Giorgia Antonelli

Cortisol assays and diagnostic laboratory procedures in human biological fluids

The overview of cortisol physiology, action and pathology is achieved in relation to the hypothalamic-pituitary-adrenal axis alteration by laboratory investigation. The measurements of cortisol and related compound levels in blood, urine and saliva used to study the physiological and pathological cortisol involvement, are critically reviewed. The immunoassay and chromatographic methods for cortisol measurement in the various biological fluids are examined in relation to their analytical performances, reference ranges and diagnostic specificity and sensitivity. Moreover, blood, urine and saliva cortisol level measurements are described taking into account the diagnostic implications. The deduction is that each method requires the definition of its own reference range and its related diagnostic cut-off levels. Thus, this review, stressing the analysis procedures, could help to understand and compare the results of the different assays.

Salivary cortisol and cortisone by LC-MS/MS: validation, reference intervals and diagnostic accuracy in Cushing's syndrome.

BACKGROUND The Endocrine Society recommends late-night salivary cortisol (LNS-F) as a first-line screening test for Cushings syndrome (CS). In the parotid gland, 11β-hydroxysteroid dehydrogenase type 2 inactivates cortisol (F) to cortisone (E), a known source of interference in the more frequently used immunoassays. A highly specific method is mandatory in determining salivary F and E: it is widely accepted that liquid chromatography-tandem mass spectrometry (LC-MS/MS) is the best available technique for this purpose. METHODS A LC-MS/MS method with SPE of saliva samples was developed and validated. Appropriate awakening and bedtime reference ranges were established. The diagnostic performance for F, E and the ratio at bedtime was evaluated in 25 cases of CS. RESULTS The method was linear, with up to 55.4 nmol/L and 51.0 nmol/L, LLOQ of 0.51 nmol/L and 0.55 nmol/L, for F and E, respectively. Within-run and between-run imprecisions were <10% for both analytes. No ion suppression was observed. A cut-off of 2.4 nmol/L for LNS-F yielded a sensitivity of 100% and a specificity of 98% in the diagnosis of CS. CONCLUSIONS The analytical performance of this method justifies its introduction into clinical practice, thus allowing clinicians the opportunity to further investigate CS and other endocrine diseases.

Screening Tests for Cushing's Syndrome: Urinary Free Cortisol Role Measured by LC-MS/MS

INTRODUCTION AND AIM As initial screening for Cushings syndrome (CS), The Endocrine Society guidelines recommend one of the following: the 1-mg dexamethasone suppression test (DST) or late-night salivary cortisol (LNSC) or urinary free cortisol (UFC) measurement. We examined the diagnostic performance of the above-mentioned tests in a series of patients. MATERIALS AND METHODS We retrospectively analyzed 137 patients with clinical conditions suggestive of hypercortisolism: 38 with confirmed CS diagnosis and 99 without (termed non-CS). UFC was measured by liquid chromatography tandem-mass spectrometry, whereas LNSC by the radioimmunometric method and serum cortisol were measured by a chemiluminescence immunoassay. RESULTS Comparing CS vs non-CS, a cutoff of 138 nmol/L after 1-mg DST revealed the best specificity (SP; 97%), whereas the 50-nmol/L cutoff confirmed the best sensitivity (SE; 100%); the SE and SP for LNSC greater than 14.46 nmol/L were, respectively, 84% and 89%, whereas the SE and SP for UFC greater than 170 nmol per 24 hours, they were 97% and 91%. Overall, UFC revealed both a combined higher positive and a lower negative likelihood ratio among first-line tests (respectively 10.7 and 0.03). Computing a receiver-operating curve -contrast analysis to compare the power of each single test with that of the others, alone or combined (DST+LNSC, DST+UFC, and LNSC+UFC) or with that of all the tests together (DST+LNSC+UFC), the UFC assay was at least as good as all the other possible combinations. CONCLUSIONS Measuring UFC by liquid chromatography tandem-mass spectrometry achieves the best accuracy in diagnosing CS among patients presenting with suspected hypercortisolism.

Immunosuppressant therapeutic drug monitoring by LC-MS/MS: Workflow optimization through automated processing of whole blood samples☆

OBJECTIVES Although, due to its high specificity and sensitivity, LC-MS/MS is an efficient technique for the routine determination of immunosuppressants in whole blood, it involves time-consuming manual sample preparation. The aim of the present study was therefore to develop an automated sample-preparation protocol for the quantification of sirolimus, everolimus and tacrolimus by LC-MS/MS using a liquid handling platform. METHODS Six-level commercially available blood calibrators were used for assay development, while four quality control materials and three blood samples from patients under immunosuppressant treatment were employed for the evaluation of imprecision. Barcode reading, sample re-suspension, transfer of whole blood samples into 96-well plates, addition of internal standard solution, mixing, and protein precipitation were performed with a liquid handling platform. After plate filtration, the deproteinised supernatants were submitted for SPE on-line. The only manual steps in the entire process were de-capping of the tubes, and transfer of the well plates to the HPLC autosampler. RESULTS Calibration curves were linear throughout the selected ranges. The imprecision and accuracy data for all analytes were highly satisfactory. The agreement between the results obtained with manual and those obtained with automated sample preparation was optimal (n=390, r=0.96). In daily routine (100 patient samples) the typical overall total turnaround time was less than 6h. CONCLUSIONS Our findings indicate that the proposed analytical system is suitable for routine analysis, since it is straightforward and precise. Furthermore, it incurs less manual workload and less risk of error in the quantification of whole blood immunosuppressant concentrations than conventional methods.

Human saliva cortisone and cortisol simultaneous analysis using reverse phase HPLC technique

BACKGROUND Hyper-hypo tension (like Cushings syndrome, apparent mineralocorticoid excess syndrome and Addisons disease) diagnostic laboratory requires cortisol (F) analysis. The simultaneous analysis of human saliva F and cortisone (E), the inactive F metabolite, by solid phase extraction and RP-HPLC was studied. METHODS Saliva/standard samples were C18-SPE extracted, dried and resuspended. E and F were analysed by isocratic RP-HPLC (acetonitrile/water 27/73%) and UV detection. In the morning and in the evening Salivette stimulated saliva specimens were collected from healthy volunteers. RESULTS The E and F calibration curve ranges were 11.0-110.0 and 5.5-55.0 nmol/l respectively. The LOD was 0.2 and 0.1 nmol/l for E and F respectively. The intra and inter assay CVs were respectively 2.7-6.6 and 5.6-7.0% for E and 5.8-7.0 and 11.7-13.1% for F. The E and F spiked saliva sample recovery was 99% and 88% respectively. Saliva specimen stability was validated. E and F saliva levels in healthy volunteers were significantly (p<0.001) higher at 8 a.m. compared with 11 p.m. (26.4+/-8.9 vs. 4.3+/-2.9 nmol/l for E; 11.1+/-4.0 vs. 2.5+/-1.5 nmol/l for F, respectively). CONCLUSIONS This method is suitable for periodic analyses in a clinical biochemistry laboratory for endocrinology investigation purposes, simultaneously analysing E and F levels in a saliva specimen.

IGF-I/IGFBP system: metabolism outline and physical exercise.

The GH/IGF-I system plays a well-known hormonal role and its effects, mainly anabolic and insulin-sensitizing, are mediated through endocrine as well as paracrine/autocrine mechanisms. This system includes the binding proteins, namely GH binding proteins and IGF-I binding proteins (IGFBP). As expected, this axis plays a key role in organism modification in consequence of a physical exercise. Physical activity, training, and exercise capacity chiefly involve anabolism process modifications of various tissues, in particular muscular adjustments. Numerous investigators found a correlation among the level of exercise tolerance, muscle strength or walking speed and IGF-I/IGFBP-3 concentrations. However, also inverse and absent correlations between circulating IGF-I concentrations and acute or chronic exercise responses have been reported. IGF-I is generally accepted as an important GH mediator with metabolic effects, through both endocrine and paracrine or autocrine mechanisms. GH is the main regulator of the hepatic synthesis of IGF-I and IGFBP-3, which is the most abundant IGF carrier in human plasma. Recently, it has been shown that the physical exercise stimulatory impact on skeletal muscles is mediated through an increased local IGF-I synthesis with an IGFPB involvement. An absent association of exercise performance and circulating IGF-I may indicate that exercise will exert muscle strength by predominately locally derived paracrine or autocrine mediators rather than endocrine circulating IGF-I. The present review considers the general aspects of the IGF/IGFPB system and the role of the IGF/IGFPB system in relation to physical exercise (type, duration, etc.) taking into account the training aspects.

The diagnostic performance of urinary free cortisol is better than the cortisol/cortisone ratio in detecting de novo Cushing's syndrome: the use of a LC-MS/MS method in routine clinical practice.

OBJECTIVE The Endocrine Society Clinical Guidelines recommend measuring 24-h urinary free cortisol (UFF) levels using a highly accurate method as one of the first-line screening tests for the diagnosis of Cushings Syndrome (CS). We evaluated the performance of UFF, urinary free cortisone (UFE), and the UFF:UFE ratio, measured using a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. SUBJECTS AND METHODS The LC-MS/MS was used to analyze UFF and UFE levels in 43 surgically confirmed CS patients: 26 with Cushings disease (CD, 16 de novo and ten recurrences), 11 with adrenal CS and six with ectopic CS; 22 CD patients in remission; 14 eu-cortisolemic CD patients receiving medical therapy; 60 non-CS patients; and 70 healthy controls. Sensitivity and specificity were determined in the combined groups of non-CS patients, healthy controls, and CD in remission. RESULTS UFF>170 nmol/24 h showed 98.7% specificity and 100% sensitivity for de novo CS, while sensitivity was 80% for recurrent CD patients, who were characterized by lower UFF levels. The UFF:UFE and UFF+UFE showed lower sensitivity and specificity than UFF. Ectopic CS patients had the highest UFF and UFF:UFE levels, which were normal in the CD remission patients and in those receiving medical therapy. CONCLUSIONS Our data suggest high diagnostic performance of UFF excretion measured using LC-MS/MS, in detecting de novo CS. UFF:UFE and UFF+UFE assessments are not useful in the first step of CS diagnosis, although high levels were found to be indicative of ectopic CS.

Cortisol and cortisone ratio in urine: LC-MS/MS method validation and preliminary clinical application

Abstract Background: The determination of urinary cortisol/cortisone ratio is of clinical utility in cases of Cushing’s syndrome, apparent mineralocorticoid excess, and also provides information on 11β-hydroxysteroid dehydrogenase (11β-HSD) type 2 activity. It is therefore of utmost importance to ensure accurate cortisol and cortisone measurement and establish appropriate reference ranges. Methods: After the isotopic dilution of urine, sample cleanups were obtained with on-line solid-phase extraction and cortisol and cortisone, separated using a Zorbax Eclipse XDB-C18 HPLC analytical column, were analyzed by tandem mass spectrometry with an electrospray ionization source in positive ion mode operation. Results: The method was linear, with concentrations of up to 625 and 1125 nmol/L and lower limit of quantitation (LLOQ) of 5 and 6 nmol/L, for cortisol and cortisone, respectively. Within-run and between-run coefficients of variation were <5% and 6% for cortisol and 6% and 8% for cortisone, respectively. No ion suppression was observed. The non-parametric reference range for the cortisol/cortisone ratio was 0.14–1.09. Conclusions: A simple and sensitive liquid chromatography tandem mass spectrometry method was developed and validated for the measurement of cortisol and cortisone in urine. Our findings indicate that the proposed analytical method is suitable for routine purposes and useful in many pathological conditions.

An approach for estimating measurement uncertainty in medical laboratories using data from long-term quality control and external quality assessment schemes

Abstract Background: The present study was prompted by the ISO 15189 requirements that medical laboratories should estimate measurement uncertainty (MU). Methods: The method used to estimate MU included the: a) identification of quantitative tests, b) classification of tests in relation to their clinical purpose, and c) identification of criteria to estimate the different MU components. Imprecision was estimated using long-term internal quality control (IQC) results of the year 2016, while external quality assessment schemes (EQAs) results obtained in the period 2015–2016 were used to estimate bias and bias uncertainty. Results: A total of 263 measurement procedures (MPs) were analyzed. On the basis of test purpose, in 51 MPs imprecision only was used to estimate MU; in the remaining MPs, the bias component was not estimable for 22 MPs because EQAs results did not provide reliable statistics. For a total of 28 MPs, two or more MU values were calculated on the basis of analyte concentration levels. Overall, results showed that uncertainty of bias is a minor factor contributing to MU, the bias component being the most relevant contributor to all the studied sample matrices. Conclusions: The model chosen for MU estimation allowed us to derive a standardized approach for bias calculation, with respect to the fitness-for-purpose of test results. Measurement uncertainty estimation could readily be implemented in medical laboratories as a useful tool in monitoring the analytical quality of test results since they are calculated using a combination of both the long-term imprecision IQC results and bias, on the basis of EQAs results.

Salivary free Insulin-like Growth Factor-I levels: Effects of an acute physical exercise in athletes

Background/aims: The offer of human saliva IGF-I (sIGF-I) measurement in athletes investigation is a new proposal. The aim was to investigate the physical exercise effect on sIGF-I and explore plasma free IGF-I relation. Materials and methods: Saliva and blood were collected from well-trained athletes, investigated immediately before and at the end of a physical exercise test. Results: sIGF-I was significantly increased at the end of the physical exercise. The plasma free IGF-I concentrations did not demonstrate any difference. The saliva total protein level (sTP) was also significantly increased. A positive correlation between sTP and sIGF-I, was observed, both before and after physical exercise, and between salivary and plasma free IGF-I only after physical exercise. The salivary free IGF-I level significantly increased after physical exercise, moreover a correlation with the plasma levels exists in post-exercise condition. Conclusion: The physical exercise affects sIGF-I as well as the sTP. The correlation between plasma and salivary free IGF-I levels only in post-exercise condition suggests further studies to investigate the effects of different type and duration of physical exercise. The comparison with other salivary biochemical parameter investigation would also further increase comprehension on the role of salivary IGF-I.