C-reactive protein/albumin ratio predicts 90-day mortality of septic patients

Abstract

Introduction: Residual inflammation at ICU discharge may have impact upon long-term mortality. However, the significance of ongoing inflammation on mortality after ICU discharge is poorly described. C-reactive protein (CRP) and albumin are measured frequently in the ICU and exhibit opposing patterns during inflammation. Since infection is a potent trigger of inflammation, we hypothesized that CRP levels at discharge would correlate with long-term mortality in septic patients and that the CRP/albumin ratio would be a better marker of prognosis than CRP alone.

Methods: We evaluated 334 patients admitted to the ICU as a result of severe sepsis or septic shock who were discharged alive after a minimum of 72 hours in the ICU. We evaluated the performance of both CRP and CRP/albumin to predict mortality at 90 days after ICU discharge. Two multivariate logistic models were generated based on measurements at discharge: one model included CRP (Model-CRP), and the other included the CRP/albumin ratio (Model-CRP/albumin).

Results: There were 229 (67%) and 111 (33%) patients with severe sepsis and septic shock, respectively. During the 90 days of follow-up, 73 (22%) patients died. CRP/albumin ratios at admission and at discharge were associated with a poor outcome and showed greater accuracy than CRP alone at these time points (p = 0.0455 and p = 0.0438, respectively). CRP levels and the CRP/albumin ratio were independent predictors of mortality at 90 days (Model-CRP: adjusted OR 2.34, 95% CI 1.14-4.83, p = 0.021; Model-CRP/albumin: adjusted OR 2.18, 95% CI 1.10-4.67, p = 0.035). Both models showed similar accuracy (p = 0.2483). However, Model-CRP was not calibrated.

Conclusions: Residual inflammation at ICU discharge assessed using the CRP/albumin ratio is an independent risk factor for mortality at 90 days in septic patients. The use of the CRP/albumin ratio as a long-term marker of prognosis provides more consistent results than standard CRP values alone.

Figure 1. Study flowchart.

Figure 2. Plot versus criterion value curves for the CRP/albumin ratio and mortality at 90 days (Panel A) and for CRP versus 90-day mortality (Panel B).

The X-axis shows the CRP/albumin ratio (Panel A) and serum CRP levels in mg/L (Panel B). The Y-axis shows the percentage. The solid and dashed lines indicate sensitivity and specificity with 95% confidence intervals, respectively.

Figure 3. Kaplan-Meier curves showing the 90-day survival of septic patients after discharge from the intensive care unit.

Solid line, CRP/albumin ratio <2 group; dashed line, CRP/albumin ratio >2 group; triangles, censored patients.

Figure 4. Model of the probability of mortality at 90 days after ICU discharge.

The probability of death at 90 days after ICU discharge is depicted using a multivariate logistic model. In A and C, the model is depicted versus age and in B and D versus SOFA score. The models A and B include age, SOFA score, chronic comorbidities, hemoglobin levels and ICU LOS. The models C and D include all variables cited above in addition to the CRP/albumin ratio. The black and gray solid lines indicate the calculated probability of death for dead and alive patients, respectively. For young and less severe patients, the model CRP/albumin ratio (C and D) could differentiate better between survivors and non-survivors than the model without biomarkers. However, as age and SOFA score increase, both models presented similar differences between survivors and non-survivors. The lines were fitted using a loess smooth function.