Serum uric acid: a forgotten prognostic marker in acute coronary syndromes?

BACKGROUND

Serum uric acid (UA) has been shown to be an independent predictor of outcome in the general population and in patients with heart failure. There are, however, limited data regarding the prognostic value of UA in the context of acute coronary syndromes (ACS) particularly in medium-term follow up and the available results are contradictory.

MATERIALS AND METHODS

Study of consecutive patients admitted with an ACS (with and without ST-segment elevation) at a single-centre coronary care unit. Primary endpoint was all-cause mortality at 1-year follow up. We evaluated if serum UA is an independent predictor of outcome and if it has any added value on top of GRACE risk score for risk prediction.

RESULTS

We included 683 patients, mean age 64±13 years, 69% males. In-hospital and 1-year mortality were 4.5 and 7.6% respectively. The best cut-off of UA to predict 1-year mortality was 6.25 mg/dl (sensitivity 59%, specificity 72%) and 30.2% of the patients had an increased UA according to this cut off. Independent predictors of UA were male gender (β= 0.078), body mass index (β=0.163), diuretics before admission (β=0.142), and admission serum creatinine (β=0.403). One-year mortality was significantly higher in patients with increased UA (15.5 vs. 4.2%, p<0.001; log rank, p<0.001). After adjustment, both increased UA as a categorical variable (HR 2.25, 95% CI 1.23-4.13, p=0.008) and as a continuous variable (HR 1.26, 95% CI 1.13-1.41, p<0.001) are independent predictors of mortality. The AUC increases only slightly after inclusion of UA in the model with GRACE risk score (from 0.78 to 0.79, p=0.350). Both models had a good fit; however, model fit worsened after inclusion of UA. Overall, the inclusion of UA in the original was associated with an improvement in both the net reclassification improvement (continuous NRI=44%), and the integrated discrimination improvement (IDI=0.052) suggesting effective reclassification.

CONCLUSIONS

Serum UA is an independent predictor of all-cause mortality in medium-term after the whole spectrum of ACS and has an added value for risk stratification.