Mass spectrometry for steroids, immunosuppressants, and other clinical applications

PresentationPresentation slides on matching mass spectrometry technology to clinical applications

Efficient Calculation of Accurate Masses of Isotopic Peaks

This paper presents a new method for calculating accurate masses of isotopic peaks. It is based on breaking the calculation into a binary series of calculations. The molecule is built up by a series of such calculations. At each step the accurate masses are calculated as a probability weighted sum of the masses of the contributing peaks. The method is computationally efficient and accurate for both mass and relative abundance

Performance enhancement in the measurement of 5 endogenous steroids by LC-MS/MS combined with differential ion mobility spectrometry

pre-printBackground: Challenges for steroid analysis by LC-MS/MS include low ionization efficiency, endogenous isobars with similar fragmentation patterns and chromatographic retention. Differential ion mobility spectrometry (DMS) provides an additional degree of separation prior to MS/MS detection, and shows promise in improving specificity of analysis. We developed a sensitive and specific method for measurement of corticosterone, 11-deoxycortisol, 11-deoxycorticosterone, 17-hydroxyprogesterone and progesterone in human serum and plasma using an ABSciex 5500 mass spectrometer equipped with a differential ion mobility interface. Methods: 250 μL aliquots of serum were spiked with deuterated internal standards and extracted with MTBE. The samples were analyzed using positivemode electrospray LC-DMS-MS/MS. Themethod was validated and compared with immunoassays and LC-MS/MS methods of reference laboratories. Results: Inter and intra assay imprecision was b10%. Limits of quantification and detection in nmol/L were 0.18, 0.09 for corticosterone and 17-hydroxyprogesterone, 0.30, 0.16 for 11-deoxycortisol, 0.12, 0.06 for progesterone and 0.06, 0.03 for 11-deoxycorticosterone. Comparison for progesterone and 17-hydroxyprogesterone with immunoassay showed slopes of 0.97 and 1.0, intercepts of 0.16 and 0.10 and coefficients of determination (r2) of 0.92 and 0.97, respectively. Progesterone by immunoassay showed positive bias in samples measuring b3.18 nmol/L. Reference intervals for progesterone and 11-deoxycorticosterone in post-menopausal women were found to be b2.88 and b0.28 nmol/L respectively. Conclusions: We developed and validated an LC-DMS-MS/MS method for analysis of five endogenous steroids suitable for routine measurements in clinical diagnostic laboratories. Specificity gained with DMS allows reducing the complexity of sample preparation, decreasing LC run times and increasing speed of the analysis

Identification of Histoplasma-Specific Peptides in Human Urine

Histoplasmosis is a severe dimorphic fungus infection, which is often difficult to diagnose due to similarity in symptoms to other diseases and lack of specific diagnostic tests. Urine samples from histoplasma-antigen-positive patients and appropriate controls were prepared using various sample preparation strategies including immunoenrichment, ultrafiltration, high-abundant protein depletion, deglycosylation, reverse-phase fractions, and digest using various enzymes. Samples were then analyzed by nanospray tandem mass spectrometry. Accurate mass TOF scans underwent molecular feature extraction and statistical analysis for unique disease makers, and acquired MS/MS data were searched against known human and histoplasma proteins. In human urine, some 52 peptides from 37 Histoplasma proteins were identified with high confidence. This is the first report of identification of a large number of Histoplasma-specific peptides from immunoassay-positive patient samples using tandem mass spectrometry and bioinformatics techniques. These findings may lead to novel diagnostic markers for histoplasmosis in human urine

Altered adrenal and gonadal steroids biosynthesis in patients with burn injury

Peer reviewe

Relationship between serum testosterone and fracture risk in men: a comparison of RIA and LC-MS/MS

BACKGROUND: Serum testosterone can be measured byLC-MS/MS and RIA. We investigated whether the testosterone–fracture relationship was affected by the method of measurement. METHODS: We measured total testosterone (TT) by LCMS/MS (TTLC-MS/MS) and RIA (TTRIA) in serum samples collected from 602 men whose incident fractures had been continuously ascertained by x-ray reports from 1989 to 2010. We measured bone mineral density (BMD) by dual-energy x-ray absorptiometry. The association between TT and fracture risk was assessed by the Cox proportional hazards model, taking into account the effect of age and BMD. CONCLUSIONS: The concordance between LC-MS/MS and RIA in the measurement of serum TT was moderate. Moreover, the magnitude of association between testosterone and fracture risk in older men was largely unaffected by the method of measurement. © 2015 American Association for Clinical Chemistr

Miniature Toroidal Radio Frequency Ion Trap Mass Analyzer

A miniature ion trap mass analyzer is reported. The described analyzer is a 1/5-scale version of a previously reported toroidal radio frequency (rf) ion trap mass analyzer. The toroidal ion trap operates with maximum rf trapping voltages about 1 kVp-p or less; however despite the reduced dimensions, it retains roughly the same ion trapping capacity as conventional 3D quadrupole ion traps. The curved geometry provides for a compact mass analyzer. Unit-mass resolved mass spectra for n-butylbenzene, xenon, and naphthalene are reported and preliminary sensitivity data are shown for naphthalene. The expected linear mass scale with rf amplitude scan is obtained when scanned using a conventional mass-selective instability scan mode combined with resonance ejection

Perceived Stress at Work Is Associated with Lower Levels of DHEA-S

Abstract Background: It is known that long-term psychosocial stress may cause or contribute to different diseases and symptoms and accelerate aging. One of the consequences of prolonged psychosocial stress may be a negative effect on the levels of dehydroepiandrosterone (DHEA) and its sulphated metabolite dehydroepiandrosterone sulphate (DHEA-S)

Childhood socioeconomic position and objectively measured physical capability levels in adulthood: a systematic review and meta-analysis

<p><b>Background:</b> Grip strength, walking speed, chair rising and standing balance time are objective measures of physical capability that characterise current health and predict survival in older populations. Socioeconomic position (SEP) in childhood may influence the peak level of physical capability achieved in early adulthood, thereby affecting levels in later adulthood. We have undertaken a systematic review with meta-analyses to test the hypothesis that adverse childhood SEP is associated with lower levels of objectively measured physical capability in adulthood.</p> <p><b>Methods and Findings:</b> Relevant studies published by May 2010 were identified through literature searches using EMBASE and MEDLINE. Unpublished results were obtained from study investigators. Results were provided by all study investigators in a standard format and pooled using random-effects meta-analyses. 19 studies were included in the review. Total sample sizes in meta-analyses ranged from N = 17,215 for chair rise time to N = 1,061,855 for grip strength. Although heterogeneity was detected, there was consistent evidence in age adjusted models that lower childhood SEP was associated with modest reductions in physical capability levels in adulthood: comparing the lowest with the highest childhood SEP there was a reduction in grip strength of 0.13 standard deviations (95% CI: 0.06, 0.21), a reduction in mean walking speed of 0.07 m/s (0.05, 0.10), an increase in mean chair rise time of 6% (4%, 8%) and an odds ratio of an inability to balance for 5s of 1.26 (1.02, 1.55). Adjustment for the potential mediating factors, adult SEP and body size attenuated associations greatly. However, despite this attenuation, for walking speed and chair rise time, there was still evidence of moderate associations.</p> <p><b>Conclusions:</b> Policies targeting socioeconomic inequalities in childhood may have additional benefits in promoting the maintenance of independence in later life.</p&gt

Statistical distance as a measure of physiological dysregulation is largely robust to variation in its biomarker composition

Physiological dysregulation may underlie aging and many chronic diseases, but is chal-lenging to quantify because of the complexity of the underlying systems. Recently, we de-scribed a measure of physiological dysregulation, DM, that uses statistical distance to assess the degree to which an individual’s biomarker profile is normal versus aberrant. However, the sensitivity of DM to details of the calculation method has not yet been sys-tematically assessed. In particular, the number and choice of biomarkers and the defini-tion of the reference population (RP, the population used to define a “normal” profile) may be important. Here, we address this question by validating the method on 44 common clinical biomarkers from three longitudinal cohort studies and one cross-sectional survey. DMs calculated on different biomarker subsets show that while the signal of physiological dysregulation increases with the number of biomarkers included, the value of additional markers diminishes as more are added and inclusion of 10-15 is generally sufficient. As long as enough markers are included, individual markers have little effect on the final met-ric, and even DMs calculated from mutually exclusive groups of markers correlate with each other at r~0.4-0.5. We also used data subsets to generate thousands of combina-tions of study populations and RPs to address sensitivity to differences in age range, sex, race, data set, sample size, and their interactions. Results were largely consistent (but not identical) regardless of the choice of RP; however, the signal was generally clearer with a younger and healthier RP, and RPs too different from the study population per-formed poorly. Accordingly, biomarker and RP choice are not particularly important in most cases, but caution should be used across very different populations or for fine-scale analyses. Biologically, the lack of sensitivity to marker choice and better performance of younger, healthier RPs confirm an interpretation of DM physiological dysregulation and as an emergent property of a complex system