Risk factors and clinical outcomes associated with blood culture contamination

Abstract

Objective: To determine patient-specific risk factors and clinical outcomes associated with contaminated blood cultures. Design: A single-center, retrospective case-control risk factor and clinical outcome analysis performed on inpatients with blood cultures collected in the emergency department, 2014–2018. Patients with contaminated blood cultures (cases) were compared to patients with negative blood cultures (controls). Setting: A 509-bed tertiary-care university hospital. Methods: Risk factors independently associated with blood-culture contamination were determined using multivariable logistic regression. The impacts of contamination on clinical outcomes were assessed using linear regression, logistic regression, and generalized linear model with γ log link. Results: Of 13,782 blood cultures, 1,504 (10.9%) true positives were excluded, leaving 1,012 (7.3%) cases and 11,266 (81.7%) controls. The following factors were independently associated with blood-culture contamination: increasing age (adjusted odds ratio [aOR], 1.01; 95% confidence interval [CI], 1.01–1.01), black race (aOR, 1.32; 95% CI, 1.15–1.51), increased body mass index (BMI; aOR, 1.01; 95% CI, 1.00–1.02), chronic obstructive pulmonary disease (aOR, 1.16; 95% CI, 1.02–1.33), paralysis (aOR 1.64; 95% CI, 1.26–2.14) and sepsis plus shock (aOR, 1.26; 95% CI, 1.07–1.49). After controlling for age, race, BMI, and sepsis, blood-culture contamination increased length of stay (LOS; β = 1.24 ± 0.24; P < .0001), length of antibiotic treatment (LOT; β = 1.01 ± 0.20; P < .001), hospital charges (β = 0.22 ± 0.03; P < .0001), acute kidney injury (AKI; aOR, 1.60; 95% CI, 1.40–1.83), echocardiogram orders (aOR, 1.51; 95% CI, 1.30–1.75) and in-hospital mortality (aOR, 1.69; 95% CI, 1.31–2.16). Conclusions: These unique risk factors identify high-risk individuals for blood-culture contamination. After controlling for confounders, contamination significantly increased LOS, LOT, hospital charges, AKI, echocardiograms, and in-hospital mortality.

The effect of the COVID-19 pandemic on the epidemiology of positive blood cultures in Swiss intensive care units: a nationwide surveillance study

“…Possible factors behind this increase include: the oversight of basic infection control practices by reallocated staff with limited or no experience in intensive care; an inadequate diligence with aseptic techniques due to ICU overcrowding; the urgency of blood sampling among critically ill patients; the implementation of ad hoc standardized protocols that envision the sampling of otherwise unneeded blood cultures; and the inexperience in wearing personal protective equipment (PPE). Contamination of blood cultures has been associated with increased antibiotic exposure, prolonged venous access, additional consultations, laboratory and diagnostic requests, prolonged hospitalizations, costs and intra-hospital mortality [ 17 , 18 ]. The increased rates of contaminated blood cultures suggest, therefore, that the challenges encountered when dealing with ICU patients during the pandemic indeed negatively affected the management of critically ill patients [ 19 ].…”

Diagnostic stewardship for blood cultures in the emergency department: A multicenter validation and prospective evaluation of a machine learning prediction tool

“…The consequent decrease in false-positive blood cultures may lead to lower resource use, shorter hospital stays, more appropriate use of antibiotics, and perhaps even lower in-hospital mortality. 9 , 12 , 13 , 14 Choosing which threshold probability for a positive culture is acceptable as a cut-off for doing or withholding a blood culture in practice depends on the physicians’ preferences and concerns about the patient. The decision curve analysis showed that our model could provide net benefits across an extensive range of cut-offs.…”

“… 3 The percentage of true-positive blood cultures, disregarding contamination, ranges from 1.4% to 12.2% in ED populations worldwide. 4 , 5 , 6 , 7 , 8 , 9 , 10 Due to these low yields, blood culture outcomes affect treatment decisions in only 0.18–2.8% of patients presenting to the ED with suspected infection. 4 , 5 …”

“…A substantial 40–55% of positive cultures can be contaminated. 5 , 6 , 8 , 9 , 12 Three decades of research on this topic has consistently shown that contamination is associated with additional resource use (laboratory and microbiological testing), increased use of antibiotics, prolonged hospital stay, and even increased in-hospital mortality. 9 , 12 , 13 , 14 …”

A Continuous Late-Onset Sepsis Prediction Algorithm for Preterm Infants using Multimodal Physiological Signals from a Patient Monitor

“…Timely diagnosis of LOS and starting antibiotic therapy lower the mortality of LOS [5]. However, the current gold standard for diagnosing LOS is based on the results of blood culture analysis which takes more than 24 hours to obtain the results [6]. Therefore, in clinical practice, the antibiotic therapy starts at the moment of blood culture ordering (often denoted as a Cultures, Resuscitation, and Antibiotics Started Here (CRASH) moment), based on the clinical signs of infection, even though these clinical signs may be nonspecific and inconspicuous [2].…”