Biomarkers that might improve prognostic accuracy in ICU patients

Introduction

There is often a discrepancy between physician prediction of mortality and clinical prediction scores, and the accuracy of the latter is rather moderate. Nevertheless, it is tempting to just measure a biochemical parameter – a biomarker – to find prognostic information. Serum lipoproteins, for example, can mirror inflammatory activity and prognosis as well.

Methods

A prospective study of 29 patients that stayed in the ICU for at least 4 days and had the following characteristics: age 62.28 ± 16.92 years, length of stay in the ICU 15.55 ± 10.51 days and APACHE II score 21.28 ± 7.83. C-reactive protein (CRP), total cholesterol and high-density lipoprotein (HDL) were measured on admission and on day 4 in the ICU. First, we correlated these parameters with the length of stay in the ICU using Pearson's correlation method. Secondly, we compared the means between survivors and nonsurvivors after 6 months with an independent-samples' t test. We finally performed receiver operating curves of the above parameters according to mortality.

Results

CRP both on admission and on day 4 was positively correlated with length of stay in the ICU (P < 0.05). Mortality in 6 months was 18/29 (62%). According to the independent-samples' t test, statistical significance (P < 0.05) was only found for CRP on admission. On admission, the values of areas under the curve (AUC) were: CRP = 0.793, HDL = 0.667, total cholesterol = 0.604. Furthermore, on day 4 the values of AUC were: CRP = 0.629, HDL = 0.712 and cholesterol = 0.629. Using a cutoff CRP value on admission of ≤ 0.87 mg/dl, there was a better chance of survival with a sensitivity of 63.6% and a specificity of 94.44% (95% CI = 72.6–99.1). In addition to that, a cutoff HDL value on day 4 of ≥ 28.4 mg/dl predicts survival with a sensitivity of 63.6% and a specificity of 83.3% (95% CI = 46.5–90.2).

Conclusion

Serial measurements of CRP and HDL are both easy to perform and can add prognostic information. On the other hand, total cholesterol seems not to have any prognostic significance.