Acta Orthopaedica 2012; 83 (1): 31–35 33 Figure 1. ROC curves for prediction of mortality in relation to labo- ratory values at admission. The curves represent plasma creatinine (crea, solid line), inverse blood hemoglobin (hb, dashed line), and plasma potassium (K, dotted line). Hemoglobin values were converted because the association with death followed decreasing values. Table 2. Area under the curve (AUC) for the routine laboratory tests included in the study Area under ROC a Plasma creatinine Plasma potassium Blood hemoglobin Plasma albumin Blood platelet count Plasma CRP Blood glucose Blood leukocyte count Plasma sodium a Receiver operating curve b standard error 0.69 0.61 0.60 0.59 0.58 0.55 0.52 0.52 0.51 SE b 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 95% CI 0.64–0.74 0.55–0.66 0.55–0.65 0.53–0.64 0.53–0.63 0.50–0.60 0.47–0.57 0.47–0.57 0.46–0.56 count, or CRP. After adjustment in the multivariate logistic regression model, age, plasma creatinine, plasma potassium, plasma albumin remained as risk factors. Discussion Previous studies on mortality after hip fracture have found an association with plasma creatinine levels (Lewis et al. 2006, Singh et al. 2008, Björkelund et al. 2009, Bennet et al. 2010, Ho et al. 2010), which is what we found in the present study. Of these previous studies, the most comprehensive was a pro- spective observational study of 2,963 consecutive patients by Lewis et al. (2006). They found that serum urea was an inde- pendent predictor of mortality at 30 and 90 days, and also at 1 and 2 years. Furthermore, mortality was also higher in patients admitted with raised or low serum sodium, raised serum potas- sium, and raised serum creatinine. A prospective cohort study of 436 patients in Sweden found that in bivariate analysis, a creatinine concentration of more than 100 umol/L on admis- sion was a risk factor for poor 4-month survival. Using mul- tiple logistic regression analysis, creatinine was not found to be an independent risk factor (Björkelund et al. 2009). In both of the above-mentioned studies, the cutoff value for elevated creatinine was set differently than in our study, and it appears that the same value was used for both sexes. In our study, the cutoff level for elevated serum creatinine was set at 105 μmol/L for men and 90 μmol/L for women, as these are the upper limits of 95% CI in normal Scandinavian subjects (Felding et al. 2004). A recent Norwegian study on 364 hip fracture patients found that the use of diuretics, followed by the presence of conges- tive heart disease on admission, were the strongest predictors of 1-year mortality (Juliebø et al. 2010). These findings sug- gest that the increased mortality in patients with elevated cre- Figure 2. Kaplan Meier plot: mortality in relation to creatinine levels at admission. 3-month mortality after hip fracture. The plot on the left is divided into groups with elevated plasma creatinine (dotted line) and normal plasma creatinine (solid line). Plasma creatinine was elevated if above 105 μmol/L in males and 90 μmol/L in females. The plot on the right is divided into quartiles of plasma creatinine.