Use of Nonhuman Sera as a Highly Cost-Effective Internal Standard for Quantitation of Multiple Human Proteins Using Species-Specific Tryptic Peptides: Applicability in Clinical LC-MS Analyses.

Quantitation of proteins using liquid chromatography-tandem mass spectrometry (LC-MS/MS) is complex, with a multiplicity of options ranging from label-free techniques to chemically and metabolically labeling proteins. Increasingly, for clinically relevant analyses, stable isotope-labeled (SIL) internal standards (ISs) represent the "gold standard" for quantitation due to their similar physiochemical properties to the analyte, wide availability, and ability to multiplex to several peptides. However, the purchase of SIL-ISs is a resource-intensive step in terms of cost and time, particularly for screening putative biomarker panels of hundreds of proteins.

Effect of Recombinant Human Parathyroid Hormone (1-84) on Resolution of Active Charcot Neuro-osteoarthropathy in Diabetes: A Randomized, Double-Blind, Placebo-Controlled Study.

Objective: Fractures in Charcot neuro-osteoarthropathy (CN) often fail to heal despite prolonged immobilization with below-knee casting. The aim of the study was to assess the efficacy of recombinant human parathyroid hormone (PTH) in reducing time to resolution of CN and healing of fractures.

Research Design And Methods: People with diabetes and acute (active) Charcot foot were randomized (double-blind) to either full-length PTH (1-84) or placebo therapy, both in addition to below-knee casting and calcium and vitamin D3 supplementation.

Analytical considerations for the biochemical assessment of vitamin D status.

The most widely used and clinically accepted biochemical marker for assessing vitamin D status is the total serum 25-hydroxyvitamin D [25(OH)D] concentration. Despite the analysis of 25(OH)D dating back to the early 1970s, modern analytical techniques still exhibit significant interassay variability due to varying concentrations of other related vitamin D metabolites and sample-to-sample matrix differences. It is important for clinicians requesting 25(OH)D analyses to understand these issues and limitations, and where necessary to confront laboratories for details of analytical methods used.

LC-MS candidate reference methods for the harmonisation of parathyroid hormone (PTH) measurement: a review of recent developments and future considerations.

The analysis of intact parathyroid hormone (PTH) (PTH1-84) is useful in the diagnosis of hyper- and hypocalcaemia, hyperparathyroidism, and in the prevention of bone mineral disorders in renal patients. The analysis is complicated by the presence of PTH fragments, which may accumulate in renal failure and cross-react in immunoassays, including the most recent third-generation immunoassays. Large variability exists between different commercially available assays.

An automated, high-throughput method for targeted quantification of intact insulin and its therapeutic analogs in human serum or plasma coupling mass spectrometric immunoassay with high resolution and accurate mass detection (MSIA-HR/AM).

The detection and quantification of insulin and its therapeutic analogs is important for medical, sports doping, and forensic applications. Synthetic variants contain slight sequence variations to affect bioavailability. To reduce sample handling bias, a universal extraction method is required for simultaneous extraction of endogenous and variant insulins with subsequent targeted quantification by LC-MS.

Variability in the analysis of 25-hydroxyvitamin D by liquid chromatography-tandem mass spectrometry: the devil is in the detail.

Background: Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is increasingly used in clinical laboratories for the analysis of 25-hydroxyvitamin D (25OHD), but measurement is not straightforward. Importantly, LC-MS/MS is not a single technique: variables in sample preparation, chromatography and ionisation/fragmentation should each be considered.

Methods: We analysed results from a survey organised by the international Vitamin D External Quality Assessment Scheme (DEQAS), to determine the influence of such variables on the results for two DEQAS distributions.