Comparing estimates of influenza-associated hospitalization and death among adults with congestive heart failure based on how influenza season is defined

<p>Abstract</p> <p>Background</p> <p>There is little consensus about how the influenza season should be defined in studies that assess influenza-attributable risk. The objective of this study was to compare estimates of influenza-associated risk in a defined clinical population using four different methods of defining the influenza season.</p> <p>Methods</p> <p>Using the Studies of Left Ventricular Dysfunction (SOLVD) clinical database and national influenza surveillance data from 1986–87 to 1990–91, four definitions were used to assess influenza-associated risk: (a) three-week moving average of positive influenza isolates is at least 5%, (b) three-week moving average of positive influenza isolates is at least 10%, (c) first and last positive influenza isolate are identified, and (d) 5% of total number of positive isolates for the season are obtained. The clinical data were from adults aged 21 to 80 with physician-diagnosed congestive heart failure. All-cause hospitalization and all-cause mortality during the influenza seasons and non-influenza seasons were compared using four definitions of the influenza season. Incidence analyses and Cox regression were used to assess the effect of exposure to influenza season on all-cause hospitalization and death using all four definitions.</p> <p>Results</p> <p>There was a higher risk of hospitalization associated with the influenza season, regardless of how the start and stop of the influenza season was defined. The adjusted risk of hospitalization was 8 to 10 percent higher during the influenza season compared to the non-influenza season when the different definitions were used. However, exposure to influenza was not consistently associated with higher risk of death when all definitions were used. When the 5% moving average and first/last positive isolate definitions were used, exposure to influenza was associated with a higher risk of death compared to non-exposure in this clinical population (adjusted hazard ratios [HR], 1.16; 95% confidence interval [CI], 1.04 to 1.29 and adjusted HR, 1.19; 95% CI, 1.06 to 1.33, respectively).</p> <p>Conclusion</p> <p>Estimates of influenza-attributable risk may vary depending on how influenza season is defined and the outcome being assessed.</p

Predicting mortality among a community-based sample of older people with heart failure.

Objective: To identify factors available to general practitioners (GPs) that are predictive of mortality within a general practice-based population of heart failure patients, and to report the sensitivity and specificity of prognostic information from GPs. Methods: Five hundred and forty-two heart failure patients aged >60 years were recruited from 16 UK GP surgeries. Patients completed quality-of-life and services use questionnaires every 3 months for 24 months or until death. Factors with independent significant association with survival were identified using Cox proportional hazards regression analysis. Results: Women had a 58% lower risk of death. Patients self-reporting New York Heart Association Classification III or IV had an 81% higher risk of death. Patients aged 85+ years had over a five-fold risk of death as compared with those aged <65 years. Patients with a co-morbidity of cancer had a 78% higher risk of death. Of the 14 patients who died in a 12-month period, the GPs identified 11 (sensitivity 79%). They identified 133 of the 217 who did not die (specificity 61%). Discussion: Predictors readily available to GPs, such as patient characteristics, are easy to adapt to use in general practice, where most heart failure patients are diagnosed and treated. Identifying factors likely to influence death is useful in primary care, as this can initiate discussion about end-of-life care