio (0.20; Se 85.7%, Sp 80.6%, AUC 0.820 and Se 85.7%, Sp 85.5%, AUC 0.855 in suspected hypercortisolism and in overall population, respectively) were accurate and similar in both populations.

CONCLUSION

LC-MS/MS is the most accurate analytical platform for measuring salivary steroids. Obtained reference intervals are coherent with previously published data and diagnostic accuracy for diagnosis of overt hypercortisolism proved highly satisfactory.

Late-Night Salivary Cortisol in Healthy, Community-Dwelling Asian Indians Assessed by Second-Generation ECLIA

BACKGROUND

Late-night salivary cortisol (LNSC) is used as a screening test for Cushing syndrome (CS), but there is no community-derived normative data for the normal upper limit in the South Asian population. This study aimed to determine the upper limit of normal (97.5th percentile) for LNSC in an Asian Indian population using a commercially available second-generation electrochemiluminiscence immunoassay (ECLIA).

METHODS

LNSC in apparently healthy community-dwelling individuals was assessed by multistage cluster sampling. Healthy individuals age 18 to 60 years from 8 urban and 8 rural clusters of Thiruvananthapuram district were studied. Thirty people from an approximate population of 1000 individuals from each cluster participated in the study. A saliva sample was collected between 11 PM and 12 midnight and analyzed using Roche COBAS-e-411 and ultrasensitive Cortisol II kits the next day.

RESULTS

Cortisol values from 474 salivary samples were available for final analysis after exclusion of improperly collected samples. The 97.5th percentile of the LNSC concentrations was 0.25 μg/dL (6.89 nmol/L) (90% CI, 0.23-0.27 μg/dL; ie, 6.34-7.45 nmol/L). In postmenopausal women, median LNSC was significantly higher but the 90% CI for the upper limit of their LNSC (0.28μg/dL or 7.72 nmol/L) overlapped with that of premenopausal women.

CONCLUSIONS

This study establishes the normal value of LNSC estimated by second-generation ECLIA in healthy community-dwelling Asian Indian individuals for the first time. Salivary cortisol at 11 pm to 12 am is less than 0.25μg/dL (6.89 nmol/L) in the general Asian Indian population. Menopause causes a significant increase in LNSC and may lead to overdiagnosis of CS if not interpreted carefully.

Accuracy of Laboratory Tests for the Diagnosis of Cushing Syndrome

CONTEXT

The diagnosis of Cushing syndrome (CS) can be challenging. It remains to be determined which diagnostic tests are the most accurate.

OBJECTIVE

To summarize the accuracy of diagnostic tests for CS using contemporary meta-analytic techniques (hierarchical models).

DATA SOURCES

PubMed, Embase, Scopus, Web of Science, and the Cochrane Database of Systemic Reviews (inception until August 3, 2018).

STUDY SELECTION

Studies performed in adults that determined the accuracy of one or more diagnostic tests: overnight 1-mg dexamethasone suppression test (DST), 2-day low-dose DST (2d DST), 24-hour urinary free cortisol (UFC), late-night salivary cortisol (LNSC), midnight serum cortisol (MSC), and the dexamethasone-suppressed CRH (dex-CRH) and desmopressin (dex-DDAVP) tests.

DATA EXTRACTION

Two authors independently extracted data and performed methodological assessments.

DATA SYNTHESIS

One hundred thirty-nine studies (14 140 participants) were included in the analysis. The respective sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio (95% confidence interval [CI]) estimates include the following: DST 98.6% (96.9%-99.4%), 90.6% (86.4%-93.6%), 10.5 (7.2-15.3), and 0.016 (0.007-0.035); 2d DST 95.3% (91.3%-97.5%), 92.8% (85.7%-96.5%), 13.2 (6.47-27.1), and 0.051 (0.027-0.095); UFC 94.0% (91.6%-95.7%), 93.0% (89.0%-95.5%), 13.3 (8.47-21.0), and 0.065 (0.046-0.092); LNSC 95.8% (93.%-97.2%), 93.4% (90.7%-95.4%), 14.6 (10.3-20.7), and 0.045 (0.030-0.066); MSC 96.1% (93.5%-97.6%), 93.2% (88.1%-96.3%), 14.2 (7.96-25.2), and 0.042 (0.026-0.069); and dex-CRH 98.6% (90.4%-99.8%), 85.9% (67.6%-94.7%), 7.0 (2.80-17.6), and 0.016 (0.002-0.118). A single study evaluated dex-DDAVP. Meta-regression and a novel network meta-analytic approach suggest that DST is the most sensitive while UFC is the least sensitive.

CONCLUSIONS

All of the included diagnostic tests for CS are highly sensitive and specific. It appears that the DST is the most sensitive while the UFC is less sensitive. The specificity of all first-line tests appears comparable.

Cushing's Disease

In patients with Cushing's disease (CD), prompt diagnosis and treatment are essential for favorable long-term outcomes, although this remains a challenging task. The differential diagnosis of CD is still difficult in some patients, even with an organized stepwise diagnostic approach. Moreover, despite the use of high-resolution magnetic resonance imaging (MRI) combined with advanced fine sequences, some tumors remain invisible. Surgery, using various surgical approaches for safe maximum tumor removal, still remains the first-line treatment for most patients with CD. Persistent or recurrent CD after unsuccessful surgery requires further treatment, including repeat surgery, medical therapy, radiotherapy, or sometimes, bilateral adrenalectomy. These treatments have their own advantages and disadvantages. However, the most important thing is that this complex disease should be managed by a multidisciplinary team with collaborating experts. In addition, a personalized and individual-based approach is paramount to achieve high success rates while minimizing the occurrence of adverse events and improving the patients' quality of life. Finally, the recent new insights into the pathophysiology of CD at the molecular level are highly anticipated to lead to the introduction of more accurate diagnostic tests and efficacious therapies for this devastating disease in the near future.