A survey of endocrine function testing by clinical biochemistry laboratories in the UK

Hidradenitis suppurativa: Disease pathophysiology and sex hormones

Hidradenitis suppurativa is a cutaneous chronic inflammatory disease that is estimated to affect about 1% of the population and caused pain, malodorous discharge, disfigurement, and poor quality of life with psychosocial problems. The typical features are recurrent painful nodules, abscesses, and sinus tracts on the axillae, groins, gluteal areas, and anogenital regions since postpuberty. Smoking and obesity are two major triggering factors of hidradenitis suppurativa. Women are prone to have hidradenitis suppurativa than men in Western countries, but the male-to-female ratio is reversed in oriental countries. The disease severity can be affected by menstruation, pregnancy, and menopause. Furthermore, the phenotypes are different among men and women with hidradenitis suppurativa. Men are prone to have buttock involvement while women are prone to have axillary, groins, and submammary lesions. This review introduces the skin appendages and pathophysiology of hidradenitis suppurativa and then focuses on the sex difference and the effects of sex hormones on hidradenitis suppurativa and current hormone-associated treatments.

Do we need 30 min cortisol measurement in the short synacthen test: a retrospective study

OBJECTIVE

The short synacthen test (SST) is widely used across the UK to assess adrenal reserve but there remains no consensus on the timing of cortisol sampling to help diagnose adrenal insufficiency. The main objective of our study was to see if both 30 and 60 min sample are required following administration of synacthen to investigate suspected adrenal insufficiency (AI).

DESIGN

This was a single-centre retrospective study of 393 SSTs measuring 0, 30 and 60 min cortisol levels after administration of 250 µg of synacthen.

PATIENTS AND METHODS

All the SSTs for patients suspected of primary or secondary AI between April 2016 and October 2018 were included in this study. The tests were performed as per our hospital protocol. A post-adrenocorticotropic hormone (ACTH) cortisol response of 420 nmol/L at any time point was considered adequate to rule out AI. The data were analysed to ascertain the proportion of patients who achieved this level at 30 and/or 60 min.

RESULTS

A total of 393 SST results were included in this study. Patients were divided into two groups depending on whether (group A) or not (group B) they were on steroids. Overall, a total of 313 (79.6%) subjects achieved cortisol level of ≥420 nmol/L at 30 and 60 min while 19 (4.8%) had late response (ie, insufficient 30 min cortisol levels, rising to ≥420 nmol/L at 60 min). Another 61 subjects (15.5%) showed insufficient response at both 30 and 60 min (ie, failed to achieved level of ≥420 nmol/L). Importantly, there was no patient in either group who had adequate response at 30 min and then failed at 60 min. Patients in group A were more likely to have inadequate response at both 30 and 60 min while patients in group B were more likely to have normal response at both time points.

CONCLUSIONS

Our results suggest that about 5% of people undergoing SST may be inappropriately diagnosed as having AI (and subjected to long-term unnecessary steroid treatment) if the 60 min sample is not maintained. We suggest that 30 min sample does not add any additional diagnostic utility and can be omitted thus simplifying SST even further and saving on cost and resources. We propose that single measurement after 60 min of administration of synthetic ACTH is a sufficient screening test for AI.

Redefining the perioperative stress response: a narrative review

The systemic stress response triggered by surgical trauma is characterised by sterile inflammation preceding metabolic and neuroendocrine dysregulation. However, the relevance of the classically described 'stress response' is now highly questionable in an era where profound physiological deconditioning is common in older, frail surgical patients. Commonly used assessment techniques do not accurately reflect hypothalamic-pituitary-adrenal axis integrity after major surgery. Clinical interpretation of plasma concentrations of cortisol, the prototypical stress hormone, is rarely accurate, because of study heterogeneity, the inherently dynamic characteristics of cortisol production, and assay variability. Before surgery, chronic psychosocial stress and common cardiorespiratory co-morbidities are clinically relevant modifiers of neuroendocrine activation to acute stress/inflammation. The frequent development of multi-morbidity after major surgery further clouds the compartmentalised, discrete model of neuroendocrine activation after initial tissue injury. Starvation, impaired mobility, and sepsis after surgery generate distinct neuroendocrine profiles that challenge the conventional model of neuroendocrine activation. Basic science studies suggest that high circulating levels of cortisol may directly cause organ injury. Conversely, randomised controlled clinical trials investigating glucocorticoid supplementation have delivered contrasting results, with some suggesting a protective effect in the perioperative period. Here, we consider many of the confounding factors that have emerged to challenge the conventional model of the surgical stress response, and suggest that a more nuanced understanding of changes in hypothalamic-pituitary-adrenal axis physiology is warranted to advance perioperative medicine. Re-examining the perioperative stress response presents opportunities for improving outcomes through enhancing the understanding of the neuroendocrine aspects of preparation for and recovery from surgery.

In primary care, is measuring free-thyroxine plus thyroid-stimulating hormone to detect hypopituitarism cost-effective? A cost utility analysis using Markov chain models

OBJECTIVE

We examined whether it is cost-effective to measure free thyroxine (FT4) in addition to thyrotropin (thyroid-stimulating hormone (TSH)) on all requests for thyroid function tests from primary care on adult patients.

BACKGROUND

Hypopituitarism occurs in about 4 people per 100 000 per year. Loss of thyrotropin (TSH) secretion may lead to secondary hypothyroidism with a low TSH and low FT4, and this pattern may help to diagnose hypopituitarism that might otherwise be missed.

DESIGN

Markov model simulation.

PRIMARY OUTCOME MEASURE

Incremental cost-effectiveness ratio (ICER), the ratio of cost in pounds to benefit in quality-adjusted life years of this strategy.

RESULTS

The ICER for this strategy was £71 437. Factors with a large influence on the ICER were the utilities of the treated hypopituitary state, the likelihood of going to the general practitioner (GP) and of the GP recognising a hypopituitary patient. The ICER would be below £20 000 at a cost to the user of an FT4 measurement of £0.61.

CONCLUSION

With FT4 measurements at their present cost to the user, routine inclusion of FT4 in a thyroid hormone profile is not cost-effective.

Lessons learnt from a case of missed central hypothyroidism

We present the case of a 57-year-old lady who had a delayed diagnosis of central hypothyroidism on a background of Grave's thyrotoxicosis and a partial thyroidectomy. During the twenty years following her partial thyroidectomy, the patient developed a constellation of symptoms and new diagnoses, which were investigated by numerous specialists from various fields, namely rheumatology, renal and respiratory. She developed significantly impaired renal function and raised creatine kinase (CK). She was also referred to a tertiary neurology service for investigation of myositis, which resulted in inconclusive muscle biopsies. Recurrently normal TSH results reassured clinicians that this did not relate to previous thyroid dysfunction. In 2015, she developed increased shortness of breath and was found to have a significant pericardial effusion. The clinical biochemist reviewed this lady's blood results and elected to add on a free T4 (fT4) and free T3 (fT3), which were found to be <0.4 pmol/L (normal range (NR): 12-22 pmol/L) and 0.3 pmol/L (NR: 3.1-6.8 pmol/L), respectively. She was referred urgently to the endocrine services and commenced on Levothyroxine replacement for profound central hypothyroidism. Her other pituitary hormones and MRI were normal. In the following year, her eGFR and CK normalised, and her myositis symptoms, breathlessness and pericardial effusion resolved. One year following initiation of Levothyroxine, her fT4 and fT3 were in the normal range for the first time. This case highlights the pitfalls of relying purely on TSH for excluding hypothyroidism and the devastating effect the delay in diagnosis had upon this patient.

Learning points

Isolated central hypothyroidism is very rare, but should be considered irrespective of previous thyroid disorders.If clinicians have a strong suspicion that a patient may have hypothyroidism despite normal TSH, they should ensure they measure fT3 and fT4.Laboratories that do not perform fT3 and fT4 routinely should review advice sent to requesting clinicians to include a statement explaining that a normal TSH excludes primary but not secondary hypothyroidism.Thyroid function tests should be performed routinely in patients presenting with renal impairment or a raised CK.

Cushing's disease, pseudo-Cushing states and the dexamethasone test: a historical and critical review

The dexamethasone (DXM) test has been widely used for diagnosing Cushing's disease (CD). The purpose of this paper is to review its diagnostic merit based on calculation of data extracted from earlier publications. Studies presenting individual values for patients with CD and normal subjects were identified through PubMed searches and references in pertinent studies. Calculation of the retrieved data demonstrated huge variation in the relative suppressibility, negative suppression being common. Furthermore, in almost each study retrieved, the pre and post DXM values were closely correlated. Finally, the generally accepted view that DXM causes less suppression in Cushing's disease than in euadrenal controls appears unfounded. A central issue in the definition of so-called "pseudo-Cushing's states" is failure to suppress cortisol secretion with DXM. From analysis of the literature it appears quite possible that this does not reflect a specific endocrine deficit, but a physiological "stress" reaction. The above issues question the diagnostic value of the test, in particular in clinically and biochemically borderline cases.

Determining the utility of the 60 min cortisol measurement in the short synacthen test

OBJECTIVE

Despite the widespread use of the short synacthen test (SST), there remains no clear consensus on sampling times for the measurement of serum cortisol that best determines adrenal reserve. We set out to establish whether there is any value in measuring serum cortisol at 60 min following administration of synacthen.

DESIGN

Retrospective data analysis of 500 SST results measuring 0, 30 and 60 min cortisol levels after administration of 250 μg of synacthen at 2 large urban National Health Teaching Hospitals in the UK.

PATIENTS AND MEASUREMENTS

Individuals thought to have primary or secondary adrenal insufficiency given 250 μg of synacthen.

MEASUREMENTS

Serum cortisol levels measured at 0, 30 and 60 min, looking to see how many people who had adrenal insufficiency at the 30 min sample but in whom the 60 min sample showed adequate adrenal reserve.

RESULTS

The results from 384 people were analysed. A total of 276 had normal responses at 30 min and also at 60 min. A sum of 33 individuals had 'insufficient' (i.e., <550 nmol/l) 30 min cortisol levels, rising to ≥ 550 nmol/l at the 60 min test. All 75 individuals who were insufficient at 60 min were also insufficient at 30 min. No individuals passed (≥550 nmol/l) at 30 min and then failed (<550 nmol/l) at 60 min.

CONCLUSIONS

These results suggest that a significant proportion of people undergoing a SST may be inappropriately diagnosed as having adrenal insufficiency if the 60 min sample is not measured. We suggest that the 60 min sample is measured in all individuals having a SST to prevent unnecessary over-diagnosis of adrenal insufficiency.

The diagnosis and investigation of adrenal insufficiency in adults

There is considerable variation in the methods used to diagnose and investigate adrenal insufficiency in clinical practice. These include a range of adrenocorticotropin (ACTH) stimulation and other dynamic testing protocols, serum cortisol cut-off values for diagnosis and tests used for differential diagnosis. With the introduction of modern cortisol and ACTH assays, the interpretation of tests used for diagnosis and differential diagnosis has become more complex and requires local validation. This review examines the basis of normal hypothalamic-pituitary-adrenal axis function and adrenal insufficiency states based upon an evidence base accumulated over the past four decades. The role of the laboratory in the differential diagnosis and interpretation based upon assay methodology is discussed. The accurate identification of patients who may benefit from corticosteroid replacement in special settings such as critical illness is challenging and will be explored.

Evaluation of the hypothalamic-pituitary-adrenal axis function in childhood and adolescence

The hypothalamic-pituitary-adrenal (HPA) axis plays an important role in the maintenance of basal and stress-related homeostasis. The hypothalamus controls the secretion of adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn stimulates the secretion of glucocorticoids from the adrenal cortex. Glucocorticoids, the final effectors of the HPA axis, regulate a broad spectrum of physiologic functions essential for life and exert their effects through their ubiquitously distributed intracellular receptors. Alterations in the activity of the HPA axis may present with symptoms and signs of glucocorticoid deficiency or excess. Detailed endocrinologic evaluation is of primary importance in determining the diagnosis and/or etiology of the underlying condition. We review the most common endocrinologic investigations used in the evaluation of the HPA axis integrity and function.

Measurement of urinary free cortisol by tandem mass spectrometry and comparison with results obtained by gas chromatography-mass spectrometry and two commercial immunoassays

Background

Determination of urinary free cortisol (UFC) is an important adjunct for the assessment of adrenal function. In this study, we have analysed cortisol concentrations in urine samples by gas chromatography-mass spectrometry (GC-MS), liquid chromatography-tandem mass spectrometry (LC-MS/MS) and two immunoassays. The results were compared with GC-MS. The interference of cortisol ring-A metabolites in immunoassays was also assessed.

Methods

The GC-MS technique involved solvent extraction, LH-20 clean-up and derivatization. Only solid-phase extraction procedure was used for LC-MS/MS. The samples were analysed in positive electro-spray ionization mode, monitoring the transitions for cortisol and deuterated-cortisol at m/z 363.3 > 121.2 and m/z 365.3 > 122.2, respectively. Immunoassays were performed according to the manufacturer's instructions.

Results

When compared with GC-MS results both immunoassays (Coat-A-Count; approximately 1.9-fold, Centaur; approximately 1.6-fold) overestimated UFC concentrations. Cortisol ring-A dihydro- and tetrahydrometabolites contribute significantly to this overestimation. There was no interference by these metabolites in either GC-MS or LC-MS/MS methods. The sensitivity of the LC-MS/MS procedure was 2 nmol/L and the intra- and inter-assay variations were <5% in each quality-control sample. The comparison of the UFC results achieved by assaying the study samples with GC-MS and LC-MS/MS indicated that the agreement between the two methods was excellent (LC-MS/MS = 1.0036GC-MS – 0.0841; r 2 = 0.9937).

Conclusions

The interference of cortisol ring-A metabolites in immunoassays contribute to overestimation of UFC concentrations. The LC-MS/MS procedure had the sensitivity, specificity, linearity, precision and accuracy for the determination of UFC concentrations. The method is suitable for routine use provided that method-dependant reference values are established.

Evidence-based laboratory medicine as a tool for continuous professional improvement

BACKGROUND

Evidence-based medicine (EBM), defined as "the conscientious, explicit, and judicious use of the current best evidence in making decisions about the care of patients," seems a tool (a "new paradigm") able to meet individual clinical experience with robust observations. EBM has been driven by the need to manage information overload by cost control and by public request for the best in diagnostics and treatment.

METHODS

The application of EBM in laboratory medicine or evidence-based laboratory medicine (EBLM) is aimed to advance clinical diagnosis by researching and disseminating new knowledge, combining methods from clinical epidemiology, statistics, and social science with the traditional pathophysiological molecular approach.

RESULTS

EBLM, by evaluating the role of diagnostic investigations in the clinical decision-making process with emphasis on measurable outcome, can help both in improving the quality of new scientific findings and in translating the results of good-quality research into everyday practice.

CONCLUSIONS

Since there is a need to integrate many educational tools to focus the strategy on promoting the implementation of best practices, the STARD proposal for robust diagnostic test primary studies, the presence of systematic reviews of high quality, and the development of valid guidelines based on the best scientific evidence may be useful to promote an a evidence-based culture for appropriateness, efficiency, and effectiveness in laboratory medicine.

Evidence-based Laboratory Medicine: Supporting Decision-Making

There is an implicit acceptance that an evidence-based culture underpins the practice of laboratory medicine, in part because it is perceived as the scientific foundation of medicine. However, several reviews of specific test procedures or technologies have shown that the evidence base is limited and in many cases flawed. One of the key deficiencies in the scientific literature on diagnostic tests often is the absence of an explicit statement of the clinical need, i.e., the clinical or operational question that the use of the test is seeking to answer. Several reviews of the literature on specific procedures have also demonstrated that the experimental methodology used is flawed with, in some cases, significant bias being introduced. Despite these limitations it is recognized that a more evidence-based approach will help in the education and training of health professionals, in the creation of a research agenda, in the production of guidelines, in the support of clinical decision-making, and in resource allocation. Furthermore, as knowledge and technologies continue to be developed, an evidence-based strategy will be critical to harnessing these developments.

The combined pituitary function test in children: an evaluation of the clinical usefulness of TRH and LHRH stimulation tests through a retrospective analysis of one hundred and twenty six cases

OBJECTIVE

The combined pituitary function test is routinely used in the endocrine investigation of short children. The TRH and luteinising hormone-releasing hormone (LHRH) response tests have been shown to be of minimal value in adults. We have evaluated the clinical utility of these tests in the context of combined pituitary function testing in children.

DESIGN

A retrospective analysis of basal hormone measurements and pituitary stimulation tests in relation to clinical assessment of pituitary function.

PATIENTS

One hundred and twenty-six children, 82 boys and 44 girls, aged 2-17 years, who had undergone pituitary function testing were studied.

RESULTS

The TSH response to TRH stimulation correlated directly with basal plasma TSH but not basal plasma total T4. In patients with an impaired response to stimulation, basal TSH concentrations were <2.0 mIU/l and significantly lower than in patients with a normal response (P < 0.0001). An impaired response to TRH stimulation had a positive predictive value of 0.43 and a negative predictive value of 0.90 for the diagnosis of hypopituitarism. A basal TSH concentration of <2.0 mIU/l had a positive predictive value of 0.22 and a negative predictive value of 0.92. A low basal T4 (normal range 60-140 nmol/l) in combination with an inappropriately low or normal basal TSH was always associated with a diagnosis of hypopituitarism. The responses of plasma LH and FSH to LHRH stimulation correlated directly with basal plasma LH and FSH concentrations. Basal gonadotrophin concentrations, basal sex hormone concentrations or response to LHRH stimulation could not distinguish patients with constitutional delay of growth and puberty from those with hypopituitarism. There was no apparent relationship between either basal gonadotrophin concentrations or response to LHRH stimulation and clinical assessment of pituitary function. In patients ≥13 years with constitutional delay of growth and puberty the median and interquartile ranges of basal LH and FSH were 1.4 IU/l (0.7-3.6) and 2.6 IU/l (2.2-5.2) respectively. The three hypopituitary patients in this study with chronological age ≥13 years had undetectable concentrations of both gonadotrophins. The response of LH and FSH to LHRH stimulation was significantly lower in patients ≥13 years with clinical hypopituitarism than in those with intact pituitary function (P <0.02).

CONCLUSION

TRH and LHRH tests in children with short stature appear to have little value over and above the baseline hormone measurements. An abnormal response to hormone stimulation is not diagnostic of hypothalamic-pituitary disease. We have demonstrated that neither TRH nor LHRH stimulation tests should be routinely used in the investigation of children with short stature.

Pituitary incidentalomas

The optimal strategy for hormonal screening of a patient with any incidentally discovered pituitary mass is unknown. The authors' review of the endocrinologic literature supports the view that such patients are at slightly increased risk for morbidity and mortality. This risk implies a benefit of early diagnosis for at least for some of the disorders, suggesting the importance of case finding. Nevertheless, the data in Table 1 illustrate that clinically diagnosed hormone-secreting pituitary tumors are far less common than incidentalomas. Clinically, one cannot accurately determine the approximately 0.5% of patients with incidentaloma who are at increased risk among the vast majority who are not. Given the limitations of diagnostic tests, effective hormonal screening requires a sufficiently high pretest probability to limit the number of false-positive results. This condition is met to varying degrees in the patient with a small incidentally discovered pituitary mass but no signs or symptoms of hormone excess. Even the more common lesions, such as prolactinoma, are relatively rare. [table: see text] Subjecting patients to unnecessary testing and treatment is associated with risk. In addition to its initial cost, testing may result in further expense and harm as false-positive results are pursued, producing the "cascade effect" described by Mold and Stein as a "chain of events (which) tends to proceed with increasing momentum, so that the further it progresses the more difficult it is to stop." The extensive evaluations performed for some patients with incidentally discovered masses may reflect the unwillingness of many physicians to accept uncertainty, even in the case of an extremely unlikely diagnosis. This unwillingness may be driven, in part, by fear of potential malpractice liability, the failure to appreciate the influence of prevalence data on the interpretation of diagnostic testing, or other factors. The major justification for further evaluation of these patients is not so much to avoid morbidity and mortality for the rare patient who truly is at increased risk but to reassure patients in whom further testing is negative and the physician. Physicians must take care not to create inappropriate anxiety in patients by overemphasizing the importance of an incidental finding unless it is associated with a realistic clinical risk. The authors' recommendations are based on currently available information to minimize the untoward effects of the cascade. As evidence accumulates, these recommendations may need to be revised. The benefit of the diagnosis of an adrenal or pituitary disorder must be considered in the context of the patient's overall condition. Additional studies are needed to analyze the clinical utility of hormonal screening for these common radiologic findings. Data from these studies can be used to identify critical gaps in knowledge and to adopt the epidemiologic methods of evaluation of evidence that have been applied to preventive measures. One must be careful to recognize lead-time bias, in which survival can appear to be lengthened when screening simply advances the time of diagnosis, lengthening the period of time between diagnosis and death without any true prolongation of life; and length bias, which refers to the tendency of screening to detect a disproportionate number of cases of slowly progressive disease and to miss aggressive cases that, by virtue of rapid progression, are present in the population only briefly. Physicians must avoid the pitfalls of overestimation of disease prevalence and of the benefits of therapy resulting from advances in diagnostic imaging. Clinical judgment based on the best available evidence should be complemented and not replaced by laboratory data.

Clinical audit and the contribution of the laboratory to clinical outcome

Medical and clinical audit are tools introduced in an attempt to assess clinical performance. Clinical audit implementation in practice should follow that of the audit and the learning cycles. Ideally, audit should assess the outcome of clinical care. However, many audit projects concentrate on the process of care, which is more amenable to review. One of the cornerstones of audit is the setting up of agreed standards of care. This takes the form of clinical practice guidelines derived, preferably from the outcome of randomised double-blind controlled trials as the basis of evidence-based medicine. The assessment of the contribution of the clinical laboratory to patient outcome could be seen as a further extension of clinical audit in the practice of laboratory medicine. Areas where this contribution may be assessed include validity and usefulness of diagnostic tests, the assessment of analytical goals in relation to patient outcome, variation in inter-laboratory performance and its effect on decision limits and whether any measurement or set of measurements contribute to improved outcome. The practice of clinical audit and the application of evidence-based medicine are seen as powerful educational tools, though there is much work to be done to assess their contribution to clinical outcome. Randomised clinical trials could form the basis for the assessment of the value and contribution of the laboratory to the outcome.