Rapid determination of serum testosterone by liquid chromatography-isotope dilution tandem mass spectrometry and a split sample comparison with three automated immunoassays

The experience in the development and validation of method for testosterone measurement in blood serum of premenopausal women using HPLC-MS/MS

Testosterone assessment is essential for detecting biochemical hyperandrogenism, one of the important diagnostic criteria of polycystic ovary syndrome (PCOS) both in clinical practice and in epidemiological studies. Currently, tandem liquid chromatography-mass spectrometry (LC-MS/MS) is the most preferred technique to measure testosterone level in women. Its validation is important to reproducibility of androgen tests results for clinical practice and for epidemiological studies of the prevalence PCOS.The aim of the study. To develop and validate a method for determining total testosterone in blood serum using highly efficient LC-MS/MS to assess androgenemia in the epidemiological study of the prevalence of PCOS and its phenotypes in Eastern Siberia (ESPEP STUDY).Materials and methods. We determined a total testosterone level in serum blood using triple quadrupole mass spectrometer LCMS-8060 (Shimadzu, Japan). The protocol of technique was developed using self-prepared purified human testosteronefree serum with a known concentration of analyzed compound. We used the serum samples of women of reproductive age to test the developed method.Results. Optimum chromatographic conditions were obtained with a Kromasil 100-2.5-C18 column (2.1 mm × 100 mm; AkzoNobel, Netherlands), and an isocratic elution mode using a mobile phase consisting of acetonitrile and 0.1 % aqueous solution of formic acid. The total flow rate was 0.35 ml/min. The lower limit of quantification was 5 ng/dl with an average accuracy of 100.2 %. During the approbation of the method in a test population sample of 1138 premenopausal women (mean age – 34.3 ± 6.3 years), the median testosterone concentration was 26.9 ng/dl.Conclusion. It was found that the proposed method for determining testosterone in blood serum has acceptable linearity and reproducibility and meets the requirements for bioanalytical methods under the regulatory documentation. This method can be used for clinical practice and epidemiological study of the prevalence of PCOS.

Tb3+-atorvastatin doped in poly(ethylene glycol) optical biosensor for selective determination of progesterone and testosterone in serum samples

An innovative, simple and cost effective Tb3+-atorvastatin photo probe was designed and used as a core for a spectrofluorometric approach to sensitively determine two vital biological compounds in serum samples. Tb3+-atorvastatin complex displays a characteristic electrical band with λ em at 545 nm with significant luminescence intensity, which is quenched in the presence of progesterone and testosterone at two variant sets of pH; 6.2 and 7.5, respectively. The conditions were optimized and the best solvent for operation was found to be acetonitrile with λ ex at 320 nm. Progesterone and testosterone were assessed in serum samples using the same optimal conditions within concentration ranges of 2 × 10-9 to 2.9 × 10-6 and 3.1 × 10-9 to 4.8 × 10-6 mol L-1, respectively. The proposed luminescence method was validated in accordance to ICH guidelines and found to be accurate, precise and specific and free from any interference. The cost effectiveness and applicability of the method make it a good choice for routine analysis of the two compounds and early diagnosis of chronic diseases associated with abnormalities in their physiological levels.

New Tb3+–simvastatin optical biosensor for sensitive determination of folic acid, progesterone, testosterone and vitamin D3 in biological fluids

An innovative, simple and cost effective Tb3+–simvastatin photo probe was designed and used as a core for a spectrofluorometric approach to sensitively determine four vital biological compounds in different matrices.

Liquid chromatography-mass spectrometry applications for quantification of endogenous sex hormones

Liquid chromatography, coupled with tandem mass spectrometry, presents a powerful tool for the quantification of the sex steroid hormones 17-β estradiol, progesterone and testosterone from biological matrices. The importance of accurate quantification with these hormones, even at endogenous levels, has evolved with our understanding of the role these regulators play in human development, fertility and disease risk and manifestation. Routine monitoring of these analytes can be accomplished by immunoassay techniques, which face limitations on specificity and sensitivity, or using gas chromatography-mass spectrometry. LC-MS/MS is growing in capability and acceptance for clinically relevant quantification of sex steroid hormones in biological matrices and is able to overcome many of the limitations of immunoassays. Analyte specificity has improved through the use of novel derivatizing agents, and sensitivity has been refined through the use of high-resolution chromatography and mass spectrometric technology. This review highlights these innovations, among others, in LC-MS/MS steroid hormone analysis captured in the literature over the last decade.

Analytical bias of automated immunoassays for six serum steroid hormones assessed by LC-MS/MS

Introduction

There is a growing amount of evidence showing the significant analytical bias of steroid hormone immunoassays, but large number of available immunoassays makes conduction of a single comprehensive study of this issue hardly feasible. Aim of this study was to assess the analytical bias of six heterogeneous immunoassays for serum aldosterone, cortisol, dehydroepiandrosterone sulphate (DHEAS), testosterone, 17-hydroxyprogesterone (OHP) and progesterone using the liquid chromatography coupled to the tandem mass spectrometry (LC-MS/MS).

Materials and methods

This method comparison study included 49 serum samples. Testosterone, DHEAS, progesterone and cortisol immunoassays were performed on the Abbott Architect i2000SR or Alinity i analysers (Abbott Diagnostics, Chicago, USA). DiaSorin’s Liaison (DiaSorin, Saluggia, Italy) and DIAsource’s ETI-Max 3000 analysers (DIAsource ImmunoAssays, Louvain-La-Neuve, Belgium) were chosen for aldosterone and OHP immunoassay testing, respectively. All immunoassays were evaluated against the LC-MS/MS assay relying on the commercial kit (Chromsystems, Gräfelfing, Germany) and LCMS-8050 analyser (Shimadzu, Kyoto, Japan). Analytical biases were calculated and method comparison was conducted using weighted Deming regression analysis.

Results

Depending on the analyte and specific immunoassay, mean relative biases ranged from -31 to + 137%. Except for the cortisol, immunoassays were positively biased. For none of the selected steroids slope and intercept 95% confidence intervals simultaneously contained 0 and 1, respectively.

Conclusions

Evaluated immunoassays failed to satisfy requirements for methods’ comparability and produced significant analytical biases in respect to the LC-MS/MS assay, especially at low concentrations.

Discordance between testosterone measurement methods in castrated prostate cancer patients

Failure to suppress testosterone below 0.7 nM in castrated prostate cancer patients is associated with poor clinical outcomes. Testosterone levels in castrated patients are therefore routinely measured. Although mass spectrometry is the gold standard used to measure testosterone, most hospitals use an immunoassay method. In this study, we sought to evaluate the accuracy of an immunoassay method to measure castrate testosterone levels, with mass spectrometry as the reference standard. We retrospectively evaluated a cohort of 435 serum samples retrieved from castrated prostate cancer patients from April to September 2017. No follow-up of clinical outcomes was performed. Serum testosterone levels were measured in the same sample using liquid chromatography coupled with tandem mass spectrometry and electrochemiluminescent immunoassay methods. The mean testosterone levels were significantly higher with immunoassay than with mass spectrometry (0.672 ± 0.359 vs 0.461 ± 0.541 nM; P < 0.0001). Half of the samples with testosterone ≥0.7 nM assessed by immunoassay were measured <0.7 nM using mass spectrometry. However, we observed that only 2.95% of the samples with testosterone <0.7 nM measured by immunoassay were quantified ≥0.7 nM using mass spectrometry. The percentage of serum samples experiencing testosterone breakthrough at >0.7 nM was significantly higher with immunoassay (22.1%) than with mass spectrometry (13.1%; P < 0.0001). Quantitative measurement of serum testosterone levels >0.7 nM by immunoassay can result in an inaccurately identified castration status. Suboptimal testosterone levels in castrated patients should be confirmed by either mass spectrometry or an immunoassay method validated at low testosterone levels and interpreted with caution before any changes are made to treatment management.

Comparison of four clinically validated testosterone LC-MS/MS assays: Harmonization is an attainable goal

Introduction

Immunoassays and liquid chromatography-tandem mass spectrometry assays are commonly employed in clinical laboratories for measurement of total testosterone in serum. Results obtained from either of these methodologies compare poorly due to differences in calibration and/or inadvertent detection of interfering substances by the immunoassays. Standardization efforts are underway, but recent studies indicate that accuracy remains an issue.

Methods

This study compares the results from four independently developed and validated LC-MS/MS assays for total testosterone. The calibration for each assay was verified using National Institute of Standards and Technology Standard Reference Material 971.

Results

Initially, one of the four assays had a mean percent difference of +11.44%, compared to the All Method Mean, but following re-verification of all five non-zero calibrator concentrations with the NIST SRM 971, the mean percent difference decreased to -4.88%. Subsequently, the agreement between all four assays showed a mean bias of <5% across the range of all testosterone concentrations (0.13-38.10 nmol/L; 3.7-1098 ng/dL), including at low concentrations of <1 nmol/L (<29 ng/dL).

Conclusions

Excellent agreement between four independently developed LC-MS/MS assays demonstrates that harmonization using standard reference material is attainable. However, as we found in this study, to ensure accurate calibration it is critical to validate the concentrations of new lots of calibrators.

Photonic Molecularly Imprinted Polymer Film for the Detection of Testosterone in Aqueous Samples

The detection of testosterone in aqueous solutions is a difficult task due to the low concentration levels that are relevant in environmental and physiological samples. Current analytical methods are expensive and/or complex. To address this issue, we fabricated a molecularly imprinted polymer (MIP) photonic film for the detection of testosterone in water. The films were obtained using colloidal crystals as templates for the pore morphology. Monodispersed silica particles with an average diameter 330 nm were used to obtain the colloidal crystal by vertical deposition. A solution of acrylic acid with testosterone as the imprinted template was infiltrated in the colloidal crystal and polymerized via bulk polymerization; the particles were then removed by acid etching and the testosterone eluted by a suitable solvent. The material was characterized by FTIR, swelling experiments and microscopy; MIPs were investigated by equilibrium rebinding, kinetics and reuse experiments. The results showed that the MIPs exhibited selectivity to the template, a 30-min equilibration time and stability after at least six cycles of use and regeneration. After incubation, the reflectance spectra of the films showed a shift of the Bragg diffraction peak that correlated with testosterone concentration in the 5–100 ppb range.

The Simultaneous measurement of serum testosterone and 5α-dihydrotestosterone by gas chromatography-mass spectrometry (GC-MS)

BACKGROUND

Simultaneous measurement of testosterone (T) and 5α-dihydrotestosterone (DHT) is important for diagnosing androgen deficiency states and hyperandrogenism in males and females, respectively. However, immunoassays used for T and DHT determination suffer from inadequate specificity and sensitivity, while tandem mass spectrometry is expensive and demanding in use.

METHODS AND RESULTS

We developed a selective gas chromatography-mass spectrometry (GC-MS) method for parallel T and DHT measurement. The assay showed a linear response up to 46.5nmol/L, intra- and interassay imprecision and inaccuracy <15% and recoveries in spiked samples >90% for both analytes. The limit of quantitation was 0.117nmol/L for T and 0.168nmol/L for DHT. Comparison with immunoassays revealed good agreement for T in males, but a bias in favour of immunoassays at low concentrations for T in females and DHT in both sexes. We established reference ranges for T and DHT and suggest interval partitioning for T according to age in men and menstrual cycle in women. Assay validation in a clinical setting suggests that measuring DHT or T/DHT ratio may help identify patients with polycystic ovary syndrome.

CONCLUSION

We developed a selective, simple and inexpensive GC-MS method for parallel measurement of T and DHT with potential use in the clinical laboratory.

Evaluation of new Beckman Coulter 25(OH) Vitamin D assay and potential improvement of clinical interpretation

INTRODUCTION

The aim of this study was to assess the analytical performances of the newly developed Access2 25-hydroxyvitamin D (25(OH)D) total immunoassay on two analysers, DxI800 and Access2 (Beckman Coulter, Brea, CA, USA), and compare these two and a recalibrated Modular E 170 25(OH)D assay (Roche Diagnostics, Penzberg, Germany) with reference liquid chromatography tandem-mass spectrometry (LC-MS/MS) with special emphasis on clinical diagnosis.

MATERIALS AND METHODS

Beckman immunoassays were assessed for imprecision, accuracy, limit of blank (LoB), limit of detection (LoD), limit of quantitation (LoQ), linearity, interference, and carryover. One hundred and nineteen samples were run on DxI 800, Access2, and E 170, and agreement with the LC-MS/MS method was evaluated.

RESULTS

DxI 800 and Access2 assays showed good performances in terms of LoB, LoD, LoQ, linearity, and interference. All immunoassays showed negative biases ranging from - 8.6% (DxI 800) to - 19.2% (Access2). DxI 800 and Access2 systems had proportional biases, and the E170 system had a constant bias with the largest random error. Concordance correlation coefficient values ranged from 0.941 (CI: 0.917-0.958) for DxI800 to 0.854 (CI: 0.811-0.889) for Access2. Kappa (κ) coefficients were found moderate for Dxl (0.709; CI: 0.581-0.837) and E170 (0.771; CI: 0.587-0.844) and fair for Access2 (0.572; CI: 0.428-0.716).

CONCLUSIONS

All immunoassays can be used in routine 25(OH)D measurements, still fairly diagnosing patients' status. Recent standardization attempts seem not to contribute too much to clinical diagnosis. A clinical laboratory must at least be aware of its method to avoid misinterpretation of results.

Levels of the natural hormones 17β-oestradiol and testosterone in serum of cattle: results from population studies in Poland

Introduction: The present study is a comprehensive overview of the natural occurrence of 17β-oestradiol and testosterone in serum of cattle in Poland. Material and Methods: The serum samples (n = 826) were collected from cattle within five years. The samples were examined for the presence of oestradiol and testosterone using ELISA or gas chromatography with mass spectrometry. Results: In 98 samples (24%) 17β-oestradiol was detected above decision limits of applied methods, including five samples over the recommended concentration of 0.1 μg L-1. Of the serum samples taken from cows (≤18 months of age), 95 and 99 percentiles of the animals had 17β-oestradiol concentration below 0.027 and 0.086 μg L-1 and of samples from cows over 18 months of age - below 0.059 and 0.125 μg L-1 respectively. Calculated values for bulls (≤18 months of age) were 0.025 and 0.034 μg L-1 and for the animals older than 18 months of age - 0.035 and 0.041 μg L-1. The natural presence of testosterone was detected in 201 serum samples (48.7%). According to the obtained data, 95% and 99% of cows (≤18 months of age) serum samples had testosterone concentration below 0.05 and 0.23 μg L-1 and the animals over 18 months of age - 0.30 and 0.49 μg L-1, respectively. For bulls these values did not depend on the age of the animals and were in the ranges of 5 - 6.3 μg L-1 (95%) and 11.4 - 12.1 μg L-1 (99%). Conclusion: Our study showed that the threshold values for these hormones in plasma of cattle designated years ago are correct, but they need to be supplemented for animals older than 18 months.

Chemical derivatization for enhancing sensitivity during LC/ESI-MS/MS quantification of steroids in biological samples: a review

Sensitive and specific methods for the detection, characterization and quantification of endogenous steroids in body fluids or tissues are necessary for the diagnosis, pathological analysis and treatment of many diseases. Recently, liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) has been widely used for these purposes due to its specificity and versatility. However, the ESI efficiency and fragmentation behavior of some steroids are poor, which lead to a low sensitivity. Chemical derivatization is one of the most effective methods to improve the detection characteristics of steroids in ESI-MS/MS. Based on this background, this article reviews the recent advances in chemical derivatization for the trace quantification of steroids in biological samples by LC/ESI-MS/MS. The derivatization in ESI-MS/MS is based on tagging a proton-affinitive or permanently charged moiety on the target steroid. Introduction/formation of a fragmentable moiety suitable for the selected reaction monitoring by the derivatization also enhances the sensitivity. The stable isotope-coded derivatization procedures for the steroid analysis are also described.

Behavior of total and free serum testosterone as a predictor for the risk of prostate cancer and its aggressiveness

CONTEXT

Serum testosterone is mostly bound to the sex hormone-binding globulin and albumin. A small metabolically active part is present in the form of free testosterone (FT). The relationship between serum total testosterone (TT) levels and prostate carcinogenesis is debated. Our hypothesis is that the serum FT concentration is more closely associated with the risk of prostate cancer (PC) and its aggressiveness than TT.

OBJECTIVE

To analyze the scientific evidence that relates serum TT and/or FT levels with the diagnosis of PC and its aggressiveness.

ACQUISITION OF EVIDENCE

A systematic review was conducted in PubMed up to January 2015 using the following mesh terms: prostate cancer, sex hormone, androgen, testosterone and free testosterone.

SYNTHESIS OF THE EVIDENCE

We found 460 publications, 124 of which were reviewed to analyze the evidence. The relationship between serum TT levels and the diagnosis of PC and its aggressiveness is highly heterogeneous. The variability in the design of the studies, the quantification methods and other variables could explain this heterogeneity. In a number of studies that evaluated the estimated or measured FT, the evidence remains equally conflicting.

CONCLUSIONS

Based on the current evidence, we cannot recommend the measurement of serum TT and/or TL levels for the diagnosis of PC or for assessing its aggressiveness.

Accuracy of testosterone concentrations in compounded testosterone products

OBJECTIVE

This study aims to evaluate the accuracy of the testosterone concentrations within testosterone gels and creams manufactured by compounding pharmacies.

METHODS

Ten compounding pharmacies within Toronto area were included. Pharmacies were blinded as to the nature of the study. A standardized prescription for 50 mg of compounded testosterone gel/cream applied once daily was presented to each pharmacy. Two independently compounded batches were analyzed from each pharmacy 1 month apart. Testosterone concentrations in a 5-g sachet of Androgel® 1% (Abbott) and 5-g tube of Testim®1% (Auxilium) were evaluated as controls. Samples were analyzed independently and in a blinded fashion by the Laboratory Medicine Program at the University Health Network. Measurement of testosterone concentration was performed using a modified liquid chromatography tandem mass spectrometry validated for serum testosterone.

RESULTS

Compounded formulations included seven gels and three creams with a volume/daily dose ranging from 0.2 mL to 1.25 mL. Product cost ranged from $57.32 to $160.71 for a 30-day supply. There was significant variability both within and between pharmacies with respect to the measured concentration of testosterone in the compounded products. In contrast, the concentration of testosterone within Androgel and Testim was consistent and accurate. Collectively, only 50% (batch 1) and 30% (batch 2) of the compounding pharmacies provided a product with a testosterone concentration within ± 20% of the prescribed dose. Two pharmacies compounded products with >20% of the prescribed dose. One pharmacy compounded a product with essentially no testosterone.

CONCLUSIONS

Testosterone concentrations in compounded testosterone products can be variable and potentially compromise the efficacy and safety of treatment.

Free testosterone: clinical utility and important analytical aspects of measurement

Testosterone, the most abundant androgen in men, is a steroid hormone that is synthesized predominantly by the testes. In women, minor amounts are synthesized in the ovaries. Androgen precursors are also produced and secreted from the adrenal glands in both sexes, where they undergo peripheral conversion to testosterone. Circulating concentrations are approximately 15-25 times higher in adult men compared to women. Maintenance of these levels is necessary for development and maintenance of secondary sexual characteristics, libido, growth, prevention of osteoporosis, and most importantly in men, spermatogenesis. Most testosterone circulates tightly bound to sex hormone-binding globulin (SHBG) or weakly bound to albumin. A minor amount circulates as free testosterone, and it is believed that this is the metabolically active fraction. Measurement of free testosterone is important in the diagnosis of many diseases, most importantly disorders of androgen deficiency in men (i.e., hypogonadism) and androgen excess in women (i.e., polycystic ovary syndrome and hirsutism). Many methodologies are available for free testosterone measurement including the reference methods (equilibrium dialysis and ultrafiltration), analog immunoassay, and calculated free testosterone based on measurement of total testosterone, SHBG, and albumin. Moreover, measurement of bioavailable testosterone, a combination of albumin-bound and free testosterone, also has clinical utility and can be measured by selective protein precipitation or calculation. In this review, the advantages and limitations of each of these methods will be discussed in the context of clinical utility and implementation into a routine hospital laboratory. Furthermore, up and coming methodologies for free testosterone measurement, including liquid chromatography-tandem mass spectrometry, will also be discussed.

A multicenter evaluation of immunoassays for follicle-stimulating hormone, luteinizing hormone and testosterone: concordance, imprecision and reference values

BACKGROUND

Numerous laboratories in Italy use radioimmunoassay to determine concentrations of sex hormones (FSH, LH, testosterone). A comparison of assay methods is thus an important starting point for the achievement of universally accepted reference values.

AIM

To carry out an external quality assessment for FSH, LH, and testosterone.

MATERIALS AND METHODS

Fifteen aliquots from 5 serum pools were assayed in multiple replicates by 16 Italian laboratories with 5 automated immunoassays (Abbott Architect, DiaSorin Liaison, Perkin-Elmer AutoDelfia, Roche Elecsys, Siemens Immulite 2000), and 1 radioimmunoassay (Adaltis).

RESULTS

The variance was below 12% for FSH, between 11.61% and 14.76% for LH, and between 9.57% and 12.48% for testosterone. Assay precision was good, except for Elecsys at low concentrations of FSH and for Immulite at low concentrations of LH and testosterone. ARCHITECT showed a negative bias for FSH and LH and a positive bias for testosterone; Liaison a positive bias for LH; Elecsys a positive bias for FSH and a negative bias for testosterone; Immulite a positive bias for FSH; AutoDelfia a negative bias for FSH and a positive bias for testosterone. Reference ranges at the low end varied widely, even among laboratories using the same assay.

CONCLUSIONS

The analytical performances of widely used immunoassays for FSH, LH, and testosterone show a fair to strong degree of consistency. A careful evaluation of reference ranges by clinical and laboratory experts needs to be carried out, in order to reach a consensus.

Revisiting hyper- and hypo-androgenism by tandem mass spectrometry

Modern endocrinology is living a critical age of transition as far as laboratory testing and biochemical diagnosis are concerned. Novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays for steroid measurement in biological fluids have abundantly demonstrated their analytical superiority over immunometric platforms that until now have dominated the world of steroid hormones determination in clinical laboratories. One of the most useful applications of LC-MS/MS is in the hypogonadism and hyperandrogenism field: LC-MS/MS has proved particularly suitable for the detection of low levels of testosterone typical of women and children, and in general more reliable in accurately determining hypogonadal male levels. This technique also offers increased informative power by allowing multi-analytical profiles that give a more comprehensive picture of the overall hormonal asset. Several LC-MS/MS methods for testosterone have been published in the last decade, some of them included other androgen or more comprehensive steroid profiles. LC-MS/MS offers the concrete possibility of achieving a definitive standardization of testosterone measurements and the generation of widely accepted reference intervals, that will set the basis for a consensus on the diagnostic value of biochemical testing. The present review is aimed at summarizing technological advancements in androgen measurements in serum and saliva. We also provide a picture of the state of advancement of standardization of testosterone assays, of the redefinition of androgen reference intervals by novel assays and of studies using LC-MS/MS for the characterization and diagnosis of female hyperandrogenism and male hypogonadism.

Tandem mass spectrometry in hormone measurement

Mass spectrometry methods have the potential to measure different hormones during the same analysis and have improved specificity and a wide analytical range compared with many immunoassay methods. Increasingly in clinical laboratories liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays are replacing immunoassays for the routine measurement of testosterone, 17-hydroxyprogesterone, and other steroid hormones. Reference LC-MS/MS methods for steroid, thyroid, and peptide hormones are being used for assessment of the performance and calibration of commercial immunoassays. In this chapter, the general principles of tandem mass spectrometry and examples of hormone assays are described.

Performance evaluation of Siemens ADVIA Centaur and Roche MODULAR Analytics E170 Total 25-OH Vitamin D assays

OBJECTIVES

To evaluate the newly developed Roche MODULAR Analytics E170 Total Vitamin D and the Siemens ADVIA Centaur Vitamin D Total assays.

MATERIALS AND METHODS

Assays were evaluated using the Clinical and Laboratory Standards Institute protocols. Split patient samples were compared with LC-MS/MS and DiaSorin LIAISON assays (n=79 including 15 specimens with detectable endogenous 25-OH vitamin D(2)). Assay accuracy was also evaluated using the Vitamin D External Quality Assessment Scheme (DEQAS) samples.

RESULTS

The ADVIA Centaur and E170 assays demonstrated maximum total CVs of 14.1% and 5.9%, respectively. Both showed excellent linearity (R(2)>0.99). The ADVIA Centaur assay demonstrated interference with bilirubin at 800 μmol/L, hemolysis at 1.25 g/L, and triglycerides at 2.8 mmol/L. Compared to LC-MS/MS, the ADVIA Centaur assay demonstrated a R(2) value of 0.893, average bias of -8.8%; the E170 assay an R(2) value of 0.872, average bias of 14.3% with underestimation of 25-OH vitamin D(2). Compared to the LIAISON assay, the ADVIA Centaur assay demonstrated an R(2) value of 0.781, average bias of -17.3%; the E170 assay an R(2) value of 0.823, average bias of 11.4%. The ADVIA Centaur and E170 assays demonstrated a biases of <20% in 10/10 and 8/10 DEQAS samples, respectively.

CONCLUSIONS

The ADVIA Centaur and E170 vitamin D assays demonstrated acceptable linearity, imprecision, and accuracy. The E170 assay demonstrated consistent underestimation of 25-OH vitamin D(2) levels. Compared with LC-MS/MS, the ADVIA Centaur assay demonstrated a higher R(2) value and a smaller average bias than the E170 assay.

Performance evaluation of Siemens ADVIA Centaur enhanced estradiol assay and a split sample comparison with liquid chromatography-tandem mass spectrometry

OBJECTIVES

The objective of this study was to evaluate the newly developed Siemens ADVIA Centaur enhanced Estradiol (eE2) assay and compare it with a well-established estradiol liquid chromatography-tandem mass spectrometry (LC-MS/MS) method.

DESIGN AND METHODS

The Siemens eE2 assay was evaluated using the Clinical and Laboratory Standards Institute evaluation protocols. Split patient samples were compared with the eE2 assay, the current ADVIA Centaur E2-6 Ill assay; and LC-MS/MS method by API5000 mass spectrometer.

RESULTS

Within-run and total imprecision of the eE2 assay demonstrated coefficient of variations of 5.7%, 3.2%, 1.5%, and 10.4%, 7.3%, and 6.8%, at levels of 380, 752, and 2051 pmol/L, respectively. The method comparisons showed: eE2=0.903(E2-6 III) -16.2, R(2)=0.938, average bias=-12.3%; and eE2=0.946(LC-MS/MS)+19.5, R(2)=0.925, average bias: 0%.

CONCLUSION

The Siemens eE2 assay correlates well with LC-MS/MS. This method is reliable, and appropriate for routine clinical laboratory use.

Challenges and benefits of endogenous steroid analysis by LC–MS/MS

Quantification of endogenous hormonal steroids and their precursors is essential for diagnosing a wide range of endocrine disorders. Historically, these analyses have been carried out using immunoassay, but such methods are problematic, especially for low-concentration analytes, due to assay interference by other endogenous steroids. MS offers improved specificity over immunoassay and can be highly sensitive. GC–MS, with use of stable isotopically labeled internal standards, is considered the ‘gold standard’ method for serum steroid analysis. GC–MS is the method of choice for profiling steroid metabolites in urine, but these techniques are not appropriate for routine use in clinical laboratories owing to a need for extensive sample preparation, as well as analytical expertise. LC–MS/MS compares well to GC–MS in terms of accuracy, precision and sensitivity, but allows simplified sample preparation. While most publications have featured only one or a limited number of steroids, we consider that steroid paneling (which we propose as the preferred term for multitargeted steroid analysis) has great potential to enable clinicians to make a definitive diagnosis. It is adaptable for use in a number of matrices, including serum, saliva and dried blood spots. However, LC–MS/MS-based steroid analysis is not straightforward, and understanding the chemical and analytical processes involved is essential for implementation of a robust clinical service. This article discusses specific challenges in the measurement of endogenous steroids using LC–MS/MS, and provides examples of the benefits it offers.