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An interlaboratory comparison study was conducted by the Vitamin D Standardization Program (VDSP) to assess the performance of liquid chromatography – tandem mass spectrometry (LC-MS/MS) assays used for the determination of serum total 25-hydroxyvitamin D (25(OH)D), which is the sum of 25-hydroxyvitamin D2 (25(OH)D2) and 25-hydroxyvitamin D3 (25(OH)D3). A set of 50 single-donor samples was assigned target values for concentrations of 25(OH)D2, 25(OH)D3, 3-epi-25-hydroxyvitamin D3 (3-epi-25(OH)D3), and 24R,25-dihydroxyvitamin D3 (24R,25(OH)2D3) using isotope dilution liquid chromatography – tandem mass spectrometry (ID LC-MS/MS). VDSP Intercomparison Study 2 Part 1 includes results from 14 laboratories using 14 custom LC-MS/MS assays. Assay performance was evaluated using mean % bias compared to the assigned target values and using linear regression analysis of the test assay mean results and the target values. Only 53% of the LC-MS/MS assays met the VDSP criterion of mean % bias ≤ |±5%|. For the LC-MS/MS assays not meeting the ≤ |±5%| criterion, four assays had mean % bias of between 12 and 21%. Based on multivariable regression analysis using the concentrations of the four individual vitamin D metabolites in the 50 single-donor samples, the performance of several LC-MS/MS assays was found to be influenced by the presence of 3-epi-25(OH)D3. The results of this interlaboratory study represent the most comprehensive comparison of LC-MS/MS assay performance for serum total 25(OH)D and document the significant impact of the lack of separation of 3-epi-25(OH)D3 and 25(OH)D3 on assay performance, particularly with regard to mean % bias.

Objective Biochemical assessment is recommended for patients prior to initiating and following a ketogenic diet (KD). There is no published literature regarding current practice in the UK and Ireland. We aimed to explore practice in comparison with international guidelines, determine approximate costs of biochemical testing in KD patients across the UK and Ireland, and promote greater consistency in KD services nationally. Methods A survey was designed to determine the biochemical tests requested for patients at baseline, 3, 6, 12, 18, and 24 months + on KD. The survey was circulated to 39 centers across the UK and Ireland. Results Sixteen centers completed the survey. Full blood count, electrolytes, calcium, liver function tests (LFTs), lipid profile, and vitamin D were requested at all centers at baseline, in keeping with international guidelines. Bicarbonate, total protein, and urinalysis were less consistently requested. Magnesium and zinc were requested by all centers, despite not being specifically recommended for pre‐diet evaluation in guidelines. Urea and electrolyte profiles and some LFTs were consistently requested at follow‐up, in accordance with guidelines. Other LFTs and renal tests, full blood count, lipid profile, acylcarnitine profile, selenium, vitamin D, and urinalysis were less consistently requested at follow‐up. The mean costs of the lowest and highest number of tests requested at baseline in our participating centers were £167.54 and £501.93; the mean costs of the lowest and highest number of tests requested at 3‐month follow‐up were £19.17 and £450.06. Significance Biochemical monitoring of KD patients varies widely across the UK and Ireland and does not fully correspond to international best practice guidelines. With an ongoing drive for cost‐effectiveness within health care, further work is needed to streamline practice while ensuring patient safety.

An interlaboratory study was conducted through the Vitamin D Standardization Program (VDSP) to assess commutability of Standard Reference Materials® (SRMs) and proficiency testing/external quality assessment (PT/EQA) samples for determination of serum total 25-hydroxyvitamin D [25(OH)D] using ligand binding assays and liquid chromatography-tandem mass spectrometry (LC-MS/MS). A set of 50 single-donor serum samples were assigned target values for 25-hydroxyvitamin D2 [25(OH)D2] and 25-hydroxyvitamin D3 [25(OH)D3] using reference measurement procedures (RMPs). SRM and PT/EQA samples evaluated included SRM 972a (four levels), SRM 2973, six College of American Pathologists (CAP) Accuracy-Based Vitamin D (ABVD) samples, and nine Vitamin D External Quality Assessment Scheme (DEQAS) samples. Results were received from 28 different laboratories using 20 ligand binding assays and 14 LC-MS/MS methods. Using the test assay results for total serum 25(OH)D (i.e., the sum of 25(OH)D2 and 25(OH)D3) determined for the single-donor samples and the RMP target values, the linear regression and 95% prediction intervals (PIs) were calculated. Using a subset of 42 samples that had concentrations of 25(OH)D2 below 30 nmol/L, one or more of the SRM and PT/EQA samples with high concentrations of 25(OH)D2 were deemed non-commutable using 5 of 11 unique ligand binding assays. SRM 972a (level 4), which has high exogenous concentration of 3-epi-25(OH)D3, was deemed non-commutable for 50% of the LC-MS/MS assays.

The Vitamin D External Quality Assessment Scheme (DEQAS) distributes human serum samples four times per year to over 1000 participants worldwide for the determination of total serum 25-hydroxyvitamin D [25(OH)D)]. These samples are stored at −40 °C prior to distribution and the participants are instructed to store the samples frozen at −20 °C or lower after receipt; however, the samples are shipped to participants at ambient conditions (i.e., no temperature control). To address the question of whether shipment at ambient conditions is sufficient for reliable performance of various 25(OH)D assays, the equivalence of DEQAS human serum samples shipped under frozen and ambient conditions was assessed. As part of a Vitamin D Standardization Program (VDSP) commutability study, two sets of the same nine DEQAS samples were shipped to participants at ambient temperature and frozen on dry ice. Twenty-eight laboratories participated in this study and provided 34 sets of results for the measurement of 25(OH)D using 20 ligand binding assays and 14 liquid chromatography–tandem mass spectrometry (LC–MS/MS) methods. Equivalence of the assay response for the frozen versus ambient DEQAS samples for each assay was evaluated using multi-level modeling, paired t-tests including a false discovery rate (FDR) approach, and ordinary least squares linear regression analysis of frozen versus ambient results. Using the paired t-test and confirmed by FDR testing, differences in the results for the ambient and frozen samples were found to be statistically significant at p < 0.05 for four assays (DiaSorin, DIAsource, Siemens, and SNIBE prototype). For all 14 LC–MS/MS assays, the differences in the results for the ambient- and frozen-shipped samples were not found to be significant at p < 0.05 indicating that these analytes were stable during shipment at ambient conditions. Even though assay results have been shown to vary considerably among different 25(OH)D assays in other studies, the results of this study also indicate that sample handling/transport conditions may influence 25(OH)D assay response for several assays.

BackgroundA subnormal cortisol response (30 min level (C30min)<550 nmol/L) to synthetic adrenocorticotrophic hormone/Synacthen test (SDST) in all infants does not necessarily indicate underlying or persistent hypothalamic–pituitary–adrenal axis pathology.MethodsWe retrospectively evaluated the diagnoses and outcomes in 68 infants who had a SDST at age <6 months from 2011 to 2014.Results29 (43%) infants had a subnormal SDST. Causative pathology was identified in 9/29 (31%). In 20/29 (69%) with no identified pathology, repeat SDST was normal in 18/20 (90%) at median age 0.6 (range 0.1–3.2) years but persistently subnormal in 2. Those with a transient abnormality were more likely to be small for gestational age (P=0.03) and had higher initial SDST C30min (390 nmol/L vs 181 nmol/L, P=0.01) than those with pathology.ConclusionSpecific aetiology can be identified in a third of infants with a subnormal SDST. When the aetiology remains elusive, adrenal function should be reassessed as the problem can be transient.

1. In order to determine the influence of habitat shape on aspects of the population dynamics of birds, 196 male red-capped robins Petroica goodenovii were surveyed using song playback in large non-linear woodland remnants and linear roadside remnants in the wheatbelt of south-eastern Australia. 2. The average density of male robins was significantly higher in large non-linear remnants [0.86 ± 0.09 (SD) birds ha-1] than in small linear remnants [0.35 ± 0.16 (SD) birds ha-1]. 3. Red-capped robins exhibit delayed plumage maturation, and 14% of the males captured were yearlings. This percentage was significantly higher in roadside remnants (20%) than in large, non-linear remnants (8%). 4. These results indicate that different population processes are occurring in the individual remnants and the dynamics of the metapopulation are potentially complex. 5. Land managers must not focus excessively on wildlife corridors (narrow, linear habitats) at the expense of appropriate management and restoration of large areas of native vegetation.

Artificial nests monitored with automatically triggered cameras were used to determine the intensity of nest predation and the identity of nest predators in linear remnants and large remnants of woodland in the wheatbelt of New South Wales, Australia. Nests were constructed from wire, grass, and bark to mimic those of the Red-capped Robin (Petroica goodenovii) and were stocked with eggs made from modelling clay. The incidence of predation was significantly higher in linear remnants (62% predation) than in large remnants (34%). Forty-seven independent photographic events were recorded, and nine species of bird accounted for all predation. Two species of predator, the Grey Shrike-thrush (Colluricincla harmonica) and the Grey Butcherbird (Cracticus torquatus), were responsible for 70% of predation and were detected at nests in both linear and large remnants. The remaining seven species of predator were detected only at nests in linear remnants. Bird surveys conducted in the same sites revealed that of the species of predator identified from photographs all, with two exceptions, were present in both linear remnants and large remnants. However, the abundance of identified predators was significantly higher in linear remnants. This study suggests that linear strips of vegetation, despite providing habitat in which birds can live, or a conduit through which they can move, may have limited value as breeding habitat. The current enthusiasm for protection and creation of corridors should not be at the expense of restoration and sympathetic management of large areas of native vegetation.

Artificial nests monitored with automatically triggered cameras were used to determine the intensity of nest predation and the identity of nest predators in linear remnants and large remnants of woodland in the wheatbelt of New South Wales, Australia. Nests were constructed from wire, grass, and bark to mimic those of the Red-capped Robin (Petroica goodenovii) and were stocked with eggs made from modelling clay. The incidence of predation was significantly higher in linear remnants (62% predation) than in large remnants (34%). Forty-seven independent photographic events were recorded, and nine species of bird accounted for all predation. Two species of predator, the Grey Shrike-thrush (Colluricincla harmonica) and the Grey Butcherbird (Cracticus torquatus), were responsible for 70% of predation and were detected at nests in both linear and large remnants. The remaining seven species of predator were detected only at nests in linear remnants. Bird surveys conducted in the same sites revealed that of the species of predator identified from photographs all, with two exceptions, were present in both linear remnants and large remnants. However, the abundance of identified predators was significantly higher in linear remnants. This study suggests that linear strips of vegetation, despite providing habitat in which birds can live, or a conduit through wich they can move, may have limited value as breeding habitat. The current enthusiasm for protection and creation of corridors should not be at the expense of restoration and sympathetic management of large areas of native vegetation. /// Se usaron nidos artificiales monitoreados con cámaras de control automático para determinar la intensidad de la depredación de los nidos y la identidad de los depredadores en remanentes lineares y en grandes parcelas remanentes en el \"cinto de trigo\" de la Nueva Gales del Sur en Australia. Los nidos se construyeron de alambres, hierbas y corteza para imitar los de Petroica goodenovvii y se apertrecharon con huevos hechos de plastilina. La incidencia de depredación fué significativamente grande en remanentes lineares (62% depredados) que en las grandes parcelas remanentes (34%). Cuarentisiete eventos independientes se registraron fotográficamente y se documentó que hay nueve especies de aves depredadoras. Dos especies depredadoras, Colluricincla harmonica y Cracticus torquatus, fueron responsables del 70% de la depredación y se detectaron en tanto en nidos en remanentes lineares como en remanentes grandes. Las otras siete especies depredadoras se detectaron solamente en remanentes lineares. Muestreos de aves conducidos en los mismos lugares revelaron que las especies depredadoras identificadas por fotografías, con dos excepciones, estaban presentes tanto en remanentes lineares como en remanentes grandes. Sin embargo, la abundancia de depredadores identificados fué significativamente mayor en remanentes lineares. Este estudio sugiere que parcelas lineares de vegetación, además de proveer habitat en el cual las aves pueden vivir, o un conducto a través del cual se puede mover, pueden tener valor limitado como habitat reproductivo. El entusiasmo actual para la protección y creación de corredores no debiera ser al costo de la restauración y del manejo sensible de áreas grandes de vegetación nativa.