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

Abstract

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.

Late‐night salivary cortisol cut‐offs for diagnosis of Cushing syndrome using second‐generation electrochemiluminescence immunoassay kits

“…18,20 We employed a ROC analysis to derive the optimal LNSC cut-off with highest sensitivity and specificity, an approach most consistently used in the literature. 19,[21][22][23][24][25][26][27][28][29][30][31][32] Our ROC-derived LNSC cut-off was also very close to the 95th percentile determined in healthy population by the manufacturer, that is, 7.56 nmol/L 8 and the 97.5th percentile determined in healthy community-dwelling Asian Indians by Prasad et al 35 with the same assay, that is, 6.89 nmol/L. Furthermore, we found that an alternative approach of using 95th percentile of LNSC (6.76 nmol/L) in our controls as the cut-off yielded a similarly high sensitivity (98%) and specificity (96%).…”

“…Since salivary cortisol measurements were not found to be affected by age (in adults <65 years of age) in a recent study by Raff et al, 39 we do not expect a significant implication of this difference for our study findings. Third, we used serum separator tubes (which are routinely available in our hospital) to collect saliva samples rather than the more commonly used plain polypropylene tubes 17,35 . However, the approach was similar in both cases and controls; whether this nonconventional approach affects concentration of cortisol in saliva samples needs a formal evaluation.…”

Long‐acting porcine ACTH stimulated salivary cortisol in the diagnosis of adrenal insufficiency

“…3 Late night salivary cortisol is one of the preferred screening tests for Cushing Syndrome with well-defined cut-off values. 2,4 Salivary cortisol performs better than plasma cortisol in conditions with altered cortisol-binding globulin (CBG) levels like contraceptive use, pregnancy and liver cirrhosis. [5][6][7] In spite of the advantages, the role of salivary cortisol in the diagnosis of adrenal insufficiency (AI) is not well established.…”

“…Moreover, it is stable at room temperature for up to 5 days thus facilitating storage and transportation 3 . Late night salivary cortisol is one of the preferred screening tests for Cushing Syndrome with well‐defined cut‐off values 2,4 . Salivary cortisol performs better than plasma cortisol in conditions with altered cortisol‐binding globulin (CBG) levels like contraceptive use, pregnancy and liver cirrhosis 5–7 .…”

Eclia Test- Review

“…Electro chemiluminescence immuno assay is a new developing method to determine antibodies in human being's blood sample.this has evolved from various other immunoassay methods that were previously used for detection of enzyme/antibody etc 5 Determination of antibody is done by chemical reactivity with materials like ruthenium, osmium etc., that are coated on monoclonal antibodies and on reaction produce luminescent molecules hence the name. This production of luminescent molecules makes determination uncomplicated 6 .…”