Did COVID-19 Change Emergency Department Admissions?

OBJECTIVE: This study aimed to describe the impact of the coronavirus disease (COVID-19) pandemic on emergency department (ED) admissions for urgent diagnoses. METHODS: From January 1, 2019, until December 31, 2020, patients older than 18 years who attended the ED at University Hospital of Leuven (UZ Leuven, Belgium) were included. Urgent diagnoses selected in the First Hour Quintet were collected. The periods of the pandemic waves in 2020 were analyzed and compared with the same time period in 2019. RESULTS: During the first wave of the pandemic, 16 075 patients attended the ED compared with 16 893 patients during the comparison period in 2019. The proportion of patients having one of the diagnoses of the First Hour Quintet was similar between the periods (4.4% vs 4.5%). During the second wave, 14 739 patients attended the ED compared with 18 704 patients during the same period in 2019; 5.6% of patients had a diagnosis of the First Hour Quintet compared with 4.3% of patients in the comparison period. CONCLUSION: This study showed a decrease in the number of patients attending the ED during the COVID-19 pandemic. Further studies are needed to determine for which conditions patients visited the ED less.

Elimination testing with adapted scoring reduces guessing and anxiety in multiple-choice assessments, but does not increase grade average in comparison with negative marking.

BACKGROUND AND HYPOTHESES: This study is the first to offer an in-depth comparison of elimination testing with the scoring rule of Arnold & Arnold (hereafter referred to as elimination testing with adapted scoring) and negative marking. As such, this study is motivated by the search for an alternative for negative marking that still discourages guessing, but is less disadvantageous for non-relevant student characteristics such a risk-aversion and does not result in grade inflation. The comparison is structured around seven hypotheses: in comparison with negative marking, elimination testing with adapted scoring leads to (1) a similar average score (no grade inflation); (2) students expressing their partial knowledge; (3) a decrease in the number of blank answers; (4) no gender bias in the number of blank answers; (5) a reduction in guessing; (6) a decrease in self-reported test anxiety; and finally (7) students preferring elimination testing with adapted scoring over negative marking. METHODOLOGY: To investigate the above hypotheses, this study implemented elimination testing with adapted scoring and negative marking in real exam settings in two courses in a Faculty of Medicine at a large university. Due to changes in the master of medicine the same two courses were taught to both students of the 1st and 2nd master in the same semester. Given that both student groups could take the same exam with different test instructions and scoring methods, a unique opportunity occurred in which elimination testing with adapted scoring and negative marking could be compared in a high-stakes testing situation. After receiving the grades on the exams, students received a questionnaire to assess their experiences. FINDINGS: The statistical analysis taking into account student ability and gender showed that elimination testing with adapted scoring is a valuable alternative for negative marking when looking for a scoring method that discourages guessing. In contrast to traditional scoring of elimination testing, elimination testing with adapted scoring does not result in grade inflation in comparison with negative marking. This study showed that elimination testing with adapted scoring reduces blank answers and finds strong indications for the reduction of guessing in comparison with negative marking. Finally, students preferred elimination testing with adapted scoring over negative marking and reported lower stress levels in elimination testing with adapted scoring in comparison with negative marking.

From histology to micro-CT: Measuring and modeling resorption cavities and their relation to bone competence.

The process of bone remodelling plays an essential role in the emergence and maintenance of bone geometry and its internal structure. Osteoclasts are one of the three main bone cell types that play a crucial role in the bone remodelling cycle. At the microstructural level, osteoclasts create bone deficits by eroding resorption cavities. Understanding how these cavities impair the mechanical quality of the bone is not only relevant in quantifying the impact of resorption cavities in healthy bone and normal aging, but maybe even more so in quantifying their role in metabolic bone diseases. Metabolic bone diseases and their treatment are both known to affect the bone remodelling cycle; hence, the bone mechanical competence can and will be affected. However, the current knowledge of the precise dimensions of these cavities and their effect on bone competence is rather limited. This is not surprising considering the difficulties in deriving three-dimensional (3D) properties from two-dimensional (2D) histological sections. The measurement difficulties are reflected in the evaluation of how resorption cavities affect bone competence. Although detailed 3D models are generally being used to quantify the mechanical impact of the cavities, the representation of the cavities themselves has basically been limited to simplified shapes and averaged cavity properties. Qualitatively, these models indicate that cavity size and location are important, and that the effect of cavities is larger than can be expected from simple bone loss. In summary, the dimensions of osteoclast resorption cavities were until recently estimated from 2D measures; hence, a careful interpretation of resorption cavity dimensions is necessary. More effort needs to go into correctly quantifying resorption cavities using modern 3D imaging techniques like micro-computed tomography (micro-CT) and synchrotron radiation CT. Osteoclast resorption cavities affect bone competence. The structure-function relationships have been analysed using computational models that, on one hand, provide rather detailed information on trabecular bone structure, but on the other incorporate rather crude assumptions on cavity dimensions. The use of high-resolution representations and parametric descriptions could be potential routes to improve the quantitative fidelity of these models.

The effect of resorption cavities on bone stiffness is site dependent.

Resorption cavities formed during the bone remodelling cycle change the structure and thus the mechanical properties of trabecular bone. We tested the hypotheses that bone stiffness loss due to resorption cavities depends on anatomical location, and that for identical eroded bone volumes, cavities would cause more stiffness loss than homogeneous erosion. For this purpose, we used beam-shell finite element models. This new approach was validated against voxel-based FE models. We found an excellent agreement for the elastic stiffness behaviour of individual trabeculae in axial compression (R(2) = 1.00) and in bending (R(2)>0.98), as well as for entire trabecular bone samples to which resorption cavities were digitally added (R(2) = 0.96, RMSE = 5.2%). After validation, this new method was used to model discrete cavities, with dimensions taken from a statistical distribution, on a dataset of 120 trabecular bone samples from three anatomical sites (4th lumbar vertebra, femoral head, iliac crest). Resorption cavities led to significant reductions in bone stiffness. The largest stiffness loss was found for samples from the 4th lumbar vertebra, the lowest for femoral head samples. For all anatomical sites, resorption cavities caused significantly more stiffness loss than homogeneous erosion did. This novel technique can be used further to evaluate the impact of resorption cavities, which are known to change in several metabolic bone diseases and due to treatment, on bone competence.

Glucocorticoid-induced changes in the geometry of osteoclast resorption cavities affect trabecular bone stiffness.

Bone fracture risk can increase through bone microstructural changes observed in bone pathologies, such as glucocorticoid-induced osteoporosis. Resorption cavities present one of these microstructural aspects. We recently found that glucocorticoids (GCs) affect the shape of the resorption cavities. Specifically, we found that in the presence of GC osteoclasts (OCs) cultured on bone slices make more trenchlike cavities, compared to rather round cavities in the absence of GCs, while the total eroded surface remained constant. For this study, we hypothesized that trenchlike cavities affect bone strength differently compared to round cavities. To test this hypothesis, we cultured OCs on bone slices in the presence and absence of GC and quantified their dimensions. These data were used to model the effects of OC resorption cavities on bone mechanical properties using a validated beam-shell finite element model of trabecular bone. We demonstrated that a change in the geometry of resorption cavities is sufficient to affect bone competence. After correcting for the increased EV/BV with GCs, the difference to the control condition was no longer significant, indicating that the GC-induced increase in EV/BV, which is closely related to the shape of the cavities, highly determines the stiffness effect. The lumbar spine was the anatomic site most affected by the GC-induced changes on the shape of the cavities. These findings might explain the clinical observation that the prevalence of vertebral fractures during GC treatment increases more than hip, forearm and other nonvertebral fractures.

Fast and accurate specimen-specific simulation of trabecular bone elastic modulus using novel beam-shell finite element models.

Elastic modulus and strength of trabecular bone are negatively affected by osteoporosis and other metabolic bone diseases. Micro-computed tomography-based beam models have been presented as a fast and accurate way to determine bone competence. However, these models are not accurate for trabecular bone specimens with a high number of plate-like trabeculae. Therefore, the aim of this study was to improve this promising methodology by representing plate-like trabeculae in a way that better reflects their mechanical behavior. Using an optimized skeletonization and meshing algorithm, voxel-based models of trabecular bone samples were simplified into a complex structure of rods and plates. Rod-like and plate-like trabeculae were modeled as beam and shell elements, respectively, using local histomorphometric characteristics. To validate our model, apparent elastic modulus was determined from simulated uniaxial elastic compression of 257 cubic samples of trabecular bone (4mm×4mm×4mm; 30µm voxel size; BIOMED I project) in three orthogonal directions using the beam-shell models and using large-scale voxel models that served as the gold standard. Excellent agreement (R(2)=0.97) was found between the two, with an average CPU-time reduction factor of 49 for the beam-shell models. In contrast to earlier skeleton-based beam models, the novel beam-shell models predicted elastic modulus values equally well for structures from different skeletal sites. It allows performing detailed parametric analyses that cover the entire spectrum of trabecular bone microstructures.

The correlation between the SOS in trabecular bone and stiffness and density studied by finite-element analysis.

For the clinical assessment of osteoporosis (i.e., a degenerative bone disease associated with increased fracture risk), ultrasound has been proposed as an alternative or supplement to the dual-energy X-ray absorptiometry (DEXA) technique. However, the interaction of ultrasound waves with (trabecular) bone remains relatively poorly understood. The present study aimed to improve this understanding by simulating ultrasound wave propagation in 15 trabecular bone samples from the human lumbar spine, using microcomputed tomography-based finite-element modeling. The model included only the solid bone, without the bone marrow. Two structural parameters were calculated: the bone volume fraction (BV/TV) and the structural (apparent) elastic modulus (E(s)), and the ultrasound propagation parameter speed of sound (SOS). Relations between BV/TV and E(s) were similar to published experimental relations. At 1 MHz, correlations between SOS and the structural parameters BV/TV and Es were rather weak, but the results can be explained from the specific features of the trabecular structure and the intrinsic material elastic modulus E(i). In particular, the systematic differences between the three main directions provide information on the trabecular structure. In addition, at 1 MHz the correlation found between the simulated SOS values and those calculated from the simple bar equation was poor when the three directions are considered separately. Hence, under these conditions, the homogenization approach-including the bar equation-is not valid. However, at lower frequencies (50-300 kHz) this correlation significantly improved. It is concluded that detailed analysis of ultrasound wave propagation through the solid structure in various directions and with various frequencies, can yield much information on the structural and mechanical properties of trabecular bone.