Stability assessment of serum tumour markers: Calcitonin, chromogranin A, thyroglobulin and anti-thyroglobulin antibodies.

BACKGROUND: There is limited published data on the stability of calcitonin, chromogranin A, thyroglobulin and anti-thyroglobulin antibodies in serum. The aim of this study was to determine stability at three temperature conditions over 7 days, reflecting current laboratory practices. METHODS: Surplus serum was stored at room temperature, refrigerated and in the freezer; for 1, 3, 5 and 7 days. Samples were analysed in batch and analyte concentrations compared to that of a baseline sample. Measurement Uncertainty of the assay was used to determine the Maximal Permissible Difference and thus the stability of the analyte. RESULTS: Calcitonin was found to be stable for at least 7 days in the freezer but only 24 h refrigerated. Chromogranin A was stable for 3 days when refrigerated and only 24 h at room temperature. Thyroglobulin and anti-thyroglobulin antibodies were stable under all conditions for 7 days. CONCLUSION: This study has enabled the laboratory to increase the add-on time limit of Chromogranin A to 3 days, and up to 60 min for calcitonin and inform optimal storage and transportation conditions for referring specimens.

Multicenter Validation of the CamGFR Model for Estimated Glomerular Filtration Rate.

Important oncological management decisions rely on kidney function assessed by serum creatinine-based estimated glomerular filtration rate (eGFR). However, no large-scale multicenter comparisons of methods to determine eGFR in patients with cancer are available. To compare the performance of formulas for eGFR based on routine clinical parameters and serum creatinine not calibrated with isotope dilution mass spectrometry, we studied 3620 patients with cancer and 166 without cancer who had their glomerular filtration rate (GFR) measured with an exogenous nuclear tracer at one of seven clinical centers. The mean measured GFR was 86 mL/min. Accuracy of all models was center dependent, reflecting intercenter variability of isotope dilution mass spectrometry-creatinine measurements. CamGFR was the most accurate model for eGFR (root-mean-squared error 17.3 mL/min) followed by the Chronic Kidney Disease Epidemiology Collaboration model (root-mean-squared error 18.2 mL/min).

Oestradiol measurement during fulvestrant treatment for breast cancer.

Biochemical evaluation of menopausal status is used to inform treatment decisions, including clinical trial eligibility in women with oestrogen receptor positive breast cancer. However, fulvestrant may interfere with oestradiol immunoassays and confound accurate assessment in this context. We conducted a service evaluation of two immunoassays and an LC-MS/MS assay to determine the extent of the interference. Serum oestradiol levels were analysed by two immunoassays (Siemens Centaur XP and Abbott Architect) and liquid chromatography-tandem mass spectrometry (LC/MS/MS). Immunoassay gave higher serum oestradiol results than LC-MS/MS at low concentrations, with improved analytical sensitivity demonstrated by LC-MS/MS. Cross-reactivity of fulvestrant was observed for each immunoassay. We have shown that two commonly used immunoassays do not demonstrate the required sensitivity or specificity for the measurement of oestradiol in a breast cancer population. For patients receiving fulvestrant, spurious results may be generated that could impact treatment decisions. LC-MS/MS is recommended in this setting.

Practical guide for identifying unmet clinical needs for biomarkers.

The development and evaluation of novel biomarkers and testing strategies requires a close examination of existing clinical pathways, including mapping of current pathways and identifying areas of unmet need. This approach enables early recognition of analytical and clinical performance criteria to guide evaluation studies, in a cyclical and iterative manner, all the time keeping the clinical pathway and patient health outcomes as the key drivers in the process. The Test Evaluation Working Group of the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM TE-WG) https://www.eflm.eu/site/page/a/1158 has published a conceptual framework of the test evaluation cycle which is driven by the clinical pathway, inherent to which is the test purpose and role within the pathway that are defined by clinical need. To supplement this framework, the EFLM TE-WG has also published an interactive checklist for identifying unmet clinical needs for new biomarkers; a practical tool that laboratories, clinicians, researchers and industry can equally use in a consistent manner when new tests are developed and before they are released to the market. It is hoped that these practical tools will provide consistent and appropriate terminology in this diverse field and offer a platform that facilitates greater consultation and collaboration between all stakeholders. The checklist should assist the work of all colleagues involved in the discovery of novel biomarkers and implementation of new medical tests. The tool is aligned with the IOM recommendations and the FDA and CE regulating body's requirements.

Biomarker development targeting unmet clinical needs.

BACKGROUND: The introduction of new biomarkers can lead to inappropriate utilization of tests if they do not fill in existing gaps in clinical care. We aimed to define a strategy and checklist for identifying unmet needs for biomarkers. METHODS: A multidisciplinary working group used a 4-step process: 1/ scoping literature review; 2/ face-to-face meetings to discuss scope, strategy and checklist items; 3/ iterative process of feedback and consensus to develop the checklist; 4/ testing and refinement of checklist items using case scenarios. RESULTS: We used clinical pathway mapping to identify clinical management decisions linking biomarker testing to health outcomes and developed a 14-item checklist organized into 4 domains: 1/ identifying and 2/ verifying the unmet need; 3/ validating the intended use; and 4/ assessing the feasibility of the new biomarker to influence clinical practice and health outcome. We present an outcome-focused approach that can be used by multiple stakeholders for any medical test, irrespective of the purpose and role of testing. CONCLUSIONS: The checklist intends to achieve more efficient biomarker development and translation into practice. We propose the checklist is field tested by stakeholders, and advocate the role of the clinical laboratory professional to foster trans-sector collaboration in this regard.

Serum Cortisol: An Up-To-Date Assessment of Routine Assay Performance.

BACKGROUND: Accurate serum cortisol quantification is required for the correct diagnosis and management of adrenal pathologies. Presently, most laboratories use immunoassay to measure serum cortisol with proficiency schemes demonstrating a wide dispersion of results. Here, we investigate the effects of sex, matrix, and antibody specificity on serum cortisol quantification in 6 routine assays. METHODS: Surplus serum was obtained before disposal and the following cohorts were created: males, nonpregnant females, pregnant patients, and patients prescribed either metyrapone or prednisolone. Samples were anonymized and distributed to collaborating laboratories for cortisol analysis by 6 routine assays. Cortisol was also measured in all samples using an LC-MS/MS candidate reference measurement procedure (cRMP); cortisol-binding globulin (CBG) was measured in the nonpregnant and pregnant female cohorts. RESULTS: Considerable inter- and intraassay variation was observed across the male and nonpregnant female cohorts relative to the cRMP. Four immunoassays underrecovered cortisol in the pregnancy cohort, and CBG was found to be significantly higher in this cohort than in the nonpregnant females. In the metyrapone and prednisolone cohorts, all immunoassays overestimated cortisol. The first generation Roche E170 and Siemens Centaur XP were particularly prone to overestimation. In all cohorts the routine LC-MS/MS assay aligned extremely well with the cRMP. CONCLUSIONS: Despite the clinical importance of serum cortisol, the performance of routine immunoassays remains highly variable. Accurate quantification is compromised by both matrix effects and antibody specificity. Underpinning this study with a cRMP has highlighted the deficiencies in standardization across routine cortisol immunoassays.

Serum and plasma 5-hydroxyindoleacetic acid as an alternative to 24-h urine 5-hydroxyindoleacetic acid measurement.

BACKGROUND: Neuroendocrine tumours are slow growing tumours known to secrete a variety of vasoactive peptides which give rise to symptoms of the carcinoid syndrome. The diagnosis and monitoring of patients with neuroendocrine tumours is undertaken in many centres using 24 h urinary measurement of 5-hydroxyindoleacetic acid. However, 5-hydroxyindoleacetic acid can also be quantified in plasma and serum. METHODS: We measured 5-hydroxyindoleacetic acid concentration in 134 paired EDTA plasma and urine samples from 108 patients with known neuroendocrine tumours and 26 healthy volunteers. We also compared 5-hydroxyindoleacetic acid concentrations in paired serum and plasma samples (n = 63), then analysed paired urine and serum samples (n = 97). Furthermore, we examined the impact of renal impairment on serum 5-hydroxyindoleacetic acid by analysing 5-hydroxyindoleacetic acid in patients without neuroendocrine tumours in different stages of chronic kidney disease, as indicated by the estimated glomerular filtration rate. RESULTS: Plasma and urine 5-hydroxyindoleacetic acid had very similar diagnostic sensitivities and specificities, with areas under the curve on ROC analysis of 0.917 and 0.920, respectively. Serum and plasma 5-hydroxyindoleacetic acid values showed good correlation but serum results demonstrated a positive bias, indicating the necessity for different serum and plasma reference intervals. There was an inverse correlation between estimated glomerular filtration rate and serum 5-hydroxyindoleacetic acid concentration, with 5-hydroxyindoleacetic acid increasing once the estimated glomerular filtration rate falls below 60 mL/min/1.73 m(2). CONCLUSION: The measurement of both serum and plasma 5-hydroxyindoleacetic acid can be used for the diagnosis and monitoring of patients with neuroendocrine tumours. Provided renal function is taken into consideration, either of these tests should be incorporated into standard practice as an alternative assay to urinary 5-hydroxyindoleacetic acid.

Setting analytical performance specifications based on outcome studies - is it possible?

The 1st Strategic Conference of the European Federation of Clinical Chemistry and Laboratory Medicine proposed a simplified hierarchy for setting analytical performance specifications (APS). The top two levels of the 1999 Stockholm hierarchy, i.e., evaluation of the effect of analytical performance on clinical outcomes and clinical decisions have been proposed to be replaced by one outcome-based model. This model can be supported by: (1a) direct outcome studies; and (1b) indirect outcome studies investigating the impact of analytical performance of the test on clinical classifications or decisions and thereby on the probability of patient relevant clinical outcomes. This paper reviews the need for outcome-based specifications, the most relevant types of outcomes to be considered, and the challenges and limitations faced when setting outcome-based APS. The methods of Model 1a and b are discussed and examples are provided for how outcome data can be translated to APS using the linked evidence and simulation or decision analytic techniques. Outcome-based APS should primarily reflect the clinical needs of patients; should be tailored to the purpose, role and significance of the test in a well defined clinical pathway; and should be defined at a level that achieves net health benefit for patients at reasonable costs. Whilst it is acknowledged that direct evaluations are difficult and may not be possible for all measurands, all other forms of setting APS should be weighed against that standard, and regarded as approximations. Better definition of the relationship between the analytical performance of tests and health outcomes can be used to set analytical performance criteria that aim to improve the clinical and cost-effectiveness of laboratory tests.

From biomarkers to medical tests: the changing landscape of test evaluation.

Regulators and healthcare payers are increasingly demanding evidence that biomarkers deliver patient benefits to justify their use in clinical practice. Laboratory professionals need to be familiar with these evidence requirements to better engage in biomarker research and decisions about their appropriate use. This paper by a multidisciplinary group of the European Federation of Clinical Chemistry and Laboratory Medicine describes the pathway of a laboratory assay measuring a biomarker to becoming a medically useful test. We define the key terms, principles and components of the test evaluation process. Unlike previously described linearly staged models, we illustrate how the essential components of analytical and clinical performances, clinical and cost-effectiveness and the broader impact of testing assemble in a dynamic cycle. We highlight the importance of defining clinical goals and how the intended application of the biomarker in the clinical pathway should drive each component of test evaluation. This approach emphasizes the interaction of the different components, and that clinical effectiveness data should be fed back to refine analytical and clinical performances to achieve improved outcomes. The framework aims to support the understanding of key stakeholders. The laboratory profession needs to strengthen collaboration with industry and experts in evidence-based medicine, regulatory bodies and policy makers for better decisions about the use of new and existing medical tests.

Rome III functional constipation and irritable bowel syndrome with constipation are similar disorders within a spectrum of sensitization, regulated by serotonin.

BACKGROUND & AIMS: Patients with irritable bowel syndrome with constipation (IBS-C) and patients with functional constipation (FC) have similar symptoms, and these disorders overlap in their diagnostic features. Little is known about their overlap in physiology or the involvement of serotonin signaling. We investigated relationships between platelet-depleted plasma concentrations of serotonin, gastrointestinal symptoms, and motor-sensory function in patients with FC or IBS-C compared with healthy volunteers (controls). METHODS: We measured platelet-depleted plasma concentrations of serotonin in fasting and fed individuals with IBS-C (n = 23; 19-50 years old), FC (n = 11; 25-46 years old), and controls (n = 23; 20-49 years old) recruited in Manchester, UK. We also quantified abdominal and bowel-related symptoms, rectal sensitivity, oro-cecal transit, and colonic (whole intestine) transit. RESULTS: Patients with IBS-C or FC had similar baseline symptoms, bowel habits, oro-cecal and colonic transit, and fasting concentrations of serotonin and response to meal ingestion. Only patients with IBS-C had increased symptoms after ingestion of a meal (P < .001)-these patients tended to have lower sensory thresholds than patients with FC. Defecation frequency in the combined group of patients with IBS-C or FC correlated inversely with serotonin concentration (r = -0.4; P = .03). Serotonin concentration also correlated with pain threshold (r = 0.4; P = .02) and stool threshold (r = 0.5; P = .06), which correlated inversely with defecation frequency (r = -0.3; P = .10). CONCLUSIONS: FC and IBS-C, based on Rome III criteria, are not distinct disorders, symptomatically or physiologically. Instead, they appear to lie in a spectrum of visceral sensitivity modulated by serotonin signaling. Symptom response to meal ingestion should be considered in patient classification.

The use of mass spectrometry to improve the diagnosis and the management of the HPA axis.

Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) is becoming a standard analytical tool in the clinical laboratory for the measurement of small molecules, including steroid hormones. Endocrinologists are coming to acknowledge the superior quality of measurement that is achievable by LC-MS/MS through the enhanced analytical specificity and high sensitivity that this technique offers over conventional immunoassay (IA) methodologies. Additionally, LC-MS/MS overcomes many of the problems encountered in immunoassays, such as anti-reagent antibody interferences and cross-reactivity with structurally related compounds. The potential benefits of applying LC-MS/MS for the assessment of the hypothalamic-pituitary-adrenal (HPA) axis are beginning to be realised. This review critically evaluates recent developments in the application of LC-MS/MS for measurement of glucocorticoids and mineralocorticoids towards the diagnosis and management of HPA axis disorders and aims to address the current unmet need in this expanding field of endocrinology for which future studies into the potential applications of LC-MS/MS should be directed.