Tests of platelet function

PURPOSE OF REVIEW: Platelets play a vital role in the normal hemostasis, and derangements of their function can lead to hemorrhage or thrombosis. While we have made progress in elucidating the molecular mechanisms leading to platelet adhesion, aggregation, shape change, and secretion, clinically useful tests of platelet function have lagged behind. The following is a review of some of the currently available tests of platelet function, their advantages and drawbacks, as well as the clinical scenarios in which they are likely to be useful. RECENT FINDINGS: Attention is now being paid to standardization and optimization of older tests such as platelet aggregometry, in addition to better defining the role of newer tests such as the platelet function analyzer and thromboelastography in diagnosing and managing disorders of primary hemostasis and platelet function. SUMMARY: Platelet function is complex and may be disrupted at any of a number of steps, including adhesion, aggregation, shape change and secretion. We are better defining the role of the currently available tests, while identifying gaps in our ability to diagnose disorders of platelet function.     

Representation of capsaicin-evoked urge-to-cough in the human brain using functional magnetic resonance imaging

RATIONALE: Coughing in humans is typically preceded by a desire (or urge) to cough. The neural circuitry involved in sensing airway irritation and generating the urge-to-cough in humans is essentially unknown. OBJECTIVES: The aim of the present study was to use functional brain imaging to describe the supramedullary regions that are activated in humans during capsaicin inhalation. METHODS: Experiments were performed on 10 healthy subjects (5 males, 5 females). Capsaicin doses were individually tailored to evoke a transient and reversible urge-to-cough. Blood oxygen level-dependent (BOLD) functional magnetic resonance measures were collected during repeated 24-second challenges with capsaicin or saline inhalation and subjects were asked to rate the urge-to-cough intensity of each challenge. MEASUREMENTS AND MAIN RESULTS: Capsaicin inhalation reliably evoked an urge-to-cough, which was associated with activations in a variety of brain regions, including the insula cortex, anterior midcingulate cortex, primary sensory cortex, orbitofrontal cortex, supplementary motor area, and cerebellum. CONCLUSIONS: These data provide the first insights into the cortical neuronal network involved in sensing airway irritation and modulating coughing in humans.     

Effect of lung volume reduction surgery on resting pulmonary hemodynamics in severe emphysema

RATIONALE: To determine the effect of medical treatment versus lung volume reduction surgery (LVRS) on pulmonary hemodynamics. METHODS: Three clinical centers of the National Emphysema Treatment Trial (NETT) screened patients for additional inclusion into a cardiovascular (CV) substudy. Demographics were determined, and lung function testing, six-minute-walk distance, and maximum cardiopulmonary exercise testing were done at baseline and 6 months after medical therapy or LVRS. CV substudy patients underwent right heart catheterization at rest prerandomization (baseline) and 6 months after treatment. MEASUREMENTS AND MAIN RESULTS: A total of 110 of the 163 patients evaluated for the CV substudy were randomized in NETT (53 were ineligible), 54 to medical treatment and 56 to LVRS. Fifty-five of these patients had both baseline and repeat right heart catheterization 6 months postrandomization. Baseline demographics and lung function data revealed CV substudy patients to be similar to the remaining 1,163 randomized NETT patients in terms of age, sex, FEV(1), residual volume, diffusion capacity of carbon monoxide, Pa(O(2)), Pa(CO(2)), and six-minute-walk distance. CV substudy patients had moderate pulmonary hypertension at rest (Ppa, 24.8 +/- 4.9 mm Hg); baseline hemodynamic measurements were similar across groups. Changes from baseline pressures to 6 months post-treatment were similar across treatment groups, except for a smaller change in pulmonary capillary wedge pressure at end-expiration post-LVRS compared with medical treatment (-1.8 vs. 3.5 mm Hg, p = 0.04). CONCLUSIONS: In comparison to medical therapy, LVRS was not associated with an increase in pulmonary artery pressures.     

Testing practices and knowledge of HIV among prenatal care providers in a low seroprevalence state

As the prevalence of heterosexually transmitted HIV increases among women of childbearing age in the United States, so too does the potential for vertical transmission from mother to child. Early maternal diagnosis and appropriate management are critical to minimizing the risk of perinatal infection. We designed a study to evaluate current prenatal care provider testing practices and knowledge of HIV as it relates to pregnancy in a low seroprevalence state. A written questionnaire was mailed to 642 prenatal care providers in Kentucky. Responses were compared to a similar survey conducted in 1998 and to current federal guidelines for HIV management. Nearly all respondents reported to offer HIV testing to all prenatal patients, demonstrating a marked improvement since 1998 (p < 0.001). However, clinicians did not report adequate follow-up when testing is refused and appear to have limited knowledge of the disease as it relates to pregnancy. Only 9.3% of respondents demonstrated proficiency on two knowledge assessment questions. Those with previous experience treating prenatal patients with HIV were more likely to respond correctly (odds ratio [OR] 3.03; 95% confidence interval [CI] 1.08-8.50). Providers with little experience treating patients with HIV may not possess the basic knowledge required to manage the disease during pregnancy. Additional educational interventions are needed in low seroprevalence areas to ensure the appropriate treatment of all HIV-positive pregnant patients and to minimize the risk of preventable perinatal transmission.     

Patterns of self-disclosure in psychotherapy and marriage

This study compared patterns of self-disclosure in psychotherapy and marriage. Participants (48 married, current psychotherapy patients, mean age = 42) completed a 101-item Disclosure to Therapist Inventory and a companion measure, a 101-item Disclosure to Spouse Inventory. Results indicated a pattern of greater disclosure to one's therapist in regard to issues involving despair (e.g., feelings of depression), and to one's spouse in regard to procreation and body concerns (e.g., birth control) and values (e.g., feelings about religion, race, or politics). Issues involving sex were infrequently discussed in either context. Discrepancy scores (differences between extent of disclosure and perceived importance) were greater in the spouse condition. Outcome predictors varied by situation, with overall disclosure predicting therapeutic outcome and both overall disclosure and discrepancy scores predicting marital satisfaction. Findings suggest that although there is substantial overlap in issues discussed in these two contexts, certain intimate disclosures are perceived as situation-specific. (PsycINFO Database Record (c) 2010 APA, all rights reserved).     

Enhanced stimulus strength improves visual cognition in aging and Alzheimer's disease

Deficits in visual cognition in Alzheimer's disease (AD) arise from neuropathological changes in higher-order association areas of the cortex and from defective input from lower-level visual processing areas. We investigated whether enhanced signal strength may lead to improvement of visual cognition in AD. We tested 35 individuals with probable AD, 35 age-matched elderly control (EC) and 58 young control (YC) adults on letter identification, word reading, picture naming, discrimination of unfamiliar faces, and pattern completion. The contrast sensitivity step-difference across an independent sample of AD and EC groups was used in calculating an image filter, from which we produced stimulus-strength conditions of low-degraded, medium-normal, and high-enhanced. Using this filter we created a hypothetical proximal-strength equivalence between AD at medium strength and EC at low strength, and between AD at high strength and EC at medium strength. For letter identification, word reading, picture naming, and face discrimination, medium strength elicited AD accuracy levels and reaction times that were similar to those of EC at low strength. On picture naming, increased strength reduced perceptual-type errors for EC and AD and random errors for AD. For word reading, high strength elicited AD accuracy levels and reaction times that were equivalent to those of EC at medium strength. We saw no effect of signal-strength manipulation on performance of pattern completion, possibly owing to the complex cognitive demands of that task or to the inadequacy of the filter for its images. The results indicate that putative AD-EC differences in cognition directly reflect contrast sensitivity differences between the groups. Enhancement of stimulus strength can ameliorate vision-based deficits and lead to improvement in some aspects of cognitive performance. These results suggest new non-pharmacological avenues to explore in the attempt to improve cognition in elderly adults and especially in individuals with AD.     

Trunk performance after stroke: an eye catching predictor of functional outcome

Background and aim

Trunk performance is an important predictor of functional outcome after stroke. However, the percentage of explained variance varies considerably between studies. This may be explained by the stroke population examined, the different scales used to assess trunk performance and the time points used to measure outcome. The aim of this multicentre study was to examine the predictive validity of the Trunk Impairment Scale (TIS) and its subscales when predicting the Barthel Index score at 6 months after stroke.

Methods

A total of 102 subjects were recruited in three European rehabilitation centres. Participants were assessed on admission (median time since stroke onset 20 days) and 6 months after stroke. Correlation analysis and forward stepwise multiple regression analysis were used to model outcome.

Results

The best predictors of the Barthel Index scores at 6 months after stroke were total TIS score (partial R² = 0.52, p<.0001) and static sitting balance subscale score (partial R² = 0.50, p<.0001) on admission. The TIS score on admission and its static sitting balance subscale were stronger predictors of the Barthel Index score at 6 months than the Barthel Index score itself on admission.

Conclusions

This study emphasises the importance of trunk performance, especially static sitting balance, when predicting functional outcome after stroke. The TIS is recommended as a prediction instrument in the rehabilitation setting when considering the prognosis of stroke patients. Future studies should address the evolution of trunk performance over time and the evaluation of treatment interventions to improve trunk performance.Although the age specific incidence of major stroke has fallen over the past few years,¹ it is still the main cause of long term disability in adults, with a growing number of survivors being dependent for activities of daily living (ADL).^2,3 Frequently identified variables predicting ADL after stroke are age and initial severity of motor and functional deficits.⁴ Trunk performance has also been identified as an important independent predictor of ADL after stroke.^5,6,7,8,9 However, based on multiple regression analyses, the reported variance of functional outcome after stroke explained by trunk performance ranges from 9% to 71%.^5,6,7,8,9 Differences in reported variance could be explained by the stroke population included, the various scales used to measure trunk performance and the time points used to measure outcome.Previous studies evaluating the predictive validity of trunk performance after stroke were performed in a single rehabilitation setting, warranting caution when generalising results.^5,6,7,8,9,10 Clinical tools used to assess trunk performance are the Trunk Control Test,^5,6,10 trunk control items of the Postural Assessment Scale for Stroke patients^7,8 and trunk assessment of Fujiwara et al.⁹ A limitation of the first two tests is that they both have a ceiling effect, which makes their use less suitable in long term outcome studies.^5,11,12,13 Furthermore, the trunk control items of the Trunk Control Test and Postural Assessment Scale for Stroke patients are largely comparable with the items of the trunk measure of Fujiwara et al.⁹ All previously mentioned clinical tools include items in the supine position which involve rolling as well as only basic balance movements in sitting. Finally, with the exception of the trunk control items of the Postural Assessment Scale for Stroke patients,⁸ no study has evaluated the prognostic value of trunk performance when predicting functional outcome at 6 months after stroke.The Trunk Impairment Scale (TIS) for patients after stroke was designed to measure ADL related selective trunk movements rather than participation of the trunk in gross transfer movements.¹⁴ The TIS assesses static and dynamic sitting balance and trunk coordination. Reliability, validity, measurement error, internal consistency and discriminant ability of the TIS have been reported elsewhere.^14,15 The TIS has no ceiling effect in subacute and chronic stroke patients and already appeared to be strongly related to measures of gait, balance and functional ability in a cross sectional study.¹² To the best of our knowledge, the predictive value of the TIS and its subscales has not been evaluated. Including age and other measures of motor and functional performance could provide a useful combination of variables predicting outcome after stroke. The Barthel Index score is a widely accepted measure in stroke rehabilitation research and assesses functional milestones in stroke recovery. Predicting Barthel Index scores at 6 months after stroke based on measurements taken on admission to a rehabilitation centre would further establish the importance of trunk performance when predicting long term outcome after stroke. Experts in the field of neurological rehabilitation have addressed the trunk as the central key point of the body.¹⁶ Proximal stability of the trunk is a prerequisite for distal head and limb movement and therefore expected to be related to functional ADL.In summary, there is still a lack of clarity regarding the importance of trunk performance in functional outcome after stroke. Scales which have been used in previous studies have important statistical limitations and are likely to be a comprehensive measure of motor performance of the trunk. Therefore, the aim of this multicentre study was to examine the predictive validity of the TIS and its subcomponents, together with other known predictors, in predicting functional outcome measured as a Barthel Index score at 6 months after stroke.