Utility of peripheral venous blood cultures in patients with central venous catheters

Clinical decision rule for obtaining peripheral blood cultures in febrile oncology patients

BACKGROUND

The utility of peripheral blood cultures in pediatric oncology patients presenting with fever is controversial. A recent systematic review showed that about one in 40 bloodstream infections (BSIs) would be missed if only central venous line (CVL) cultures are obtained.

OBJECTIVE

To derive a clinical decision rule for obtaining peripheral blood cultures in pediatric oncology patients presenting to a pediatric emergency department (PED) with fever and a CVL.

DESIGN/METHOD

A retrospective chart review was performed on pediatric oncology patients referred to the PED for fever while on therapy. Logistic regression with a random intercept was used to determine independent predictors of BSI and generate a prediction model for obtaining peripheral blood cultures. The decision rule was generated from the best performance as measured by a receiver operator curve. Bootstrapping analysis was performed for internal validation.

RESULTS

Predictors that were significant and independently associated with positive peripheral blood cultures included vasopressor support (odds ratio [OR] 16.5, 95% confidence interval [CI]: 2.80-97.71), acute myeloid leukemia (AML) diagnosis (OR 6.9, 95% CI: 1.81-25.98), hypotension (OR 4.0, 95% CI: 1.05-15.17), mucositis (OR 8.2, 95% CI: 2.48-27.01), and maximum temperature in PED ≥39°C (OR 6.6, 95% CI: 2.36-18.20). The area under the curve (AUC) for this model was 0.90 (95% CI: 0.82-0.97) in the derivation cohort and 0.90 (95% CI: 0.81-0.98) after the internal validation.

CONCLUSIONS

We derived a clinical prediction model for deciding when to obtain peripheral blood cultures in febrile oncology patients with CVLs on active therapy. Future studies should focus on prospective and external validation of this diagnostic prediction tool.

How many sources should be cultured for the diagnosis of a blood stream infection in children with cancer?

Blood stream infection (BSI) in a child with cancer is a life-threatening condition while blood cultures (BCs) play a crucial role for the diagnosis. The current practice of obtaining a BC from all sources--peripheral vein, central venous catheter (CVC), all lumens--is controversial and therefore in this study, our aim was to evaluate the utility of obtaining BCs from all these available sources. A retrospective study of BC sets obtained from all newly diagnosed patients with malignancy was conducted. A total number of 633 BC sets from 123 boys and 88 girls (median age: 5 5/12 years) were evaluated during infection episodes from January 1, 2005, to August 31, 2010. Among these cases, 134 were classified as true BSI (21%), 468 as non-BSI, and 31 as false-positive. In 64 cases, the results from peripheral and CVC sources were discordant: 57 catheter positive-peripheral negative and seven catheter negative-peripheral positive. Consequently, seven out of 134 true BSIs (5.2%) would not have been identified if only a BC from a CVC had been obtained. Moreover, if no BCs from all lumens had been obtained we would have missed up to 25% of true-positive BSIs. In the same way, if BCs from all sources had not been drawn we would not have detected up to 52% of true-positive BSIs.

CONCLUSION

Obtaining BCs during an infection episode from all sources in a child with cancer is still mandatory.