Biostatistics primer for the radiologist.

OBJECTIVE: The purpose of this article is to review the most common data analysis methods encountered in radiology-based studies. Initially, description of variable types and their corresponding summary measures are provided; subsequent discussion focuses on comparison of these summary measures between groups, with a particular emphasis on regression analysis. CONCLUSION: Knowledge of statistical applications is critical for radiologists to accurately evaluate the current literature and to conduct scientifically rigorous studies. Misapplication of statistical methods can lead to inappropriate conclusions and clinical recommendations.

Utilization of angiography and embolization for abdominopelvic trauma: 14 years' experience at a level I trauma center.

OBJECTIVE: The objective of our study was to evaluate the long-term trends in the use of angiography and embolization for abdominopelvic injuries. MATERIALS AND METHODS: Utilization rates for pelvic and abdominal angiography, arterial embolization, and CT were analyzed for trauma patients with pelvic fractures and liver and kidney injuries admitted to a level 1 trauma center from 1996 to 2010. Multivariable linear regression was used to evaluate trends in the use of angioembolization. RESULTS: A total of 9145 patients were admitted for abdominopelvic injuries during the study period. Pelvic angiography decreased annually by 5.0% (95% CI, -6.4% to -3.7%) from 1996 to 2002 and by 1.8% (-2.4% to -1.2%) from 2003 to 2010. Embolization rates for these patients varied from 49% in 1997 to 100% in 2010. Utilization of pelvic CT on the day of admission increased significantly during this period. Abdominal angiography for liver and kidney injuries decreased annually by 3.3% (95% CI, -4.8% to -1.8%) and 2.0% (-4.3% to 0.3%) between 1996 and 2002 and by 0.8% (95% CI, -1.4% to -0.1%) and 0.9% (-2.0% to 0.1%) from 2003 to 2010, respectively. Embolization rates ranged from 25% in 1999 to 100% in 2010 for liver injuries and from 0% in 1997 to 80% in 2002 for kidney injuries. Abdominal CT for liver and kidney injuries on the day of admission also increased. CONCLUSION: A significant decrease in angiography use for trauma patients with pelvic fractures, liver injuries, and kidney injuries from 1996 to 2010 and a trend toward increasing embolization rates among patients who underwent angiography were found. These findings reflect a declining role of angiography for diagnostic purposes and emphasize the importance of angiography as a means to embolization for management.

CT use in hospitalized pediatric trauma patients: 15-year trends in a level I pediatric and adult trauma center.

PURPOSE: To evaluate the 15-year trend in the use of computed tomography (CT) in hospitalized pediatric trauma patients admitted to Harborview Medical Center (HMC) from 1996 to 2010. MATERIALS AND METHODS: This Health Insurance Portability and Accountability Act-compliant retrospective study was approved by the institutional review board. The requirement for informed consent was waived. The HMC trauma registry was linked to the billing department data, and patient and injury-related characteristics were extracted, in addition to type and frequency of CT procedures. Patients discharged from the emergency department and patients hospitalized for less than 24 hours were not included in this study. Patients were classified into three categories according to age: 0-14 years, 15-18 years, and 19-54 years (reference group). Multivariate negative binomial regression was used to compare CT usage among different age groups by adjusting for patient sex, race and/or ethnicity, insurance status, mechanism of injury, injury severity, final disposition (dead vs alive), and year of admission. The trend for CT use in children and teenagers was also evaluated. RESULTS: A total of 64 425 trauma patients 0-54 years of age were admitted during the study period. Compared with CT usage in adults 19-54 years old, usage in children up to 15 years of age was significantly lower for spine (incidence rate ratio [IRR], 0.89; 95% confidence interval [CI]: 0.85, 0.92), maxillofacial (IRR, 0.89; 95% CI: 0.81, 0.97), and thoracic (IRR, 0.91; 95% CI: 0.84, 0.99) CT. Increased use of head CT was observed in children up to 15 years old (IRR, 1.09; 95% CI: 1.05, 1.13) and 15-18 years old (IRR, 1.08; 95% CI: 1.04, 1.13). From 2008 to 2010, usage rates in children up to 15 years old and 15-18 years old was relatively unchanged or slightly decreased for almost all CT types. CONCLUSION: A decreasing or unchanged trend was observed in CT usage in hospitalized pediatric trauma patients in recent years. © RSNA, 2013.

Accuracy of Medical Student Measurements of CT Right-to-Left Ventricular Diameter in Patients with Acute Pulmonary Embolism.

Objectives: Acute pulmonary embolism (PE) is a common disease, necessitating risk stratification to determine management. A right ventricle (RV) to left ventricle (LV) diameter ratio ≥1.0 on computed tomography pulmonary angiography (CTPA) suggests RV strain, which may indicate a worse prognosis. Two prior studies showed that residents with brief training by a radiologist could accurately measure RV/LV ratio. We assessed whether medical students could accurately measure RV dilatation. Methods: We conducted a post hoc analysis of a retrospective cohort study of adults undergoing management for acute PE at 21 community emergency departments across Kaiser Permanente Northern California from 2013 to 2015. We created a sample, stratified to contain an equal number of patients from each of the 5 PE Severity Index classes. Four medical students measured RV and LV diameter on CTPA after training from an emergency medicine physician and an interventional radiologist. We used Cohen's kappa statistics, Bland-Altman plots, and Pearson correlation coefficients to assess interrater reliability. Results: Of the 108 CTPAs reviewed, 79 (73%) showed RV dilatation and 29 (27%) did not. The kappa statistic for the presence of RV dilatation of the medical students compared to the radiologist showed moderate agreement for 3 medical students (kappa (95% CI): 0.46 (0.21-0.70), 0.49 (0.31-0.68), 0.50 (0.32-0.68)) and fair agreement for 1 medical student (kappa (95% CI): 0.29 (0.10-0.47)). The average interrater differences in RV/LV ratio between a radiologist and each of the 4 medical students were -0.04, -0.05, 0.04, and 0.24. Pearson correlation coefficients were 0.87, 0.80, 0.74, and 0.78, respectively, indicating moderate correlation (P < .001 for all). Conclusion: Medical students were able to identify RV dilatation on CTPA in moderate agreement with that of a radiologist. Further study is needed to determine whether medical student accuracy could improve with additional training.

Computational Modeling of the Liver Arterial Blood Flow for Microsphere Therapy: Effect of Boundary Conditions.

Transarterial embolization is a minimally invasive treatment for advanced liver cancer using microspheres loaded with a chemotherapeutic drug or radioactive yttrium-90 (90Y) that are injected into the hepatic arterial tree through a catheter. For personalized treatment, the microsphere distribution in the liver should be optimized through the injection volume and location. Computational fluid dynamics (CFD) simulations of the blood flow in the hepatic artery can help estimate this distribution if carefully parameterized. An important aspect is the choice of the boundary conditions imposed at the inlet and outlets of the computational domain. In this study, the effect of boundary conditions on the hepatic arterial tree hemodynamics was investigated. The outlet boundary conditions were modeled with three-element Windkessel circuits, representative of the downstream vasculature resistance. Results demonstrated that the downstream vasculature resistance affected the hepatic artery hemodynamics such as the velocity field, the pressure field and the blood flow streamline trajectories. Moreover, the number of microspheres received by the tumor significantly changed (more than 10% of the total injected microspheres) with downstream resistance variations. These findings suggest that patient-specific boundary conditions should be used in order to achieve a more accurate drug distribution estimation with CFD in transarterial embolization treatment planning.

Correlates of protective behavior utilization among heavy-drinking college students.

Previous studies have suggested that college students who use protective strategies while drinking are at a lower risk for drinking-related consequences. This study evaluated the correlates of protective behavior utilization in a group of 281 heavy-drinking college students. Students who reported heavier drinking were less likely to use protective behaviors, even after adjusting for covariates. Male gender and perceived history of parental alcohol abuse also predicted lower protective behavior score. The most frequently endorsed strategies among females were "Knowing where your drink has been at all times" and "Going home with a friend," whereas the most frequently endorsed strategies among males were "Knowing where your drink has been at all times" and "Using a designated driver." For females, the factor structure of the protective behaviors measure was consistent with previous studies; however, for males, the results suggest a four-factor solution. Findings are discussed in terms of their implications on future research and prevention programming.

Childhood trauma fatality and resource allocation in injury control programs in a developing country.

BACKGROUND: Only a few studies have addressed the trimodal distribution of childhood trauma fatalities in lesser developed countries. We conducted this study to evaluate pre-hospital, Emergency Department (ED) and in-hospital distribution of childhood injury-related death for each mechanism of injury in Tehran, Iran. This information will be used for the efficient allocation of the limited injury control resources in the city. METHODS: We used Tehran's Legal Medicine Organization (LMO) database. This is the largest and the most complete database that receives information about trauma fatalities from more than 100 small and large hospitals in Tehran. We reviewed all the medical records and legal documents of the deceased registered in LMO from September 1999 to September 2000. Demographic and injury related characteristics of the children 15 years old or younger were extracted from the records. RESULTS: Ten percent of the 4,233 trauma deaths registered in LMO occurred among children 15 years old or younger. Motor vehicle crashes (MVCs) (50%), burns (18%), falls (6%) and poisonings (6%) were the most common mechanisms of unintentional fatal injuries. Prehospital, emergency department and hospital deaths comprised 42%, 20% and 37% of the trauma fatalities, respectively. While, more than 80% of fatal injuries due to poisoning and drowning occurred in prehospital setting, 92% of burn-related fatalities happened after hospital admission. CONCLUSION: Injury prevention is the single most important solution for controlling trauma fatalities due to poisoning and drowning. Improvements in the quality of care in hospitals and intensive care units might substantially alleviate the magnitude of the problem due to burns. Improvements in prehospital and ED care might significantly decrease MVC and falls-related fatalities.

An evaluation of the association between vehicle type and the source and severity of pedestrian injuries.

To evaluate the effect of vehicle type (passenger vehicle vs. light truck vehicle) on crash trajectory and on the consequent source and severity of pedestrian injury, we analyzed data from the Pedestrian Crash Data Study (PCDS), conducted by National Highway Traffic Safety Administration (NHTSA) from 1994 to 1998. While 62% of the adults in PV (passenger vehicle)-related crashes were carried by the vehicle, such pedestrian-vehicle interaction was observed only in 28% of LTV (light truck vehicle)-adult crashes. Being thrown forward or knocked down were the most common (65%) type of pedestrian-vehicle interactions for LTV-adult crashes. For children, 93% of those struck by LTVs and 46% of those struck by PVs were thrown forward or knocked down. For adults, LTVs were more likely than PVs to cause thorax (37% vs. 20%) and abdomen injuries (33% vs. 18%). For children, LTVs were more likely than PVs to cause injuries to the upper extremity (71% vs. 56%) and abdomen (14% vs. 8%). For adults struck by PVs the most common sources of injury were windshield for head injuries (63%), hood surface for thorax (67%), abdomen (58%), spine (30%), and upper extremity (36%) injuries, and bumper for the lower extremity injuries (60%). The leading causes of injury for adult-LTV crashes were ground for head (39%) and upper extremity (37%) injuries, hood edge for thorax (48%) and abdomen (56%) injuries, hood surface for spine injuries (36%), and bumper for lower extremity injuries (45%). For child-PV crashes, ground was the most common source of face (37%) abdomen (83%), spine (43%), and upper extremity injuries (54%). For children hit by LTVs, 52% of face, 67% of abdomen, 100% of spine, and 60% of upper extremity injuries were attributed to ground contacts. Altogether, the major sources of injury were hood surface and windshield for PV-pedestrian crashes and hood surface and hood edge for LTV-pedestrian crashes. Changes in design, such as altering the geometry and stiffness of front-end structures, might be associated with considerable decrease in the frequency and severity of pedestrian injury.

Child and adult pedestrian impact: the influence of vehicle type on injury severity.

In the United States, the vehicle fleet is shifting from predominantly passenger cars (automobiles) to SUVs, light trucks, and vans (LTV). This study investigates how pedestrian severe injury and mortality are associated with vehicle type and pedestrian age. The Pedestrian Crash Data Study (PCDS) database for years 1994-1998 was used for a cross-sectional study design. Outcome measures were Injury Severity Score, Maximum Abbreviated Injury Score, Abbreviated Injury Scale, Pedestrian Mortality, Functional Capacity Index and Life Years Lost to Injury. Compared to children, adult pedestrians were more likely to sustain severe injury (OR = 2.81; 95% CI: 1.56-5.06) or mortality (OR = 2.91; 95% CI: 1.10-7.74) when examining all vehicle types. However, after adjusting for vehicle type and impact speed, this association was not statistically significant at p < 0.05. Compared to passenger cars, pedestrians struck by LTV were more likely to have severe injuries (OR = 1.31; 95% CI: 0.88-1.94) or mortality (OR = 1.40; 95% CI: 0.84-2.34) for all pedestrians. Adjusting for pedestrian age, this association was more obvious and significant at lower impact speeds ( < or = 30 km/h); odds ratios of severe injury and mortality were 3.34 (p< 0.01) and 1.87 (p= 0.07), respectively. Adults hit by LTV had the highest risk of injury and mortality. These findings indicate that pedestrian age, vehicle engineering design and impact speed are highly contributing to risks of pedestrian injury and mortality.

Outcomes and resource utilization associated with underage drinking at a level I trauma center.

PURPOSE: To examine the association of blood alcohol content (BAC) on hospital-based outcomes and imaging utilization for patients <21 years admitted to a level I trauma center. METHODS: Retrospective analysis of alcohol-involved injuries in patients 13-20 years, admitted to a level I trauma center from 1996 to 2010. An injury was considered alcohol involved if the patient had a BAC > 0. Multivariable logistic regression was used to compare mortality, discharge destination (home and skilled nursing facility), intensive care unit admission, and operating room use between patients with and without positive BAC for patients 13-15, 16-17, and 18-20 years. Multivariable linear regression was used to compare length of hospitalization. Finally, multivariable negative binomial regression evaluated radiology resource utilization (x-ray, computed tomography [CT], and magnetic resonance imaging). RESULTS: A total of 7,663 patients, 13-20 years old, were admitted over the study period. A positive BAC was reported in 19% of these patients. In general, the presence of alcohol was not associated with mortality rate, length of hospitalization, intensive care unit, and operating room use or discharge status for any age group. However, the presence of alcohol was associated with higher utilization of head (incidence rate ratio [IRR] 1.13, 95% confidence interval [CI] 1.02-1.26), cervical spine (IRR 1.10, 95% CI 1.01-1.22), and thoracic (IRR 1.30, 95% CI 1.05-1.63) CTs in young adults 18-20 years. No differences in CT use were observed in patients 13-15 or 16-17 years. CONCLUSIONS: Positive BAC was not significantly associated with adverse outcomes or resource utilization in younger trauma patients. However, the use of certain body region CTs was associated with positive BAC in patients 18-20 years.

Effect of an image-sharing network on CT utilization for transferred trauma patients: a 5-year experience at a level I trauma center.

PURPOSE: The aim of this study was to evaluate the influence of an image-sharing network established between referring hospitals and a level I trauma center on CT utilization at the trauma center. METHODS: This retrospective study was approved by the local institutional review board. The requirement for informed consent was waived. Harborview Medical Center's trauma registry was linked to billing department data, and detailed information on all resources utilized during each patient's hospitalization was obtained. Negative binomial regression was used to evaluate body region-specific CT utilization between direct-admit and transfer patients after adjustment for potential confounding variables. Special attention was paid to 2005 as the year internet-based image sharing between Harborview Medical Center and referring hospitals was established. RESULTS: A total of 81,159 trauma patients were admitted to Harborview Medical Center (44% transfers) during the study period. The utilization of head CT slightly increased from 1996 to 2005, with no significant difference between direct-admit and transfer patients. Between 2005 and 2010, utilization remained relatively unchanged; however, significantly higher utilization rates were observed for direct-admit patients. A relatively similar pattern was observed for pelvic CT; however, between 2005 and 2010, CT use was greater for direct-admit compared with transfer patients. Abdominal and thoracic CT was relatively unchanged between 2005 and 2010. However, both studies had significantly higher utilization rates for direct-admit patients. CONCLUSIONS: The utilization rates of CT of different body regions have been higher for direct-admit trauma patients compared with transfer patients since 2005; however, decreasing utilization trends have been observed in recent years.

Declining trend in the use of repeat computed tomography for trauma patients admitted to a level I trauma center for traffic-related injuries.

OBJECTIVE: To evaluate the trend in utilization of repeat (i.e. ≥2) computed tomography (CT) and to compare utilization patterns across body regions for trauma patients admitted to a level I trauma center for traffic-related injuries (TRI). MATERIALS AND METHODS: We linked the Harborview Medical Center trauma registry (1996-2010) to the billing department data. We extracted the following variables: type and frequency of CTs performed, age, gender, race/ethnicity, insurance status, injury mechanism and severity, length of hospitalization, intensive care unit (ICU) admission and final disposition. TRIs were defined as motor vehicle collisions, motorcycle, bicycle and pedestrian-related injuries. Logistic regression was used to evaluate the association between utilization of different body region repeat (i.e. ≥2) CTs and year of admission, adjusting for patient and injury-related characteristics that could influence utilization patterns. RESULTS: A total of 28,431 patients were admitted for TRIs over the study period and 9499 (33%) received repeat CTs. From 1996 to 2010, the proportion of patients receiving repeat CTs decreased by 33%. Relative to 2000 and adjusting for other covariates, patients with TRIs admitted in 2010 had significantly lower odds of undergoing repeat head (OR=0.61; 95% CI: 0.49-0.76), pelvis (OR=0.37; 95% CI: 0.27-0.52), cervical spine (OR=0.23; 95% CI: 0.12-0.43), and maxillofacial CTs (OR=0.24; 95% CI: 0.10-0.57). However, they had higher odds of receiving repeat thoracic CTs (OR=1.86; 95% CI: 1.02-3.38). CONCLUSION: A significant decrease in the utilization of repeat CTs was observed in trauma patients presenting with traffic-related injuries over a 15-year period.

Correlates of dating violence among male and female heavy-drinking college students.

OBJECTIVE: To evaluate the correlates for dating violence among heavy-drinking college students. METHOD: Participants were at least 18 years old and reported at least one heavy-drinking episode in the past 2 weeks. RESULTS: After covariate adjustment, estimated peak blood alcohol concentration during the past month was associated with higher victims' verbal-emotional abuse score, and perpetrators' verbal-emotional abuse and threatening abuse scores ( N = 280). In addition, being non-White was significantly associated with higher victims' threatening abuse, physical abuse, and total abuse scores and perpetrators' threatening abuse and physical abuse scores. Moreover, male students had significantly lower victims' threatening abuse and physical abuse scores and perpetrators' threatening abuse scores compared to female students. DISCUSSION: Preventive programs that target dating violence among heavy-drinking college students should consider alcohol use as an important risk factor for abusive behaviors, both for the victims as well as the perpetrators.

Prehospital trauma care: what do we really know?

PURPOSE OF REVIEW: The prehospital care of injured patients has been surrounded with much controversy over the years. This controversy exists regarding the specific interventions used on-scene and en-route to definitive care centers, regarding the overall approach to the care of these patients (advanced life support versus basic life support) and with regards to who should be providing this care. This section of the journal aims to review the most current literature concerning these topics as well as highlight some important and relevant literature preceding it. RECENT FINDINGS: Studies examining overall prehospital care in terms of morbidity, mortality and cost have been published over the last year and important points from these studies are highlighted in the text. Unfortunately, there have not been any recent, appropriately powered, prospective studies that help in clarifying this controversy. An international study of prehospital care has recently been completed and is summarized. Recent studies looking at specific aspects of prehospital care (endotracheal intubation, intravenous access and therapy, rural trauma) are also outlined in the text. SUMMARY: There is no convincing evidence that prehospital advanced life support in the urban setting provides any benefit to injured patients in terms of either morbidity or mortality.

International comparison of prehospital trauma care systems.

OBJECTIVE: Given the recent emphasis on developing prehospital trauma care globally, we embarked upon a multicentre study to compare trauma patients' outcome within and between countries with technician-operated advanced life support (ALS) and physician-operated (Doc-ALS) emergency medical service (EMS) systems. These environments represent the continuum of prehospital care in high income countries with more advanced prehospital trauma care systems. METHODS: Five countries with ALS-EMS system and four countries with Doc-ALS EMS system provided us with de-identified patient-level data from their national or local trauma registries. Generalised linear latent and mixed models was used in order to compare emergency department (ED) shock rate (systolic blood pressure (SBP) <90mmHg) and early trauma fatality rate (i.e. death during the first 24h after hospital arrival) between ALS and Doc-ALS EMS systems. Logistic regression was used to compare outcomes of interest among different countries, accounting for within-system correlation in patient outcomes. RESULTS: After adjustment for patient age, sex, type and mechanism of injury, injury severity score and SBP at scene, the ED shock rate did not vary significantly between Doc-ALS and ALS systems (OR: 1.16, 95% CI: 0.73-1.91). However, the early trauma fatality rate was significantly lower in Doc-ALS EMS systems compared with ALS EMS systems (OR: 0.70, 95% CI: 0.54-0.91). Furthermore, we found a considerable heterogeneity in patient outcomes among countries even with similar type of EMS systems. CONCLUSION: These findings suggest that prehospital trauma care systems that dispatch a physician to the scene may be associated with lower early trauma fatality rates, but not necessarily with significantly better outcomes on other clinical measures. The reasons for these findings deserve further studies.

Emergency Medical Service (EMS) systems in developed and developing countries.

OBJECTIVES: To compare patient- and injury-related characteristics of trauma victims and pre-hospital trauma care systems among different developed and developing countries. METHOD: We collated de-identified patient-level data from national or local trauma registries in Australia, Austria, Canada, Greece, Germany, Iran, Mexico, New Zealand, the Netherlands, the United Kingdom and the United States. Patient and injury-related characteristics of trauma victims with injury severity score (ISS) >15 and the pre-hospital trauma care provided to these patients were compared among different countries. RESULTS: A total of 30,339 subjects from one or several regions in 11 countries were included in this analysis. Austria (51%), Germany (41%) and Australia (30%) reported the highest proportion of air ambulance use. Monterrey, Mexico (median 10.1min) and Montreal, Canada (median 16.1min) reported the shortest and Germany (median: 30min) and Austria (median: 26min) reported the longest scene time. Use of intravenous fluid therapy among advanced EMS systems without physicians as pre-hospital care providers, varied from 30% (in the Netherlands) to 55% (in the US). The corresponding percentages in advanced EMS systems with physicians actively involved in pre-hospital trauma care, excluding Montreal in Canada, ranged from 63% (in London, in the UK) to 75% in Germany and Austria. Austria and Germany also reported the highest percentage of pre-hospital intubation (61% and 56%, respectively). CONCLUSION: This study provides an early look at international variability in patient mix, process of care, and performance of different pre-hospital trauma care systems worldwide. International efforts should be devoted to developing a minimum standard data set for trauma patients.

The acute medical care costs of fall-related injuries among the U.S. older adults.

OBJECTIVES: Falls in the older adults are a major public health concern. The growing population of adults 65 years or older, advances in medical care and changes in the costs of care motivated our study of the acute health care costs of fall-related injuries among the older adults in the United States of America. DESIGN AND SETTINGS: The Market Scan Medicare Supplemental database 1998 was used to estimate reimbursed costs for hospital, emergency department (ED), and outpatient clinic treatments for unintentional falls among older adults. RESULTS: A fall on the same level due to slipping, tripping, or stumbling was the most common mechanism of injury (28%). Mean hospitalisation cost was 17,483 US dollars(S.D.: 22,426 US dollars) in 2004 US dollars. Femur fracture was the most expensive type of injury (18,638 US dollars, S.D.: 19,990 US dollars). The mean reimbursement cost of an ED visit was 236 US dollars and 412 US dollars for an outpatient clinic visit. CONCLUSION: The magnitude of the economic and social costs of falls in older adults underscores the need for active research in the field of falls prevention.