Research Article: Value of routine blood tests for prediction of mortality risk in hip fracture patients

Date Published: February 8, 2012

Publisher: Informa Healthcare

Author(s): Mathias Mosfeldt, Ole B Pedersen, Troels Riis, Henning O Worm, Susanne van Mark, Henrik L Jørgensen, Benn R Duus, Jes B Lauritzen.

http://doi.org/10.3109/17453674.2011.652883

Abstract

There is a 5- to 8-fold increased risk of mortality during the first 3 months after a hip fracture. Several risk factors are known. We studied the predictive value (for mortality) of routine blood tests taken on admission.

792 hip fracture patients were included prospectively; blood tests were taken on admission. Follow-up data on mortality were obtained from the civil registration system. Patients were divided into 2 groups based on whether they had survived at least 90 days after the hip fracture. To estimate which laboratory tests could be used to predict outcome, we used receiver operation characteristic (ROC) curves.

3-month mortality could be predicted with 69% accuracy from the level of plasma creatinine in standard admission blood tests. The mortality in patients with elevated levels of creatinine was almost 3-fold that of the patients with normal creatinine. Mortality was also associated with age, low blood hemoglobin, high plasma potassium, and low plasma albumin levels.

Our findings could be of use in identifying patients who might benefit from increased attention perioperatively.

Partial Text

792 hip fracture patients aged 60 or older who were admitted to the Department of Orthopedics, Bispebjerg University Hospital, Denmark from October 2008 through July 2010 were included prospectively. 67 patients aged less than 60 were excluded. Follow-up data on mortality were obtained from the civil registration system on August 1, 2010. Patients were included in the study within the first 3 days after admission.

232 of 792 patients (29%) died during the study period (Table 1), at median 44 (1–582) days. 57 died between 1 and 66 days, while still in hospital. 106 died after leaving hospital but within 3 months, and 69 died some time after 3 months. Based on the ROC curves (Figure 1), the cutoff values were set at 7 mmol/L in both sexes for hemoglobin and above 50 mg/L for C-reactive protein (CRP). The ROC curves for most other laboratory tests did not indicate any optimal cutoff value (the number of correctly classified patients was the same for a large variety of values) (Table 2). We therefore decided to use the upper or lower limits of normal laboratory reference intervals as cutoff values.

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 prospective observational study of 2,963 consecutive patients by Lewis et al. (2006). They found that serum urea was an independent 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 potassium, 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 admission was a risk factor for poor 4-month survival. Using multiple logistic regression analysis, creatinine was not found to be an independent risk factor (Björkelund et al. 2009).

 

Source:

http://doi.org/10.3109/17453674.2011.652883