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Three Part Question

In [adult patients] what is the [likelihood of detecting a significant bacteraemia] by [collecting blood specimens for culture at the time that a patient is febrile]?

Clinical Scenario

The standard practice to increase the likelihood of yielding a positive blood culture is to obtain blood specimens at or around the time of a temperature spike. This is based on the principle that the presence of organisms in the intravascular space leads to the elaboration of cytokines, causing body temperatures to rise. In clinical practice this is not always possible, so I want to determine whether it is necessary to obtain blood sample for culture when a patient is febrile.

Search Strategy

Pub Med and Medline search.
Using keywords 'Blood culture', 'Timing' and 'Collection'.

Search Outcome

Only one relevant article was found

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Riedel S et al. April 2008 USA	Adults 18 years of age and older	Multi-centre study based on retrospective reviews of medical records, evaluating timing of blood culture collection in relation to temperature elevations in 1436 patients with bacteraemia and fungaemia.	Patients	67% men, 33% women. Average age 58.9 years (range 18 to 97)	This study only looked at timing of collection samples with temperature elevations in patients who had a positive blood culture. It would have been useful to compare this cohort with patients who had negative blood cultures.
			The time of obtaining the first significant blood culture from a patient was defined as time of index positive blood culture (T-IPBC). Three temperatures recorded in the patients notes were noted: highest temp during the 24 hour period prior to T-IPBC, temperature closest to T-IPBC and highest temp recorded after the T-IPBC. Tmax was determined as the highest of the three temperatures and defined as time of maximum concentration of organism in serum.	A total of 3937 temperatures were recorded within +/- 24 hours of T-IPBC. In 9.6% of patients, a temperature was recorded at the same time the IPBC was obtained. No one time interval between temperature spikes and collection of IPBC consistently yielded the highest proportion of Tmax, thereby suggesting that it is not necessary to collect blood culture at the time that adult patients are experiencing a temperature elevation as a means for optimizing the detection of bacteraemia.
			Temperature associations were also analysed according to specific organism recovered from IPBC, patient age, gender and WCC. The three time periods were >24 to 1hr prior to IPBC, 1h before to 1h after, and 1 to 24 hrs after the IPBC.	No statistically significant associations were noted among the different organism groups. No statistically significant associations between temperature spikes and patient gender, age or WCC.

Clinical Bottom Line

Although there is limited data on this subject, the conclusion I have drawn is that to optimise the detection of significant bacteraemia it is not necessary to time collection of blood culture specimin with the patient's temperature. More important factors would be adequate volume of blood, aseptic technique and repeating samples if necessary.

References

1. Stefan Riedel Timing of Specimin Collection for Blood Cultures from Febrile Patients with Bacteremia Journal of Clinical Microbiology April 2008. p1381-1385