Results
Mean age of the study population was 63.7 ± 13.1 years, and 524 patients (70.1%) were male. Median ACEF-MDRD score in the study population was 2.43 (1.73 - 3.74), and median ACEF-MDRD score in the study groups were 1.51 (1.29 - 1.73), 2.41 (2.13 - 2.80) and 4.60 (3.74 - 5.77), respectively. 142 patients (19.0%) were dead at the end of the one-year follow up.
Demographic, anthropometric, clinical and laboratory characteristics of the patients were summarized in Tables 1 and 2. As expected, there were significant differences across groups in terms of characteristics. Patients within the ACEF-MDRDhigh group were more likely to be older and male as compared to ACEF-MDRDlow group, and patients within the ACEF-MDRDhigh group are more likely to be symptomatic, with lower functional capacity. Besides having a higher creatinine and lower glomerular filtration rate at baseline; hemoglobin and albumin were significantly lower and NT-proBNP was significantly higher in ACEF-MDRDhigh group. Finally, both the frequency of patients with at least one hospitalization and the total number of repeat hospitalizations were more frequent in the ACEF-MDRDhigh group, and mortality was significantly higher in the latter group compared to both ACEF-MDRDmedand ACEF-MDRDlow (Bonferroni-corrected p-value <0.001 for both pairwise comparisons) (Figure 1).
Kaplan-Meier curves for one-year survival and cumulative hazards for study groups were provided in Figure 2. There were significant differences between the ACEF-MDRD tertiles in terms of one-year survival (log-rank p<0.001). On pairwise comparisons, patients within the ACEFhigh tertile had a significantly lower one-year survival as compared to ACEF-MDRDlow and ACEF-MDRDmed groups (p<0.001). There was also a trend towards lower survival in the ACEF-MDRDmed group as compared to ACEF-MDRDlow group, but this was not statistically significant (p=0.08).
Univariate and multivariate predictors of mortality were provided in Table 3. After adjustment, each one-point increase in the ACEF-MDRD score was associated with a 14% (95%CI: 4% - 24%) increase in one-year mortality. In addition to ACEF-MDRD, other parameters that were associated with mortality were the presence of congestive symptoms at admission, lower sodium and higher NYHA class.
ACEF-MDRD had an overall c-statistic of 0.66 ± 0.03 for prediction of one-year mortality, and for a cut-off point of 2.71, it had a sensitivity of 71.1%, specificity of 61.9%, positive predictive value of 30.1% and negative predictive value of 90.1%. All component variables of ACEF-MDRD had a lower c-statistic for predicting one-year mortality as compared to ACEF-MDRD (age: 0.62 ± 0.03, left ventricular ejection fraction: 0.64 ± 0.03, glomerular filtration rate: 0.56 ± 0.03, overall p=0.001).
On a multivariate regression model consisting of ACEF-MDRD and GWTG-HF score, both scores were found as independent predictors of one-year mortality (OR:1.08 (95%CI:1.05 - 1.11), p<0.001 for GWTG-HF score and OR:1.12 (95%CI: 1.02 - 1.23), p=0.02 for ACEF-MDRD). For predicting one-year mortality, GWTG-HF score had a c-statistic of 0.70 ± 0.02, and the difference between GWTG-HF score and ACEF-MDRD was not statistically different (p=0.14) (Figure 3). Overall NRI was 0.107, indicating an improvement of prediction of mortality with ACEF-MDRD score over GWTG-HF score. Individual components of the NRI analyses have shown that correct prediction of one-year mortality was slightly inferior with ACEF-MDRD (NRIe -0.023) but prediction of survival was much better when ACEF-MDRD was used (NRIne 0.130).