Serum lactate is a better predictor of short-term mortality when stratified by C-reactive protein in adult emergency department patients hospitalized for a suspected infection

Study objective: We determine whether C-reactive protein (CRP) adds prognostic value to serum lactate levels when assessing mortality risk in emergency department (ED) patients admitted for a suspected infection.

Methods: This was an observational cohort of unique adult patients (≥ 21 years of age) who had lactate and CRP testing in the ED and were admitted for a suspected infection during a 1-year period. All data were collected through retrospective chart review. The study site is an urban teaching hospital with an approximate annual census of 95,000 patients. The endpoint was 28-day inpatient mortality.

Results: One thousand one hundred forty-three patients had lactate and CRP testing in the ED, an admitting diagnosis of infection, and complete records. Twenty-eight-day inpatient mortality for patients with both a lactate level greater than or equal to 4.0 mmol/L and CRP level greater than 10.0 mg/dL was 44.0% (95% confidence interval [CI] 32.5% to 55.5%), for lactate greater than or equal to 4.0 mmol/L and CRP less than or equal to 10.0 mg/dL, it was 9.7% (95% CI 2.7% to 16.7%), and for lactate level less than 4.0 mmol/L, it was 9.1% (95% CI 7.3% to 10.9%). In a logistic regression model that included patient demographics and Charlson score, as well as 4 separate dichotomous variables that were positive only in subjects with (1) serum lactate greater than or equal to 4.0 mmol/L and CRP level greater than 10.0 mg/dL, (2) lactate level greater than or equal to 4.0 mmol/L and CRP level less than or equal to 10.0 mg/dL, (3) lactate level less than 4.0 mmol/L and CRP level greater than 10.0 mg/dL, and (4) lactate level less than 4.0 mmol/L and CRP level less than or equal to 10.0 mg/dL (as reference), patients with both a lactate level greater than or equal to 4.0 mmol/L and CRP greater than 10 mg/dL had an increased risk of 28-day inpatient mortality (odds ratio 12.3; 95% CI 6.8 to 22.3).

Conclusion: In this cohort, patients with both an increased CRP level and hyperlactatemia had a higher mortality rate than patients with abnormalities of either laboratory test in isolation.