Stability of plasma adrenocorticotrophic hormone (ACTH): Influence of hemolysis, rapid chilling, time, and the addition of a maleimide

Pitfalls in the Diagnosis and Management of Hypercortisolism (Cushing Syndrome) in Humans; A Review of the Laboratory Medicine Perspective

Biochemical confirmation of a diagnosis of hypercortisolism (Cushing syndrome) is vital to direct further investigations, especially given the overlap with non-autonomous conditions, such as pseudo-Cushing, and the morbidity associated with missed diagnoses. A limited narrative review was performed focusing on the laboratory perspective of the pitfalls of making a biochemical diagnosis of hypercortisolism in those presenting with presumed Cushing syndrome. Although analytically less specific, immunoassays remain cheap, quick, and reliable in most situations. Understanding cortisol metabolism can help with patient preparation, specimen selection (e.g., consideration of urine or saliva for those with possible elevations of cortisol binding globulin concentration), and method selection (e.g., mass spectrometry if there is a high risk of abnormal metabolites). Although more specific methods may be less sensitive, this can be managed. The reduction in cost and increasing ease of use makes techniques such as urine steroid profiles and salivary cortisone of interest in future pathway development. In conclusion, the limitations of current assays, particularly if well understood, do not impede diagnosis in most cases. However, in complex or borderline cases, there are other techniques to consider to aid in the confirmation of hypercortisolism.

Instability of corticotropin during long-term storage - myth or reality?

OBJECTIVES

Corticotropin is notorious for its instability. Whereas several studies have investigated its short-term stability in plasma following venous blood sampling, studies on long-term stability are lacking. Here we investigated the long-term storage stability of corticotropin in ethylenediaminetetraacetic acid containing plasma.

METHODS

Specimens from healthy volunteers (neat, spiked) were stored in polypropylene microcentrifuge tubes with socket screw-caps at -20 °C and -70 °C for up to one and a half years. Corticotropin in plasma was measured using an Abbott research only immunoassay. Separately, specimens from patients were collected during diagnostic routine testing and stored in polystyrene tubes with push-caps at -20 °C for up to 6 years. In these samples corticotropin hormone was measured using the Diasorin corticotropin immunoassay.

RESULTS

Storage of specimens at -20 °C or -70 °C for up to one and a half years showed minimal changes (<11%) in corticotropin levels, while storage of patient samples at -20 °C for up to 6 years showed a significant (54%) reduction in corticotropin levels.

CONCLUSIONS

Corticotropin levels are stable in plasma when stored at -20 °C for one and a half years using the Abbott research only assay, but with longer storage time a significant reduction in corticotropin levels can be expected. Once specimens are stored for future corticotropin measurements, one should consider storage time, storage temperature and assay differences.

A Pitfall of Falsely Elevated ACTH: A Case Report and Literature Review

A 35-year-old woman with unintentional weight gain, hyperpigmentation of bilateral palms, and general fatigue was initially suspected of Cushing’s syndrome or adrenal insufficiency based on the isolated elevation of the plasma adrenocorticotropic hormone (ACTH) level (113.0 pg/mL) in the Siemens ACTH Immulite assay (ACTH [Immulite]). However, both of the diagnoses were excluded by screening tests including the overnight dexamethasone suppression test, the 24-hour urinary free cortisol excretion, and the ACTH stimulation test in spite of the consistent elevation of the plasma ACTH levels. We speculated that the existence of the immunoassay interference may be the underlying cause because the plasma ACTH level analyzed by the CIS Bio International ELSA-ACTH immunoassay (ELSA-ACTH) was within the normal range. After reviewing our case and several reported cases of falsely elevated plasma ACTH levels, we conclude that when discrepancy between clinical symptoms and laboratory measurements exists, medical practitioners ought to rely on formal diagnostic criteria rather than misleading laboratory results to avoid misdiagnosis or even unnecessary invasive testing and procedures. In addition, current methods for investigation and elimination of immunoassay interferences should be applied with caution due to variable efficacy and inevitable deviations.

Evaluation of plasma ACTH stability using the Roche Elecsys immunoassay

BACKGROUND

Adrenocorticotropic hormone (ACTH) has been reported to be labile in blood due to proteolytic degradation and stringent procedures are followed to prevent in vitro degradation after sample collection.

OBJECTIVE

The purpose of this study was to examine the effect of time and temperature before and after separation of plasma from cells in the quantitation of plasma ACTH.

METHODS

Our current protocol includes sample collection in a pre-chilled tube, transport on ice and immediate centrifugation at 4 °C. These reference conditions were compared against sample processing in tubes and centrifuge set at room-temperature; using delayed centrifugation at 4 °C. ACTH stability was evaluated at ambient and refrigerated temperatures after collection and plasma separation using the reference protocol. Plasma samples were analyzed using the Roche Elecsys ACTH immunoassay.

RESULTS

Quantification of ACTH was not impacted by the use of non-chilled tubes and centrifuge and up to a 4 h delay in separation of plasma from cells. Average percent differences in plasma ACTH concentration from time 0 was <10% up to 12 h at ambient temperature. Refrigeration of plasma did not preserve ACTH stability at 12 h and longer storage resulted in significant ACTH degradation at both ambient and refrigerated temperatures.

CONCLUSIONS

As supported by these data, previously recommended strict specimen collection and processing requirements are not necessary for measuring ACTH with the Roche Elecsys immunoassay.

Stress hypothesis overload: 131 hypotheses exploring the role of stress in tradeoffs, transitions, and health

Stress is ubiquitous and thus, not surprisingly, many hypotheses and models have been created to better study the role stress plays in life. Stress spans fields and is found in the literature of biology, psychology, psychophysiology, sociology, economics, and medicine, just to name a few. Stress, and the hypothalamic-pituitaryadrenal/interrenal (HPA/I) axis and sympathetic nervous system (SNS), are involved in a multitude of behaviors and physiological processes, including life-history and ecological tradeoffs, developmental transitions, health, and survival. The goal of this review is to highlight and summarize the large number of available hypotheses and models, to aid in comparative and interdisciplinary thinking, and to increase reproducibility by a) discouraging hypothesizing after results are known (HARKing) and b) encouraging a priori hypothesis testing. For this review I collected 214 published hypotheses or models dealing broadly with stress. In the main paper, I summarized and categorized 131 of those hypotheses and models which made direct connections among stress and/or HPA/I and SNS, tradeoffs, transitions, and health. Of those 131, the majority made predictions about reproduction (n = 43), the transition from health to disease (n = 38), development (n = 23), and stress coping (n = 18). Additional hypotheses were classified as stage-spanning or models (n = 37). The additional 83 hypotheses found during searches were tangentially related, or pertained to immune function or oxidative stress, and these are listed separately. Many of the hypotheses share underlying rationale and suggest similar, if not identical, predictions, and are thus not mutually exclusive; some hypotheses spanned classification categories. Some of the hypotheses have been tested multiple times, whereas others have only been examined a few times. It is the hope that multi-disciplinary stress researchers will begin to harmonize their naming of hypotheses in the literature so as to build a clearer picture of how stress impacts various outcomes across fields. The paper concludes with some considerations and recommendations for robust testing of stress hypotheses.

Salivary cortisone, as a biomarker for psychosocial stress, is associated with state anxiety and heart rate

BACKGROUND

Stress activates the central nervous, the autonomic nervous, and the endocrine system. This study aimed to (1) test the usability of salivary cortisone in a standardized psychosocial stressor, (2) create a comprehensive profile of hormonal responses to determine laboratory parameters with high discriminatory power, and (3) analyze their association with psychometric and autonomic stress measures.

METHODS

Healthy young men (18-35 years) completed either the Trier Social Stress Test (TSST) (n = 33) or a Placebo-TSST (n = 34). Blood and saliva were collected at 14 time points along with state-anxiety (STAI) and heart rate. Serum steroids (cortisol*, cortisone*, dehydroepiandrosterone-sulfate, androstenedione*, progesterone*, 17-hydroxyprogesterone*, testosterone, estradiol*, aldosterone*), salivary cortisol* and cortisone*, copeptin*, adrenocorticoptropic hormone*, corticosteroid-binding globulin, and salivary alpha-amylase* were analyzed. We used mixed-design ANOVAs to test group differences, receiver operator characteristic (ROC) curve analyses to assess the discriminatory power of each measure, and Spearman correlation analyses to probe the association between measures.

RESULTS

The largest area under the ROC curve was observed in salivary cortisone at 20 min after the end of the TSST (AUC = 0.909 ± 0.044, p < 0.0001). Significant time-by-group interactions were found in the parameters marked with * above, indicating stress-induced increases. The peak response of salivary cortisone was significantly associated with those of STAI (rho = 0.477, p = 0.016) and heart rate (rho = 0.699, p < 0.0001) in the TSST group.

CONCLUSION

Our study found salivary cortisone to be a stress biomarker with high discriminatory power and significant correlations with subjective and autonomic stress measures. Our results can inform future stress studies of sampling time for different laboratory parameters.

Current laboratory requirements for adrenocorticotropic hormone and renin/aldosterone sample handling are unnecessarily restrictive

Samples for adrenocorticotropic hormone (ACTH) and aldosterone/renin analysis usually require rapid transport to the receiving laboratory for immediate separation and freezing. In practice, this means assessment is limited to hospital settings and many samples are rejected. We examined whether these requirements are necessary by assessing the stability of ACTH, aldosterone and renin over 48 hours in whole blood collected in serum gel and EDTA plasma from 31 participants. Our results show that ACTH collected into EDTA plasma is stable at room temperature for at least 6 hours, mean change at 6 hours -2.6% (95% CI -9.7 to 4.5). Both aldosterone and renin were stable collected on serum gel at room temperature for at least 6 hours: mean change aldosterone +0.2% (95% CI -3.6 to 4.0), renin -1.9% (95% CI -7.0 to3.2). Therefore, by using appropriate preservatives, ACTH and aldosterone/renin can be measured on samples collected at room temperature and processed within 6 hours. This would facilitate outpatient and emergency room assessment of these analytes.

Preanalytical stability of adrenocorticotropic hormone depends on both time to centrifugation and temperature

OBJECTIVE

The purpose of our study was to analyze the effects of temperature, time delay, and time to centrifugation on the stability of human plasma adrenocorticotropin (ACTH) measurements.

METHODS

Twenty-one EDTA whole blood sample pools were centrifuged at 1100 ×g for 10 minutes at 4°C either immediately or after storage for 2, 4, 8, and 24 hours at 4°C or room temperature. Plasma ACTH was then measured either immediately or after 2, 4, 8, and 24 hours storage at 4°C or room temperature.

RESULTS

The change in ACTH concentrations was affected significantly (from 8.1±5.0% to 12.4±2.9% at 4 hours, P<.005) by time to centrifugation at room temperature. However, it remained stable (<5% change) up to 8 hours at 4°C in samples both centrifuged immediately and uncentrifuged.

CONCLUSIONS

To get accurate values of plasma ACTH concentrations, if the samples cannot be transferred to the laboratory for analysis at room temperature within 2 hours, they should be immediately stored at 4°C, and analyzed within 8 hours.

Whole blood samples for adrenocorticotrophic hormone measurement can be stored at room temperature for 4 hours

INTRODUCTION

The aim of this study was to investigate and compare the stability of adrenocorticotrophic hormone (ACTH) in whole blood stored on ice and at room temperature for up to 48 hours. This study differs from previous studies by a larger data material.

MATERIALS AND METHODS

EDTA-blood samples from 30 patients were collected, aliquoted and stored on ice or at room temperature for 0, 2, 4, 24, or 48 h before centrifugation, and the plasma was stored frozen until analysis. All samples were analyzed using an automated electrochemiluminescence immunoassay on cobas 6000 e601. The change in ACTH concentration was illustrated as ACTH recovery compared to standard conditions defined as samples stored immediately on ice, centrifuged and plasma frozen within 1 h. A change in ACTH concentration of more than 10% was considered to be of clinical relevance.

RESULTS

The results showed no clinically relevant change in ACTH recovery for up to 4 h compared to standard conditions. For samples stored at room temperature for 4 h, a significant (p < .0001) relative mean change in ACTH concentrations of -4.3% was observed.

CONCLUSION

The comparison between samples stored at room temperature for up to 4 h and standard conditions showed that ACTH samples do not require cooling until centrifugation, if a mean difference in ACTH concentration of -4.3%, between the individual results, can be accepted.

The effects of sample handling and N-phenylmaleimide on concentration of adrenocorticotrophic hormone in equine plasma

REASONS FOR PERFORMING STUDY

Previous reports suggest that adrenocorticotrophic hormone (ACTH) degrades rapidly, limiting its use as a diagnostic test.

OBJECTIVES

This study quantified effects of processing delays on ACTH concentrations and investigated the addition of N-phenylmaleimide (maleimide), a protease inhibitor, as a means of reducing ACTH degradation.

STUDY DESIGN

Experimental study.

METHODS

Venous blood was collected from 8 healthy horses and 8 horses with pituitary pars intermedia dysfunction (PPID) with a range of ACTH concentrations. Baseline ACTH concentrations were established immediately using a chemiluminescent assay. Plasma samples were then: 1) centrifuged immediately, 2) centrifuged immediately with the addition of maleimide, or 3) allowed to separate by gravity followed by the addition of maleimide, before all samples were stored at 22°C and analysed at 4, 8, 24 and 48 h post collection. A linear mixed effects model and Bland-Altman analyses were performed. Significance was set at P < 0.05.

RESULTS

No significant effect of plasma treatment (P = 0.1) on change in ACTH concentration was identified. However, significant effects of horse health status (P < 0.001) and time (P < 0.001) on change in ACTH concentration were identified. No significant interactions were found. Significant decreases in ACTH concentration occurred in horses with PPID between 4 and 8 h after blood collection. In non-PPID horses, the decrease in ACTH concentration over time was not significant. Agreement with baseline values decreased over time and was greater for non-PPID horses than for PPID horses.

CONCLUSIONS

Clinically useful results are still obtained if ACTH concentration is measured up to 48 h after sample collection. Allowing samples to separate by gravity rather than centrifugation did not have a significant effect on ACTH concentration, and the addition of maleimide was of no benefit.

Interpretation of hormone levels in older patients: points for consideration

Blood hormone and tumor marker concentrations are usually determined by immunochemical methods which are based on an unique reaction between antigen and assay capture antibody. Despite the speed and simplicity of assays performance on automatic immunochemistry platforms, the interpretation of final results requires a deep knowledge of method fallibility. General lack of immunoassays standardization, presence of cross-reacting substances in patient's sample, limitation of free hormones measurement due to abnormal analyte binding protein concentrations, assay interferences due to patient's autoantibodies, and heterophilic antibodies, as well as proper interpretation of very low- and very high-sample analyte levels, are the main points discussed in respect to hormones and tumor markers measurement in geriatric population.