Core IM | Internal Medicine Podcast #50 Blood Cultures: Mind the Gap Segment
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Oct 2, 2019 Dive into the fascinating world of blood cultures! Discover the guidelines for accurate testing and the surprising rates of false positives. Explore which clinical signs suggest positive blood cultures and their association with infections like bacteremia. Learn about the impact of blood cultures on patient outcomes and resource utilization. The discussion balances humor with critical insights into effective fever management and the complexities of diagnosing serious infections, highlighting the need for judicious testing practices.
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Only Test When Infection Is Suspected
- Don't order blood cultures or other infection tests unless the patient has signs or symptoms of infection.
- Tests can be falsely positive and lead to overdiagnosis and overtreatment.
Low Overall Yield; Higher In Specific Risks
- Only about 7% of hospitalized patients who get blood cultures have bacteremia, rising to ~15% in high-risk groups.
- High-risk features included IV drug use, rigors, fever >38.3°C, fatal rapidly disease, acute abdomen, or major comorbidity.
Fever, Rigors, And SIRS Modify Probability
- Fever >100.9°F modestly increases the likelihood of bacteremia (LR ~2.0).
- Rigors and ≥2 SIRS criteria increase probability, but SIRS is sensitive and not very specific.