John P. Collins

Estimation of diagnostic test accuracy without full verification: a review of latent class methods

The performance of a diagnostic test is best evaluated against a reference test that is without error. For many diseases, this is not possible, and an imperfect reference test must be used. However, diagnostic accuracy estimates may be biased if inaccurately verified status is used as the truth. Statistical models have been developed to handle this situation by treating disease as a latent variable. In this paper, we conduct a systematized review of statistical methods using latent class models for estimating test accuracy and disease prevalence in the absence of complete verification.

Effect of Aerobic Exercise Training on Mood in People With Traumatic Brain Injury: A Pilot Study

Background: Exercise training is associated with elevations in mood in patients with various chronic illnesses and disabilities. However, little is known regarding the effect of exercise training on short and long-term mood changes in those with traumatic brain injury (TBI). Objective: The purpose of this study was to examine the time course of mood alterations in response to a vigorous, 12-week aerobic exercise training regimen in ambulatory individuals with chronic TBI (>6 months postinjury). Methods: Short and long-term mood changes were measured using the Profile of Mood States-Short Form, before and after specific aerobic exercise bouts performed during the 12-week training regimen. Results: Ten subjects with nonpenetrating TBI (6.6 ± 6.8 years after injury) completed the training regimen. A significant improvement in overall mood was observed following 12 weeks of aerobic exercise training (P = .04), with moderate to large effect sizes observed for short-term mood improvements following individual bouts of exercise. Conclusions: Specific improvements in long-term mood state and short-term mood responses following individual exercise sessions were observed in these individuals with TBI. The largest improvement in overall mood was observed at 12 weeks of exercise training, with improvements emerging as early as 4 weeks into the training regimen.

Estimating diagnostic accuracy without a gold standard: A continued controversy

ABSTRACT There is a wide body of literature in biostatistics and epidemiology literature about estimating diagnostic accuracy, such as sensitivity and specificity of a binary test, without a gold standard. This methodology is very attractive since obtaining gold standard information is impossible, difficult, or very expensive in some situations. Although there are many proponents of these approaches, there have also been some serious criticisms. We review important methodological developments as well as discuss problems with the approaches. We propose alternative designs that may be less controversial and present ideas for future research. Lastly, we provide recommendations about how these methods should be used in practice.

Effects of overground locomotor training on the ventilatory response to volitional treadmill walking in individuals with incomplete spinal cord injury: a pilot study

Introduction:Although there has been substantial emphasis on the neuromuscular and cardiovascular adaptations following rehabilitation, pulmonary adaptations in individuals with incomplete SCI (iSCI) in response to locomotor training have been less frequently studied. In healthy individuals, effective transition from rest to work is accomplished by a hyperpneic response, which exhibits an exponential curve with three phases. However, the degree to which our current understanding of exercise hyperpnea can be applied to individuals with iSCI is unknown. The purpose of this case series was to characterize exercise hyperpnea during a rest to constant work rate (CWR) transition before and after 12–15 weeks of overground locomotor training (OLT).Case Presentation:Six subjects with cervical motor incomplete spinal cord injury participated in 12–15 weeks of OLT. Subjects were trained in 90-min sessions twice a week. All training activities were weight-bearing and under volitional control without the assistance of body-weight support harnesses, robotic devices or electrical stimulation. Six minutes of CWR treadmill walking was performed at self-selected pace with cardiorespiratory analysis throughout the tests before and after OLT. Averaged group data for tidal volume, breathing frequency or VE showed no difference before and after training. VE variability was decreased by 46.7% after OLT.Discussion:CWR VE from rest to work was linear throughout the transition. Following OLT, there was a substantial reduction in VE variability. Future research should investigate the lack of a phasic ventilatory response to exercise, as well as potential mechanisms of ventilatory variability and its implications for functional performance.