Exchangeable Working Correlation Matrix Research Articles

Hospital‐reported Data on the Pneumonia Quality Measure “Time to First Antibiotic Dose” Are Not Associated With Inpatient Mortality: Results of a Nationwide Cross‐sectional Analysis

Significant controversy exists regarding the Centers for Medicare & Medicaid Services (CMS) "time to first antibiotics dose" (TFAD) quality measure. The objective of this study was to determine whether hospital performance on the TFAD measure for patients admitted from the emergency department (ED) for pneumonia is associated with decreased mortality. This was a cross-sectional analysis of 95,704 adult ED admissions with a principal diagnosis of pneumonia from 530 hospitals in the 2007 Nationwide Inpatient Sample. The sample was merged with 2007 CMS Hospital Compare data, and hospitals were categorized into TFAD performance quartiles. Univariate association of TFAD performance with inpatient mortality was evaluated by chi-square test. A population-averaged logistic regression model was created with an exchangeable working correlation matrix of inpatient mortality adjusted for age, sex, comorbid conditions, weekend admission, payer status, income level, hospital size, hospital location, teaching status, and TFAD performance. Patients had a mean age of 69.3 years. In the adjusted analysis, increasing age was associated with increased mortality with odds ratios (ORs) of >2.3. Unadjusted inpatient mortality was 4.1% (95% confidence interval [CI] = 3.9% to 4.2%). Median time to death was 5 days (25th-75th interquartile range = 2-11). Mean TFAD quality performance was 77.7% across all hospitals (95% CI = 77.6% to 77.8%). The risk-adjusted OR of mortality was 0.89 (95% CI = 0.77 to 1.02) in the highest performing TFAD quartile, compared to the lowest performing TFAD quartile. The second highest performing quartile OR was 0.94 (95% CI = 0.82 to 1.08), and third highest performing quartile was 0.91 (95% CI = 0.79 to 1.05). In this nationwide heterogeneous 2007 sample, there was no association between the publicly reported TFAD quality measure performance and pneumonia inpatient mortality.

Cost Analysis and Cost Determinants in a European Inflammatory Bowel Disease Inception Cohort With 10 Years of Follow-up Evaluation

Economic analysis in chronic diseases is a prerequisite for planning a proper distribution of health care resources. We aimed to determine the cost of inflammatory bowel disease, a lifetime illness with considerable morbidity. We studied 1321 patients from an inception cohort in 8 European countries and Israel over 10 years. Data on consumption of resources were obtained retrospectively. The cost of health care was calculated from the use of resources and their median prices. Data were analyzed using regression models based on the generalized estimating equations approach. The mean annual total expenditure on health care was 1871 Euro/patient-year for inflammatory bowel disease, 1524 Euro/patient-year for ulcerative colitis, and 2548 Euro/patient-year for Crohn's disease (P < .001). The most expensive resources were medical and surgical hospitalizations, together accounting for 63% of the cost in Crohn's disease and 45% in ulcerative colitis. Total and hospitalization costs were much higher in the first year after diagnosis than in subsequent years. Differences in medical and surgical hospitalizations were the primary cause of substantial intercountry variations of cost; the mean cost of health care was 3705 Euro/patient-year in Denmark and 888 Euro/patient-year in Norway. The outlay for mesalamine, a costly medication with extensive use, was greater than for all other drugs combined. Patient age at diagnosis and sex did not affect costs. In this multinational, population-based, time-dependent characterization of the health care cost of inflammatory bowel disease, increased expenditure was driven largely by country, diagnosis, hospitalization, and follow-up year.

Fine Particulate Air Pollution and Cardiorespiratory Effects in the Elderly

Past studies of air pollution effects among sensitive subgroups have produced inconsistent results. Our objective was to determine relationships between various measures of air pollution and cardiorespiratory effects in older subjects. We conducted a study that included repeated measurements of pulmonary function (arterial oxygen saturation) and cardiac function (heart rate and blood pressure) in a panel of 88 subjects (>57 years of age) in Seattle during the years 1999 to 2001. Subjects were healthy or had lung or heart disease. Each subject participated in sessions of 10 consecutive days of exposure monitoring and collection of health outcomes for up to 2 sessions. Associations between health outcomes and indoor, outdoor, and personal measures of particulate matter </=2.5 micrometers (PM2.5) or particulate matter </=10 micrometers (PM10) were evaluated using generalized estimating equations with an exchangeable working correlation matrix and robust standard errors. The model included terms for the within-subject, within-session effect; the within- subject, between-session effect; and an interaction term for medication usage. The model controlled for temperature, relative humidity, body mass index, and age. Associations between air pollution and health measurements were found primarily in healthy subjects. Healthy subjects taking no medications had decreases in heart rate associated with indoor and outdoor PM2.5 and PM10. Healthy subjects on medication had small increases in systolic blood pressure associated with indoor PM2.5 and outdoor PM10. Heterogeneity analysis found differences among the health groups for associations with particulate air pollution in heart rate but not in blood pressure. Modest concentrations of air pollutants were associated with small changes in cardiac function.