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Diagnostic criteria for major depressive disorder allow for heterogeneous symptom profiles but genetic analysis of major depressive symptoms has the potential to identify clinical and etiological subtypes. There are several challenges to integrating symptom data from genetically informative cohorts, such as sample size differences between clinical and community cohorts and various patterns of missing data.
Methods
We conducted genome-wide association studies of major depressive symptoms in three cohorts that were enriched for participants with a diagnosis of depression (Psychiatric Genomics Consortium, Australian Genetics of Depression Study, Generation Scotland) and three community cohorts who were not recruited on the basis of diagnosis (Avon Longitudinal Study of Parents and Children, Estonian Biobank, and UK Biobank). We fit a series of confirmatory factor models with factors that accounted for how symptom data was sampled and then compared alternative models with different symptom factors.
Results
The best fitting model had a distinct factor for Appetite/Weight symptoms and an additional measurement factor that accounted for the skip-structure in community cohorts (use of Depression and Anhedonia as gating symptoms).
Conclusion
The results show the importance of assessing the directionality of symptoms (such as hypersomnia versus insomnia) and of accounting for study and measurement design when meta-analyzing genetic association data.
Mössbauer spectra of 9 glauconite samples from Upper Cretaceous and Lower Tertiary strata in the South Island of New Zealand contain a broad shoulder due to low intensity absorption continuous between 1.0 and 2.5 mm/sec when the absorber is at room temperature; the shoulder is absent, and sharp peaks are apparent in spectra taken with the absorber at 80°K. The data suggest that electron transfer occurs between adjacent Fe3+ and Fe2+ ions at room temperature. The low temperature spectra indicate that all Fe in the glauconites is in octahedral coordination. Fe3+ and Fe2+ ions occur in both eis and trans sites; Fe3+ shows a strong preference for eis sites whereas Fe2+ shows an even stronger preference for trans sites.
The partially variable oxidation state of Fe in glauconite is interpreted in terms of a geochemical model for glauconitization of a degraded or incomplete progenitor phyllosilicate. The model involves exchange of Fe2+ for other cations which temporarily stabilize the progenitor, followed by Fe2+-Fe3+ charge transfer reactions. Each reaction results from the system's tendency towards equilibrium. The model is supported by the observation that artificially leached glauconite increases both its Fe3+ and its Fe2+ content when placed in a solution containing Fe2+ as the only Fe ion present.
Many clinical trials leverage real-world data. Typically, these data are manually abstracted from electronic health records (EHRs) and entered into electronic case report forms (CRFs), a time and labor-intensive process that is also error-prone and may miss information. Automated transfer of data from EHRs to eCRFs has the potential to reduce data abstraction and entry burden as well as improve data quality and safety.
Methods:
We conducted a test of automated EHR-to-CRF data transfer for 40 participants in a clinical trial of hospitalized COVID-19 patients. We determined which coordinator-entered data could be automated from the EHR (coverage), and the frequency with which the values from the automated EHR feed and values entered by study personnel for the actual study matched exactly (concordance).
Results:
The automated EHR feed populated 10,081/11,952 (84%) coordinator-completed values. For fields where both the automation and study personnel provided data, the values matched exactly 89% of the time. Highest concordance was for daily lab results (94%), which also required the most personnel resources (30 minutes per participant). In a detailed analysis of 196 instances where personnel and automation entered values differed, both a study coordinator and a data analyst agreed that 152 (78%) instances were a result of data entry error.
Conclusions:
An automated EHR feed has the potential to significantly decrease study personnel effort while improving the accuracy of CRF data.
We present WALLABY pilot data release 1, the first public release of H i pilot survey data from the Wide-field ASKAP L-band Legacy All-sky Blind Survey (WALLABY) on the Australian Square Kilometre Array Pathfinder. Phase 1 of the WALLABY pilot survey targeted three
$60\,\mathrm{deg}^{2}$
regions on the sky in the direction of the Hydra and Norma galaxy clusters and the NGC 4636 galaxy group, covering the redshift range of
$z \lesssim 0.08$
. The source catalogue, images and spectra of nearly 600 extragalactic H i detections and kinematic models for 109 spatially resolved galaxies are available. As the pilot survey targeted regions containing nearby group and cluster environments, the median redshift of the sample of
$z \approx 0.014$
is relatively low compared to the full WALLABY survey. The median galaxy H i mass is
$2.3 \times 10^{9}\,{\rm M}_{{\odot}}$
. The target noise level of
$1.6\,\mathrm{mJy}$
per 30′′ beam and
$18.5\,\mathrm{kHz}$
channel translates into a
$5 \sigma$
H i mass sensitivity for point sources of about
$5.2 \times 10^{8} \, (D_{\rm L} / \mathrm{100\,Mpc})^{2} \, {\rm M}_{{\odot}}$
across 50 spectral channels (
${\approx} 200\,\mathrm{km \, s}^{-1}$
) and a
$5 \sigma$
H i column density sensitivity of about
$8.6 \times 10^{19} \, (1 + z)^{4}\,\mathrm{cm}^{-2}$
across 5 channels (
${\approx} 20\,\mathrm{km \, s}^{-1}$
) for emission filling the 30′′ beam. As expected for a pilot survey, several technical issues and artefacts are still affecting the data quality. Most notably, there are systematic flux errors of up to several 10% caused by uncertainties about the exact size and shape of each of the primary beams as well as the presence of sidelobes due to the finite deconvolution threshold. In addition, artefacts such as residual continuum emission and bandpass ripples have affected some of the data. The pilot survey has been highly successful in uncovering such technical problems, most of which are expected to be addressed and rectified before the start of the full WALLABY survey.
We present the most sensitive and detailed view of the neutral hydrogen (
${\rm H\small I}$
) emission associated with the Small Magellanic Cloud (SMC), through the combination of data from the Australian Square Kilometre Array Pathfinder (ASKAP) and Parkes (Murriyang), as part of the Galactic Australian Square Kilometre Array Pathfinder (GASKAP) pilot survey. These GASKAP-HI pilot observations, for the first time, reveal
${\rm H\small I}$
in the SMC on similar physical scales as other important tracers of the interstellar medium, such as molecular gas and dust. The resultant image cube possesses an rms noise level of 1.1 K (
$1.6\,\mathrm{mJy\ beam}^{-1}$
)
$\mathrm{per}\ 0.98\,\mathrm{km\ s}^{-1}$
spectral channel with an angular resolution of
$30^{\prime\prime}$
(
${\sim}10\,\mathrm{pc}$
). We discuss the calibration scheme and the custom imaging pipeline that utilises a joint deconvolution approach, efficiently distributed across a computing cluster, to accurately recover the emission extending across the entire
${\sim}25\,\mathrm{deg}^2$
field-of-view. We provide an overview of the data products and characterise several aspects including the noise properties as a function of angular resolution and the represented spatial scales by deriving the global transfer function over the full spectral range. A preliminary spatial power spectrum analysis on individual spectral channels reveals that the power law nature of the density distribution extends down to scales of 10 pc. We highlight the scientific potential of these data by comparing the properties of an outflowing high-velocity cloud with previous ASKAP+Parkes
${\rm H\small I}$
test observations.
We present the data and initial results from the first pilot survey of the Evolutionary Map of the Universe (EMU), observed at 944 MHz with the Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The survey covers
$270 \,\mathrm{deg}^2$
of an area covered by the Dark Energy Survey, reaching a depth of 25–30
$\mu\mathrm{Jy\ beam}^{-1}$
rms at a spatial resolution of
$\sim$
11–18 arcsec, resulting in a catalogue of
$\sim$
220 000 sources, of which
$\sim$
180 000 are single-component sources. Here we present the catalogue of single-component sources, together with (where available) optical and infrared cross-identifications, classifications, and redshifts. This survey explores a new region of parameter space compared to previous surveys. Specifically, the EMU Pilot Survey has a high density of sources, and also a high sensitivity to low surface brightness emission. These properties result in the detection of types of sources that were rarely seen in or absent from previous surveys. We present some of these new results here.
The first demonstration of laser action in ruby was made in 1960 by T. H. Maiman of Hughes Research Laboratories, USA. Many laboratories worldwide began the search for lasers using different materials, operating at different wavelengths. In the UK, academia, industry and the central laboratories took up the challenge from the earliest days to develop these systems for a broad range of applications. This historical review looks at the contribution the UK has made to the advancement of the technology, the development of systems and components and their exploitation over the last 60 years.
We reviewed the sustainability of a multifaceted intervention on catheter-associated urinary tract infection (CAUTI) in 3 intensive care units. During the 4-year postintervention period, we observed reductions in urine culture rates (from 80.9 to 47.5 per 1,000 patient days; P < .01), catheter utilization (from 0.68 to 0.58; P < .01), and CAUTI incidence rates (from 1.7 to 0.8 per 1,000 patient days; P = .16).
Emergency Medical Services (EMS) systems have developed protocols for prehospital activation of the cardiac catheterization laboratory for patients with suspected ST-elevation myocardial infarction (STEMI) to decrease first-medical-contact-to-balloon time (FMC2B). The rate of “false positive” prehospital activations is high. In order to decrease this rate and expedite care for patients with true STEMI, the American Heart Association (AHA; Dallas, Texas USA) developed the Mission Lifeline PreAct STEMI algorithm, which was implemented in Los Angeles County (LAC; California USA) in 2015. The hypothesis of this study was that implementation of the PreAct algorithm would increase the positive predictive value (PPV) of prehospital activation.
Methods:
This is an observational pre-/post-study of the effect of the implementation of the PreAct algorithm for patients with suspected STEMI transported to one of five STEMI Receiving Centers (SRCs) within the LAC Regional System. The primary outcome was the PPV of cardiac catheterization laboratory activation for percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG). The secondary outcome was FMC2B.
Results:
A total of 1,877 patients were analyzed for the primary outcome in the pre-intervention period and 405 patients in the post-intervention period. There was an overall decrease in cardiac catheterization laboratory activations, from 67% in the pre-intervention period to 49% in the post-intervention period (95% CI for the difference, -14% to -22%). The overall rate of cardiac catheterization declined in post-intervention period as compared the pre-intervention period, from 34% to 30% (95% CI, for the difference -7.6% to 0.4%), but actually increased for subjects who had activation (48% versus 58%; 95% CI, 4.6%-15.0%). Implementation of the PreAct algorithm was associated with an increase in the PPV of activation for PCI or CABG from 37.9% to 48.6%. The overall odds ratio (OR) associated with the intervention was 1.4 (95% CI, 1.1-1.8). The effect of the intervention was to decrease variability between medical centers. There was no associated change in average FMC2B.
Conclusions:
The implementation of the PreAct algorithm in the LAC EMS system was associated with an overall increase in the PPV of cardiac catheterization laboratory activation.
Introduction: Determining fluid status prior to resuscitation provides a more accurate guide for appropriate fluid administration in the setting of undifferentiated hypotension. Emergency Department (ED) point of care ultrasound (PoCUS) has been proposed as a potential non-invasive, rapid, repeatable investigation to ascertain inferior vena cava (IVC) characteristics. Our goal was to determine the feasibility of using PoCUS to measure IVC size and collapsibility. Methods: This was a planned secondary analysis of data from a prospective multicentre international study investigating PoCUS in ED patients with undifferentiated hypotension. We prospectively collected data on IVC size and collapsibility using a standard data collection form in 6 centres. The primary outcome was the proportion of patients with a clinically useful (determinate) scan defined as a clearly visible intrahepatic IVC, measurable for size and collapse. Descriptive statistics are provided. Results: A total of 138 scans were attempted on 138 patients; 45.7% were women and the median age was 58 years old. Overall, one hundred twenty-nine scans (93.5%; 95% CI 87.9 to 96.7%) were determinate. 131 (94.9%; 89.7 to 97.7%) were determinate for IVC size, and 131 (94.9%; 89.7 to 97.7%) were determinate for collapsibility. Conclusion: In this analysis of 138 ED patients with undifferentiated hypotension, the vast majority of PoCUS scans to investigate IVC characteristics were determinate. Future work should include analysis of the value of IVC size and collapsibility in determining fluid status in this group.
Introduction: Patients presenting to the emergency department (ED) with hypotension have a high mortality rate and require careful yet rapid resuscitation. The use of cardiac point of care ultrasound (PoCUS) in the ED has progressed beyond the basic indications of detecting pericardial fluid and activity in cardiac arrest. We examine if finding left ventricular dysfunction (LVD) on emergency physician performed PoCUS reliably predicts the presence of cardiogenic shock in hypotensive ED patients. Methods: We prospectively collected PoCUS findings performed in 135 ED patients with undifferentiated hypotension as part of an international study. Patients with clearly identified etiologies for hypotension were excluded, along with other specific presumptive diagnoses. LVD was defined as identification of a generally hypodynamic LV in the setting of shock. PoCUS findings were collected using a standardized protocol and data collection form. All scans were performed by PoCUS-trained emergency physicians. Final shock type was defined as cardiogenic or non-cardiogenic by independent specialist blinded chart review. Results: All 135 patients had complete follow up. Median age was 56 years, 53% of patients were male. Disease prevalence for cardiogenic shock was 12% and the mortality rate was 24%. The presence of LVD on PoCUS had a sensitivity of 62.50% (95%CI 35.43% to 84.80%), specificity of 94.12% (88.26% to 97.60%), positive-LR 10.62 (4.71 to 23.95), negative-LR 0.40 (0.21 to 0.75) and accuracy of 90.37% (84.10% to 94.77%) for detecting cardiogenic shock. Conclusion: Detecting left ventricular dysfunction on PoCUS in the ED may be useful in confirming the underlying shock type as cardiogenic in otherwise undifferentiated hypotensive patients.
Early detection and indicated early intervention in the initial prodromal phase should considerably improve the course of psychoses. Yet, the benefits of such programmes still require an evidence-based evaluation on the basis of a sufficient sample-size.
Objective
This report presents an overview on the concept and design of the European Prediction of Psychosis Study (EPOS) an European 4-country naturalistic field-study of the initial Prodrome.
Materials and Methods
Across six participating centres (Germany: Cologne, Berlin; Finland: Turku; The Netherlands: Amsterdam; United Kingdom: Birmingham, Manchester), 16 to 40 year old putatively prodromal persons attending specialized services or general psychiatric services underwent multi-level baseline, 9-months follow-up, and 18-months follow-up examinations. Inclusion criteria were the presence of APS, BLIPS, at least 2 of 9 Basic Symptoms (BS), and Familial Risk or Schizotypal Personality Disorder plus Reduced Functioning (FR+RF). In addition, psychopathological, neurocognitive, neurobiological, psychosocial, and service and treatment-related assessments were carried out.
Results
A substantial part of more than 250 subjects included into the study participated in their respective baseline, 1st follow-up, and 2nd follow-up examinations. A high percentage presented themselves with BS and/or APS, a smaller percentage with BLIPS or FR+RF. The rates of transition into psychosis and the levels of psychopathology, distress and functional decline found among this patient group underline the need for indicated early recognition and intervention.
Conclusions
EPOS provides for the first time a sound data base allowing an evaluation of the applicability and cost-benefit ratio of early detection and intervention programmes in Europe.
A main objective of EPOS is to provide a valid multifactorial model for the prediction of psychosis. One major element of such a model should be the clinical state.
Methods
In a European multicentre study, persons fulfilling clinical criteria thought to indicate an increased risk for psychosis (PAR) were assessed amongst others with different psychopathological instruments covering the whole spectrum from basic symptoms to frank psychotic symptoms. Inclusion criteria comprised attenuated positive symptoms (APS), brief limited intermittent psychotic symptoms (BLIPS), cognitive basic symptoms (CogDis) and a combination of family risk and reduced functioning (S&T).
Results
246 PAR were included into the study, mostly by APS or CogDis. Analysis of demographical data showed a high amount of functional impairment, resulting e.g. in low mean GAF scores (51.0 ± 11.8 SD), and of non-psychotic axis-I disorders. In September 2006, the hazard rate for a conversion to psychosis was 15.3 at 12 and 20.0 at 18 months after baseline assessment. According to the inclusion criteria, the highest rate of conversion was observed among PAR with BLIPS. On a dimensional level, a low GAF score was among the best predictors of conversion.
Conclusions
The transition rates of EPOS were in line with recent studies. A first analysis of clinical data supports the notion that the functional state should be an inherent part of any set of clinical risk criteria. Further analysis will consider the contribution of single symptoms or symptom combinations and the impact of symptom duration.
The aim of this presentation is to summarize the results of the published systematic reviews / meta-analyses of the randomized controlled trials that have investigated the effectiveness of medications for the treatment of obsessive compulsive disorder (OCD) in children/adolescents and adults and to present preliminary results from a new review study using network meta-analytical techniques
Methods
Medline, Cochrane database, and the register of controlled trials maintained by the Cochrane Collaboration Depression, Anxiety & Neurosis Group (CCDAN) were searched for relevant trials, systematic reviews and/or meta-analyses.
Results
Regarding the new review study we were able to extract 103 pharmacological arms (preliminary results: 9 for Fluoxetine, 16 for Fluvoxamine, 11 for Paroxetine, 10 for Sertraline, 16 for Clomipramine, 7 for Citalopram / escitalopram, 2 for Venlafaxine, and 32 for Placebo) with a total number of 6572 patients randomized. The previous meta-analyses have confirmed the efficacy for all SSRIs and Clomipramine in all age groups while for other drugs further evidence is required. In the context of this presentation preliminary results of the relative efficacy of each drug, using network meta-analysis techniques will also be reported.
Conclusions
Several antidepressants have established their efficacy and acceptability for the management of non-resistant OCD. The major weakness of the literature so far is that head to head comparisons between antidepressants are few and therefore it is difficult to establish a clear hierarchy of the efficacy and acceptability of the various agents. This gap in the present literature will be filled by the present review.
Night-migratory songbirds appear to sense the direction of the Earth's magnetic field via radical pair intermediates formed photochemically in cryptochrome flavoproteins contained in photoreceptor cells in their retinas. It is an open question whether this light-dependent mechanism could be sufficiently sensitive given the low-light levels experienced by nocturnal migrants. The scarcity of available photons results in significant uncertainty in the signal generated by the magnetoreceptors distributed around the retina. Here we use results from Information Theory to obtain a lower bound estimate of the precision with which a bird could orient itself using only geomagnetic cues. Our approach bypasses the current lack of knowledge about magnetic signal transduction and processing in vivo by computing the best-case compass precision under conditions where photons are in short supply. We use this method to assess the performance of three plausible cryptochrome-derived flavin-containing radical pairs as potential magnetoreceptors.
Background: Biallelic variants in POLR1C are associated with POLR3-related leukodystrophy (POLR3-HLD), or 4H leukodystrophy (Hypomyelination, Hypodontia, Hypogonadotropic Hypogonadism), and Treacher Collins syndrome (TCS). The clinical spectrum of POLR3-HLD caused by variants in this gene has not been described. Methods: A cross-sectional observational study involving 25 centers worldwide was conducted between 2016 and 2018. The clinical, radiologic and molecular features of 23 unreported and previously reported cases of POLR3-HLD caused by POLR1C variants were reviewed. Results: Most participants presented between birth and age 6 years with motor difficulties. Neurological deterioration was seen during childhood, suggesting a more severe phenotype than previously described. The dental, ocular and endocrine features often seen in POLR3-HLD were not invariably present. Five patients (22%) had a combination of hypomyelinating leukodystrophy and abnormal craniofacial development, including one individual with clear TCS features. Several cases did not exhibit all the typical radiologic characteristics of POLR3-HLD. A total of 29 different pathogenic variants in POLR1C were identified, including 13 new disease-causing variants. Conclusions: Based on the largest cohort of patients to date, these results suggest novel characteristics of POLR1C-related disorder, with a spectrum of clinical involvement characterized by hypomyelinating leukodystrophy with or without abnormal craniofacial development reminiscent of TCS.
Introduction: Although use of point of care ultrasound (PoCUS) protocols for patients with undifferentiated hypotension in the Emergency Department (ED) is widespread, our previously reported SHoC-ED study showed no clear survival or length of stay benefit for patients assessed with PoCUS. In this analysis, we examine if the use of PoCUS changed fluid administration and rates of other emergency interventions between patients with different shock types. The primary comparison was between cardiogenic and non-cardiogenic shock types. Methods: A post-hoc analysis was completed on the database from an RCT of 273 patients who presented to the ED with undifferentiated hypotension (SBP <100 or shock index > 1) and who had been randomized to receive standard care with or without PoCUS in 6 centres in Canada and South Africa. PoCUS-trained physicians performed scans after initial assessment. Shock categories and diagnoses recorded at 60 minutes after ED presentation, were used to allocate patients into subcategories of shock for analysis of treatment. We analyzed actual care delivered including initial IV fluid bolus volumes (mL), rates of inotrope use and major procedures. Standard statistical tests were employed. Sample size was powered at 0.80 (α:0.05) for a moderate difference. Results: Although there were expected differences in the mean fluid bolus volume between patients with non-cardiogenic and cardiogenic shock, there was no difference in fluid bolus volume between the control and PoCUS groups (non-cardiogenic control 1878 mL (95% CI 1550 – 2206 mL) vs. non-cardiogenic PoCUS 1687 mL (1458 – 1916 mL); and cardiogenic control 768 mL (194 – 1341 mL) vs. cardiogenic PoCUS 981 mL (341 – 1620 mL). Likewise there were no differences in rates of inotrope administration, or major procedures for any of the subcategories of shock between the control group and PoCUS group patients. The most common subcategory of shock was distributive. Conclusion: Despite differences in care delivered by subcategory of shock, we did not find any significant difference in actual care delivered between patients who were examined using PoCUS and those who were not. This may help to explain the previously reported lack of outcome difference between groups.
Introduction: Point of care ultrasound has been reported to improve diagnosis in non-traumatic hypotensive ED patients. We compared diagnostic performance of physicians with and without PoCUS in undifferentiated hypotensive patients as part of an international prospective randomized controlled study. The primary outcome was diagnostic performance of PoCUS for cardiogenic vs. non-cardiogenic shock. Methods: SHoC-ED recruited hypotensive patients (SBP < 100 mmHg or shock index > 1) in 6 centres in Canada and South Africa. We describe previously unreported secondary outcomes relating to diagnostic accuracy. Patients were randomized to standard clinical assessment (No PoCUS) or PoCUS groups. PoCUS-trained physicians performed scans after initial assessment. Demographics, clinical details and findings were collected prospectively. Initial and secondary diagnoses including shock category were recorded at 0 and 60 minutes. Final diagnosis was determined by independent blinded chart review. Standard statistical tests were employed. Sample size was powered at 0.80 (α:0.05) for a moderate difference. Results: 273 patients were enrolled with follow-up for primary outcome completed for 270. Baseline demographics and perceived category of shock were similar between groups. 11% of patients were determined to have cardiogenic shock. PoCUS had a sensitivity of 80.0% (95% CI 54.8 to 93.0%), specificity 95.5% (90.0 to 98.1%), LR+ve 17.9 (7.34 to 43.8), LR-ve 0.21 (0.08 to 0.58), Diagnostic OR 85.6 (18.2 to 403.6) and accuracy 93.7% (88.0 to 97.2%) for cardiogenic shock. Standard assessment without PoCUS had a sensitivity of 91.7% (64.6 to 98.5%), specificity 93.8% (87.8 to 97.0%), LR+ve 14.8 (7.1 to 30.9), LR- of 0.09 (0.01 to 0.58), Diagnostic OR 166.6 (18.7 to 1481) and accuracy of 93.6% (87.8 to 97.2%). There was no significant difference in sensitivity (-11.7% (-37.8 to 18.3%)) or specificity (1.73% (-4.67 to 8.29%)). Diagnostic performance was also similar between other shock subcategories. Conclusion: As reported in other studies, PoCUS based assessment performed well diagnostically in undifferentiated hypotensive patients, especially as a rule-in test. However performance was similar to standard (non-PoCUS) assessment, which was excellent in this study.
Measuring diet choice in grazing animals is challenging, complicating the assessment of feed efficiency in pasture-based systems. Furthermore, animals may modify their intake of a forage species depending on its nutritive value and on their own physiological status. Various fecal markers have been used to estimate feed intake in grazing animals. However, plant-wax markers such as n-alkanes (ALK) and long-chain alcohols may provide reliable estimates of both dietary choices and intakes. Still, their use in beef cattle has been relatively limited. The present study was designed to test the reliability of the ALK technique to estimate diet choices in beef heifers. Twenty-two Angus-cross heifers were evaluated at both post-weaning and yearling age. At each age, they were offered both red clover and fescue hay as cubes. Following 3-week acclimation periods, daily intake of each forage species was assessed daily for 10 days. During the final 5 days, fecal grab samples were collected twice daily. The ALK fecal concentrations were adjusted using recovery fractions compiled from literature. Diet composition was estimated using two statistical methods. Post-weaning, dietary choices were reliably estimated, with low residual error, regardless of the statistical approach adopted. The regression of observed on estimated red clover proportion ranged from 0.85±0.08 to 1.01±0.09 for fecal samples collected in the p.m. and for daily proportions once averaged, respectively. However, at yearling age, the estimates were less reliable. There was a tendency to overestimate the red clover proportion in diets of heifers preferring fescue, and vice versa. This was due to greater variability in ALK fecal concentrations in the yearling heifers. Overall, the ALK technique provided a reliable tool for estimating diet choice in animals fed a simple forage diet. Although further refinements in the application of this methodology are needed, plant-wax markers provide opportunities for evaluating diet composition in grazing systems in cattle.