Pilot task-based assessment of noise levels among firefighters

Purpose

Over one million American firefighters are routinely exposed to various occupational hazards. While efforts have been made to identify and reduce some causes of injuries and illnesses among firefighters, relatively little has been done to evaluate and understand occupational noise exposures in this group. The purpose of this pilot study was to apply a task-based noise exposure assessment methodology to firefighting operations to evaluate potential noise exposure sources, and to use collected task-based noise levels to create noise exposure estimates for evaluation of risk of noise-induced hearing loss by comparison to the 8-hr and 24-hr recommended exposure limits (RELs) for noise of 85 and 80.3 dBA, respectively.

Methods

Task-based noise exposures (n = 100 measurements) were measured in three different fire departments (a rural department in Southeast Michigan and suburban and urban departments in Northern California). These levels were then combined with time-at-task information collected from firefighters to estimate 8-hr noise exposures for the rural and suburban fire departments (n = 6 estimates for each department). Data from 24-hr dosimetry measurements and crude self-reported activity categories from the urban fire department (n = 4 measurements) were used to create 24-hr exposure estimates to evaluate the bias associated with the task-based estimates.

Results

Task-based noise levels were found to range from 82 to 109 dBA, with the highest levels resulting from use of saws and pneumatic chisels. Some short (e.g., 30 min) sequences of common tasks were found to result in nearly an entire allowable daily exposure. The majority of estimated 8-hr and 24-hr exposures exceeded the relevant recommended exposure limit. Predicted 24-hr exposures showed substantial imprecision in some cases, suggesting the need for increased task specificity and highlighting the variability of firefighting noise exposures.

Conclusions

The results indicate potential for overexposure to noise from a variety of firefighting tasks and equipment, and suggest a need for further exposure characterization and additional hearing loss prevention efforts.

Relevance to industry

Firefighters may be at risk of noise-induced hearing loss, which can affect their fitness for duty and ability to respond effectively to emergencies. The results of this study suggest that additional efforts at hearing loss prevention among firefighters are warranted.     

Costs of occupational musculoskeletal disorders (MSDs) in the United States

Background

For the years 1992–2010 musculoskeletal disorders (MSDs) accounted for 29–35% of all occupational injuries and illnesses involving days away from work in the United States (US) (AFL-CIO, 2012). According to the American Federation of Labor and Congress of Industrial Organizations (AFL-CIO) 2012 report ‘Death on the Job’, for the years 1992 through 2010 the percent of cases involving MSDs in private industry were highest in 2000 (35%) and lowest in 2007 (29%). In 2010, the median number of days away from work for MSDs was 11 compared to 8 for all occupational injury cases involving days away from work; the median number of days away from work for Carpal Tunnel Syndrome (CTS) was 25, more than three times as high as for all other BLS injuries involving days away from work (BLS, 2011). This study estimated the costs of work related MSDs, and given that the number of days lost due to CTS is very high, it also estimated the costs of CTS separately in the United States (US) for the years 2003 through 2007.

Methods

The costs of work related MSDs and CTS in the US were estimated using the cost-of-illness, human capital method (Leigh et al., 2000), using some of the costs from the literature. This method decomposes costs into direct and indirect categories. Estimates of total cost of MSDs and CTS were obtained from the product of average costs of MSDs and CTS and the number of MSDs and CTS. The number of MSDs and CTS were obtained from BLS data.

Results

The number of reported work-related MSDs declined from 435,180 in 2003 to 335,390 in 2007 and the reported number of CTS also declined from 22,110 in 2003 to 11,920 in 2007. The direct costs of MSDs and CTS were respectively $1.5 billion and $0.1 billion for the year 2007. The indirect costs were $1.1 billion and $0.1 billion for MSDs and CTS respectively for the year 2007.

Discussion

This study found that the total costs of work-related MSDs and CTS declined during the period 2003 through 2007 but the average costs per case went up signifying that medical costs and other associated costs increased during this period.

Relevance to industry

The costs of MSDs are important to the industries too as a significant part of these costs are borne by the employers. Industries with higher prevalence of MSDs are affected more in terms of lost productivities due to the employees' days away from work because of MSDs. In cases of MSDs causing permanent disabilities, new hiring and training costs are also a part of the losses experienced by the employers.     

Validity and reliability of a novel device for bilateral upper extremity functional measurements

Background and objective

This study was designed to establish the validity and reliability of a new device that measures bilateral shoulder and elbow range of motion (ROM) and grip force performance in vivo. A further aim was to investigate the control of inter-limb grip force coordination during isometric force-maintenance tasks. Validity of the ROM and grip force measurements was examined using a validated clinical goniometer and standard weights.

Subjects

Twenty-one healthy adults (six female, 15 male; mean ± standard deviation age = 23.05 ± 3.51) were recruited for this study.

Design

All subjects were asked to perform tests to evaluate the validity and reliability of ROM, grip force maximum voluntary contraction (MVC) and coordination control measurements.

Results

The ROM and grip force measurements were linearly correlated with criterion standards. For reliability testing, all of the intraclass correlation coefficient values were >0.99. The inter-limb grip force coordination control task showed that the force modulation timing during dominant-to-non-dominant hand transition was longer than the non-dominant-to-dominant hand transition (p < 0.05).

Conclusions

These results demonstrate that this device is valid and reliable when used to measure shoulder and elbow ROM and grip force of both hands. Isometric force-maintenance tasks also indicated changes in inter-limb grip force control.     

A field intervention examining the impact of an office ergonomics training and a highly adjustable chair on visual symptoms in a public sector organization

Objective

Examine the effect of a multi-component office ergonomics intervention on visual symptom reductions.

Methods

Office workers were assigned to either a group receiving a highly adjustable chair with office ergonomics training (CWT), a training-only group (TO) or a control group (C). A work environment and health questionnaire was administered 2 and 1 month(s) pre-intervention and 3, 6, and 12 months post-intervention. Multi-level statistical models tested hypotheses.

Results

The CWT intervention lowered daily visual symptoms (p < 0.01) post-intervention. The TO group did not significantly differ from the control group. The CWT group differed significantly from the TO group (p = 0.01) post-intervention.

Conclusion

Workers who received a highly adjustable chair and office ergonomics training had reduced visual symptoms and the effect was maintained through twelve months post-intervention. The lack of a training-only group effect supports implementing training in conjunction with the highly adjustable chair to reduce visual symptoms.     

Exploring physical exposures and identifying high-risk work tasks within the floor layer trade

Introduction

Floor layers have high rates of musculoskeletal disorders yet few studies have examined their work exposures. This study used observational methods to describe physical exposures within floor laying tasks.

Methods

We analyzed 45 videos from 32 floor layers using Multimedia-Video Task Analysis software to determine the time in task, forces, postures, and repetitive hand movements for installation of four common flooring materials. We used the WISHA checklists to define exposure thresholds.

Results

Most workers (91%) met the caution threshold for one or more exposures. Workers showed high exposures in multiple body parts with variability in exposures across tasks and for different materials. Prolonged exposures were seen for kneeling, poor neck and low back postures, and intermittent but frequent hand grip forces.

Conclusions

Floor layers experience prolonged awkward postures and high force physical exposures in multiple body parts, which probably contribute to their high rates of musculoskeletal disorders.     

Variation in work tasks in relation to pinch grip strength among middle-aged female dentists

Objectives

We aimed to investigate the relationship of task variation during dental work history with pinch grip strength among dentists.

Methods

We measured pinch grip strength among 295 female Finnish dentists aged 45–63 years. Variation in dental work tasks during work history was empirically defined by cluster analysis. Three clusters of task variation emerged: low (most work time in restoration treatment/endodontics), moderate (about 50% in the former and 50% in prosthodontics/periodontics/surgery), and high (variable tasks including administrative duties). Hand radiographs were examined for the presence of OA in the wrist and each joint of the 1–3rd fingers. Information on hand-loading leisure-time activities, and joint pain was obtained by questionnaire. Glove size was used as a proxy for hand size. BMI (kg/m2) was based on measured weight and self-reported height.

Results

Dentists with low variation of work task history had an increased risk of low pinch grip strength in the right hand (OR 2.3, 95% CI 1.2–4.3), but not in the left (1.13, 0.62–2.08), compared to dentists with high task variation, independent of age, hand size, hand-loading leisure-time activities, BMI and symptomatic hand OA.

Conclusion

The dentists with the most hand-loading tasks were at an increased risk of low pinch grip strength, independent of e.g. symptomatic hand OA. It is advisable among dentists to perform as diverse work tasks as possible to reduce the risk of decreased pinch grip strength.     

Computer program in the treatment for major depression and cognitive impairment in university students

Introduction

A depressed patient presents cognitive impairment that remains in spite of depression’s remission. This study intends to evaluate the impact of cognitive training in the treatment of depression, and also of the impairment that depression causes.

Method

A program for cognitive training (Alcor) was designed for and applied to a group of patients (n = 10) with non-medicated MDD; a group (N = 10) with MDD that was treated with the program and with anti-depressants, and to another group (n = 11) that was given anti-depressors only. The impact of this intervention was assessed by applying the following instruments: Beck Depression Inventory, WAIS, Spielberger State-Trait Anxiety Inventory, Externalized Problems Assessment Scale for Adolescents and Young Adults, and Attention Problems Assessment Scale. The program was applied to University students with MDD twice a week, until they had reached adequate levels of execution.

Results

The patients of all three groups showed MDD event remission. Those who received cognitive training showed a substantial increase of intellectual performance. The cognitive treatment group increased IQ in 12.9 units and the combined group increase in 13.3 units. There was a slight decrease of 1.9 units within the anti-depressant treatment group. The changes in attention and in externalized problems showed the same trends.     

Augment low-field intra-operative MRI with preoperative MRI using a hybrid non-rigid registration method

Background

Preoperatively acquired diffusion tensor image (DTI) and blood oxygen level dependent (BOLD) have been proved to be effective in providing more anatomical and functional information; however, the brain deformation induced by brain shift and tumor resection severely impairs the correspondence between the image space and the patient space in image-guided neurosurgery.

Method

To address the brain deformation, we developed a hybrid non-rigid registration method to register high-field preoperative MRI with low-field intra-operative MRI in order to recover the deformation induced by brain shift and tumor resection. The registered DTI and BOLD are fused with low-field intra-operative MRI for image-guided neurosurgery.

Results

The proposed hybrid registration method was evaluated by comparing the landmarks predicted by the hybrid registration method with the landmarks identified in the low-field intra-operative MRI for 10 patients. The prediction error of the hybrid method is 1.92 ± 0.54 mm, and the compensation accuracy is 74.3 ± 5.0%. Compared to the landmarks far from the resection region, those near the resection region demonstrated a higher compensation accuracy (P-value = .003) although these landmarks had larger initial displacements.

Conclusions

The proposed hybrid registration method is able to bring preoperatively acquired BOLD and DTI into the operating room and compensate for the deformation to augment low-field intra-operative MRI with rich anatomical and functional information.     

Validation of reported events from a vertical chute marine evacuation study

Background

The use of vertical chute marine evacuation systems (MES) is now well established on board marine passenger vessels; this system has yet to be deployed in an emergency situation, however, it has been associated with a fatality and several major injuries during training. Brunel University's Ethics Committee endorsed an initial retrospective cross sectional study (Harwood and Farrow, 2008) and the present quantitative observational study. Harwood and Farrow (2008) found that the physical, physiological and psychological characteristics of potential evacuees increased the likelihood of injury and adversely affected the reliability of the system.

Purpose

The validation of factors associated with the adverse outcomes recorded by Harwood and Farrow (2008) during vertical chute MES training, and to assess the hypothesis that evacuee's clothing material will affect the efficiency of the system.

Design

Observational data in a marine training establishment providing a triangulation measurement process of evidence from the retrospective study (Harwood and Farrow, 2008). Subjects were three hundred and seventy five representative participants on training courses for evacuation from a ship into inflated life rafts. The main outcome measures were stopping during descent and exiting the chute in an undesirable position.

Results

6.1% stopped momentarily during descent; 20.3% exited the chute in an undesirable position; on entering the raft 7.7% flipped over and 9.1% had their legs tucked up under their bodies. Independent variables including evacuees' clothing material were statistically significantly associated with adverse outcomes. Participants stopping during descent had an RR of 3.03 (95% CI 1.38, 6.64) for exiting the chute in an undesirable position.

Conclusions

This quantitative observational study broadly supported the results obtained from the retrospective cross sectional study (Harwood and Farrow, 2008). Stopping during descent and evacuee clothing increased the likelihood of undesirable outcomes and impacted on the efficiency of the system.     

Who benefits from simulator training: Personality and heart rate variability in relation to situation awareness during navigation training

Objective

This study tested the relationship between individual differences and Situation Awareness (SA) during training in a navigation simulator.

Background

Simulators have become an important tool in the training and education of maritime personnel with a view to improving decisions and performance. There are a few, inconclusive empirical studies that have focused on mapping personality characteristics and their link to the ability to generate and maintain SA during simulator training.

Method

Thirty-six first-year students from the Royal Norwegian Navy Officer Candidate School participated in the study. SA was measured using both subjective and observer ratings.

Results

The results indicated that low scores on Neuroticism and high scores on Extraversion and Conscientiousness (resilient personality type) predicted both subjective and observer-rated SA. Furthermore, participants with high SA were able to modulate their Heart Rate Variability (HRV), with suppression of HRV during navigation training as well showing recovery of HRV.

Application

The potential applications of this research include the assessment of personality differences as a tool in selecting navigators, and the use of HRV as an objective index of adaptability to environmental demands.     

FMS™ scores and low-back loading during lifting – Whole-body movement screening as an ergonomic tool?

Background

Previous research suggests that a general whole-body movement screen could be used to identify personal movement attributes that promote potentially injurious low-back loading patterns at work. The purpose of this study was to examine the relationship between Functional Movement Screen™ (FMS) composite scores and the low-back loading response to lifting.

Methods

Fifteen men who scored greater than 14 on the FMS (high-scorers) and 15 height- and weight-matched low-scorers (FMS < 14) performed sagittally symmetric and asymmetric laboratory-based lifting tasks. A three-dimensional dynamic biomechanical model was used to calculate peak low-back loading levels, and the angle of the lumbar spine was captured at the instant when the peak compressive force was applied.

Results

Regardless of the lifting task performed, there were no differences in peak low-back compression (p ≥ 0.4157), anterior/posterior reaction shear (p ≥ 0.5645), or medial/lateral reaction shear (p ≥ 0.2581) forces between the high- and low-scorers. At the instant when peak compressive forces were applied, differences in the lumbar spine angle between high- and low-scores were not statistically significant about the lateral bend (p ≥ 0.4215), axial twist (p ≥ 0.2734), or flexion/extension (p ≥ 0.1354) axes, but there was a tendency for the lumbar spine to be more deviated in the low-scorers.

Conclusions

Using the previously established injury prediction threshold value of 14, the composite FMS score was not related to the peak low-back loading magnitudes in lifting. Though not statistically significant, the tendency for the lumbar spines of low-scorers to be more deviated when the peak low-back compression force was imposed could be biomechanically meaningful because spinal load tolerance varies with posture. Future attempts to modify or reinterpret FMS scoring are warranted given that several previous studies have revealed links between composite FMS scores and musculoskeletal complaints.     

A web-based learning tool improves student performance in statistics: A randomized masked trial

Background

e-status is a web-based tool able to generate different statistical exercises and to provide immediate feedback to students’ answers. Although the use of Information and Communication Technologies (ICTs) is becoming widespread in undergraduate education, there are few experimental studies evaluating its effects on learning.

Method

All of the students (121) from an introductory course for statistics in dentistry were randomly assigned to use the tool with one of two 6-problem sets, known as types A and B. The primary endpoint was the grade difference obtained in the final exam, composed of two blocks of questions related to types A and B. The exam evaluator was masked to the intervention group.

Results

We found that the effect of e-status on the student grade was an improvement of 0.48 points (95% CI: 0.10–0.86) on a ten-point scale. Among the 94 students who actually employed e-status, the effect size was 0.63 (95% CI: 0.17–1.10).

Conclusions

It is feasible to formally assess the learning effect of an innovative tool. Providing e-status exercises to students has a direct effect on learning numerical operations related to statistics. Further effects on higher cognitive levels still have to be explored.     

Influence of wearing an unstable shoe on thigh and leg muscle activity and venous response in upright standing

Purpose

To quantify the effect of unstable shoe wearing on muscle activity and haemodynamic response during standing.

Methods

Thirty volunteers were divided into 2 groups: the experimental group wore an unstable shoe for 8 weeks, while the control group used a conventional shoe for the same period. Muscle activity of the medial gastrocnemius, tibialis anterior, rectus femoris and biceps femoris and venous circulation were assessed in quiet standing with the unstable shoe and barefoot.

Results

In the first measurement there was an increase in medial gastrocnemius activity in all volunteers while wearing the unstable shoe. On the other hand, after wearing the unstable shoe for eight weeks these differences were not verified. Venous return increased in subjects wearing the unstable shoe before and after training.

Conclusions

The unstable shoe produced changes in electromyographic characteristics which were advantageous for venous circulation even after training accommodation by the neuromuscular system.     

Optimization of novel spectral estimator for fractionated electrogram analysis is helpful to discern atrial fibrillation type

Introduction

Paroxysmal versus persistent atrial fibrillation (AF) can be distinguished based on differences in the spectral parameters of fractionated atrial electrograms. Maximization of these differences would improve characterization of the arrhythmogenic substrate. A novel spectral estimator (NSE) has been shown previously to provide greater distinction in AF spectral parameters as compared with the Fourier transform estimator. Herein, it is described how the differences in NSE spectral parameters can be further improved.

Method

In 10 persistent and 9 paroxysmal AF patients undergoing electrophysiologic study, fractionated electrograms were acquired from the distal bipolar ablation electrode. A total of 204 electrograms were recorded from the pulmonary vein (PV) antra and from the anterior and posterior left atrial free wall. The following spectral parameters were measured: the dominant frequency (DF), which reflects local activation rate, the DF amplitude (DA), and the mean spectral profile (MP), which represents background electrical activity. To optimize differences in parameters between paroxysmal versus persistent AF patients, the NSE was varied by selectively removing subharmonics, using a threshold. The threshold was altered in steps to determine the optimal subharmonics removal.

Results

At the optimal threshold level, mean differences in persistent versus paroxysmal AF spectral parameters were: ΔDA = +0.371 mV, ΔDF = +0.737 Hz, and ΔMP = −0.096 mV. When subharmonics were not removed, the differences were substantially less: ΔDA = +0.301 mV, ΔDF = +0.699 Hz, and ΔMP = −0.063 mV.

Conclusions

NSE optimization produces greater spectral parameter difference between persistent versus paroxysmal AF data. Quantifying spectral parameter differences can be assistive in characterizing the arrhythmogenic substrate.     

Kinematic and electromyographic differences between mouse and touchpad use on laptop computers

Background

Numerous studies have compared the postures and muscular activities induced by the various input devices available. To the authors' knowledge, no studies have yet compared upper body posture and movement, sEMG activity and muscle co-contractions induced by use of a mouse or of a touchpad.

Objective

The aim of this study was to compare posture, joint excursion and sEMG activity when using a laptop equipped with a mouse or a touchpad.

Methods

Trunk and upper arm posture, ranges of motion and muscle activities were measured in ten subjects during two standardized tasks.

Results

Mouse use induced larger shoulder abduction than touchpad use. On the other hand, when a touchpad was used, the upper arm joints were bound and fixed to a greater extent than during mouse use. Touchpad users are forced to maintain a more static posture. The upper arm electromyography results clearly indicate that touchpad use requires more stabilization than mouse use.

Conclusion

Motor tasks executed by means of the mouse allow a greater range of motions and reduce the biomechanical stress thanks to the greater postural mobility, even though the posture is less neutral. The results of our study tend to suggest that an external mouse should be preferred to the touchpad by frequent users of laptops.

Relevance to industry

This study is a suggestion for IT companies to give customers information of possible advantages using an external mouse. Furthermore our data highlight the importance of providing a mouse to all laptop users in order to reduce biomechanical risks.     

Evaluation of a haptics-based virtual reality temporal bone simulator for anatomy and surgery training

Introduction

Virtual reality simulation training may improve knowledge of anatomy and surgical skills. We evaluated a 3-dimensional, haptic, virtual reality temporal bone simulator for dissection training.

Methods

The subjects were 7 otolaryngology residents (3 training sessions each) and 7 medical students (1 training session each). The virtual reality temporal bone simulation station included a computer with software that was linked to a force-feedback hand stylus, and the system recorded performance and collisions with vital anatomic structures. Subjects performed virtual reality dissections and completed questionnaires after the training sessions.

Results

Residents and students had favorable responses to most questions of the technology acceptance model (TAM) questionnaire. The average TAM scores were above neutral for residents and medical students in all domains, and the average TAM score for residents was significantly higher for the usefulness domain and lower for the playful domain than students. The average satisfaction questionnaire for residents showed that residents had greater overall satisfaction with cadaver temporal bone dissection training than training with the virtual reality simulator or plastic temporal bone. For medical students, the average comprehension score was significantly increased from before to after training for all anatomic structures. Medical students had significantly more collisions with the dura than residents. The residents had similar mean performance scores after the first and third training sessions for all dissection procedures.

Discussion

The virtual reality temporal bone simulator provided satisfactory training for otolaryngology residents and medical students.     

Successful implementation of user-centered game based learning in higher education: An example from civil engineering

Goal

The use of an online game for learning in higher education aims to make complex theoretical knowledge more approachable. Permanent repetition will lead to a more in-depth learning.

Objective

To gain insight into whether and to what extent, online games have the potential to contribute to student learning in higher education.

Experimental setting

The online game was used for the first time during a lecture on Structural Concrete at Master’s level, involving 121 seventh semester students.

Methods

Pre-test/post-test experimental control group design with questionnaires and an independent online evaluation.

Results

The minimum learning result of playing the game was equal to that achieved with traditional methods. A factor called “joy” was introduced, according to [Nielsen, J. (2002): User empowerment and the fun factor. In Jakob Nielsen’s Alertbox, July 7, 2002. Available from http://www.useit.com/alertbox/20020707.html.], which was amazingly high.

Conclusion

The experimental findings support the efficacy of game playing. Students enjoyed this kind of e-learning.     

Nomophobia: Dependency on virtual environments or social phobia?

Background

The increasing use of new technologies and virtual communication involving personal computers (PCs), tablets and mobile phones are causing changes in individuals’ daily habits and behavior. We report the case of an individual with social phobia who developed a dependency on communication through virtual environments (i.e., nomophobia), and used a PC as a form of relating to the outside world to reduce stress and to avoid direct social relations. Nomophobia refers to the discomfort or anxiety caused by the non-availability of a mobile phone, PC or any another virtual communication device. Social phobia is described as an anxiety disorder of chronic evolution.

Objective

To study nomophobia as a manifest behavior that might serve as an indication of a possible anxiety disorder.

Methodology

The treatment consisted of the use of medication, cognitive-behavioral therapy (CBT) and the application of evaluation tools (interviews, scales, inventories and questionnaires).

Results

The individual responded satisfactorily to medication and CBT treatment, which reduced his time using the PC and increased his exposure to real-life situations.

Conclusion

Nomophobic behavior produces changes in daily habits and can reveal other aspects to be investigated, such as the presence of comorbid mental disorders.     

Infection risk in patients with rheumatoid arthritis treated with etanercept or adalimumab

Objectives

To compare the risk of infection for rheumatoid arthritis (RA) patients who took etanercept or adalimumab medication in a nationwide population.

Methods

RA patients who took etanercept or adalimumab were identified in the Taiwan's National Health Insurance Research Database. The composite outcome of serious infections, including hospitalization for infection, reception of an antimicrobial injection, and tuberculosis were followed for 365 days. A Kaplan–Meier survival curve with a log-rank test and Cox proportional hazards regression were used to compare risks of infection between the two cohorts of tumor necrosis factor (TNF)-α antagonists users. Hazard ratios (HRs) were obtained and adjusted with propensity scores and clinical factors. Sensitivity analyses and subgroup analyses were also performed.

Results

In total, 1660 incident etanercept users and 484 incident adalimumab users were eligible for the analysis. The unadjusted HR for infection of the etanercept users was significantly higher than that of the adalimumab users (HR: 1.93; 95% confidence interval (CI): 1.09–3.42; p = 0.024). The HRs were 2.04 (95% CI: 1.14–3.65; p = 0.016) and 2.02 (95% CI: 1.13–3.61; p = 0.018) after adjusting for propensity scores and for propensity scores in addition to clinical factors, respectively. The subgroup analyses revealed that HRs for composite infection was significantly higher in patient subgroups of older age, female, as well as patients who did not have DM, COPD, and hospitalization history at the baseline.

Conclusion

In this head-to-head cohort study involving a nationwide population of patients with RA, etanercept users demonstrated a higher risk of infection than adalimumab users. Results of this study suggest the possible existence of an intra-class difference in infection risk among TNF-α antagonists.