Can We Reduce Negative Blood Cultures With Clinical Scores and Blood Markers? Results From an Observational Cohort Study

Abstract

Only a small proportion of blood cultures routinely performed in emergency department (ED) patients is positive. Multiple clinical scores and biomarkers have previously been examined for their ability to predict bacteremia. Conclusive clinical validation of these scores and biomarkers is essential.This observational cohort study included patients with suspected infection who had blood culture sampling at ED admission. We assessed 5 clinical scores and admission concentrations of procalcitonin (PCT), C-reactive protein (CRP), lymphocyte and white blood cell counts, the neutrophil-lymphocyte count ratio (NLCR), and the red blood cell distribution width (RDW). Two independent physicians assessed true blood culture positivity. We used logistic regression models with area under the curve (AUC) analysis.Of 1083 patients, 104 (9.6%) had positive blood cultures. Of the clinical scores, the Shapiro score performed best (AUC 0.729). The best biomarkers were PCT (AUC 0.803) and NLCR (AUC 0.700). Combining the Shapiro score with PCT levels significantly increased the AUC to 0.827. Limiting blood cultures only to patients with either a Shapiro score of ≥4 or PCT > 0.1 μg/L would reduce negative sampling by 20.2% while still identifying 100% of positive cultures. Similarly, a Shapiro score ≥3 or PCT >0.25 μg/L would reduce cultures by 41.7% and still identify 96.1% of positive blood cultures.Combination of the Shapiro score with admission levels of PCT can help reduce unnecessary blood cultures with minimal false negative rates.The study was registered on January 9, 2013 at the ‘ClinicalTrials.gov’ registration web site (NCT01768494).

Procalcitonin-guided diagnosis and antibiotic stewardship revisited

“…Blood cultures give important information about the type of microorganism and its susceptibility to antibiotic treatment. However, only a small proportion of cultures give positive results and 40–90% remain negative [17, 19]. A large retrospective study from China found that only 440 of 2829 blood cultures (15.5%) were positive [20].…”

“…One observational cohort study from 2015 that included 1083 patients who had blood culture drawn in the emergency department investigated several clinical scores and blood biomarkers, including the ability of PCT to predict blood culture sampling [19]. In blood culture-positive cases (N = 104, 9.6%) the Shapiro score and initial PCT concentration performed best, with AUCs of 0.729 and 0.803, respectively.…”

Biomarkers of Infection: Are They Useful in the ICU?

“…However, only a small proportion of cultures turn positive and in 40 to 90% of patients with a suspected systematic infection, the culture does not grow any pathogens. 9,10 For example, a large retrospective study from China found that of 2,829 blood cultures taken upon hospital admission, only 440 (15.5%) came back positive. 11 Further limitations of blood cultures include a long time to result, which in turn limits initial treatment decision making and contamination resulting in suboptimal specificity of results.…”

Personalized medicine of patients with respiratory infections through the measurement of specific blood biomarkers: fact or fiction?

“…Studies between 1996 and 2011 were included and showed a good high discriminatory ability of PCT (area under the curve of 0.85), with pooled sensitivity and specificity of 0.77 and 0.79, respectively [9]. Observational data for pneumonia and general emergency patients with positive blood culture as the gold standard have shown similar results in regard to discrimination [10,11]. More important than observational studies are interventional trials evaluating whether a marker has a positive effect on patient outcomes.…”