Publications

BACKGROUND

Low-risk chest pain is a common cause of hospital admission; however, to our knowledge, there are no guidelines regarding the appropriate use of stress testing in such cases.

METHODS

We performed a retrospective cohort study of patients 21 years and older who were admitted to our tertiary care center with chest pain in 2007 and 2008. Using electronic records and chart review, we sought (1) to identify differences in the use of stress testing based on patient demographics and comorbidities, pretest probability of coronary artery disease, and house staff coverage and (2) to describe the results of stress testing and patient outcomes, including revascularization procedures and 30-day readmissions for myocardial infarction.

RESULTS

Of 2107 patients, 1474 (69.9%) underwent stress tests, and the results were abnormal in 184 patients (12.5%). Within 30 days, 22 patients (11.6%) with abnormal test results underwent cardiac catheterization, 9 (4.7%) underwent revascularization, and 2 (1.1%) were readmitted for myocardial infarction. In a multivariable model, stress test ordering was positively associated with age younger than 70 years (RR [relative risk], 1.12; 95% CI, 1.02-1.23), private insurance (vs Medicare/Medicaid: RR, 1.19; 95% CI, 1.11-1.27), and no house staff coverage (RR, 1.39; 95% CI, 1.28-1.50). Of patients with low (<10%) pretest probability, 68.0% underwent stress testing, but only 4.5% of these had abnormal test results.

CONCLUSIONS

Most patients who are admitted with low-risk chest pain undergo stress testing, regardless of pretest probability, but abnormal test results are uncommon and rarely acted on. Ordering stress tests based on pretest probability could improve efficiency without endangering patients.

We present a novel and simple method for amplifying RNA targets (named by its acronym, SMART), and for detection, using engineered amplification probes that overcome existing limitations of current RNA-based technologies. This system amplifies and detects optimal engineered ssDNA probes that hybridize to target RNA. The amplifiable probe-target RNA complex is captured on magnetic beads using a sequence-specific capture probe and is separated from unbound probe using a novel microfluidic technique. Hybridization sequences are not constrained as they are in conventional target-amplification reactions such as nucleic acid sequence amplification (NASBA). Our engineered ssDNA probe was amplified both off-chip and in a microchip reservoir at the end of the separation microchannel using isothermal NASBA. Optimal solution conditions for ssDNA amplification were investigated. Although KCl and MgCl(2) are typically found in NASBA reactions, replacing 70 mmol/L of the 82 mmol/L total chloride ions with acetate resulted in optimal reaction conditions, particularly for low but clinically relevant probe concentrations (≤100 fmol/L). With the optimal probe design and solution conditions, we also successfully removed the initial heating step of NASBA, thus achieving a true isothermal reaction. The SMART assay using a synthetic model influenza DNA target sequence served as a fundamental demonstration of the efficacy of the capture and microfluidic separation system, thus bridging our system to a clinically relevant detection problem.

BACKGROUND

Although chronic obstructive pulmonary disease (COPD) is a major cause of disability worldwide, its determinants remain poorly defined.

OBJECTIVE

We hypothesized that both pulmonary and extra-pulmonary factors would predict prospective disablement across a hierarchy of activities in persons with COPD.

METHODS

Six hundred and nine participants were studied at baseline (T0) and 2.5 years later (T1). The Valued Life Activities (VLA) scale quantified disability (10-point scale: 0 = no difficulty and 10 = unable to perform), defining disability as any activity newly rated 'unable to perform' at T1. Predictors included pulmonary (lung function, 6-minute walk distance and COPD severity score) and extra-pulmonary (quadriceps strength and lower extremity function) factors. Prospective disability risk was tested by separate logistic regression models for each predictor (baseline value and its change, T0-T1; odds ratios were scaled at 1 standard deviation per factor. Incident disability across a hierarchy of obligatory, committed and discretionary VLA subscales was compared.

RESULTS

Subjects manifested a 40% or greater increased odds of developing disability for each predictor (baseline and change over time). Disability in discretionary activities developed at a rate 2.2-times higher than observed in committed activities, which was in turn 2.5-times higher than the rate observed in obligatory activities (p < 0.05 for each level).

CONCLUSIONS

Disability is common in COPD. Both pulmonary and extra-pulmonary factors are important in predicting its development.