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Negative BACTEC 460-TB cultures. How long to incubate?
American Journal of Clinical Pathology
|August 1, 1988
Summary
Current mycobacterial culture guidelines recommend eight weeks of incubation. However, this study found that 98.8% of Mycobacterium isolates were detected within five weeks using the BACTEC TB system, suggesting shorter incubation periods may be cost-effective.
Area of Science:
- Medical Microbiology
- Clinical Diagnostics
- Infectious Diseases
Background:
- Standard mycobacterial culture protocols mandate an eight-week incubation period.
- Optimizing diagnostic timelines and resource allocation in clinical microbiology is crucial.
Purpose of the Study:
- To evaluate the clinical relevance and cost-effectiveness of extended incubation periods for mycobacterial cultures using the BACTEC TB system.
- To determine if the current eight-week incubation guideline is necessary for the BACTEC TB system.
Main Methods:
- Retrospective review of 3,662 specimens cultured over 30 months using the BACTEC TB system.
- Analysis of isolate detection rates at different incubation time points (four and five weeks).
- Estimation of additional costs associated with prolonged incubation, including labor.
Main Results:
- 96.8% of Mycobacterium isolates were detected by week four, and 98.8% by week five.
- Extended incubation beyond five weeks incurred an estimated cost of $1,016.20 for 92 hours of labor.
- Only one of four late-occurring isolates showed potential clinical significance.
Conclusions:
- The standard eight-week incubation guideline for mycobacterial cultures, particularly with the BACTEC TB system, warrants review.
- Incubation beyond five weeks for BACTEC TB cultures may not be clinically relevant or cost-effective.
- Reducing incubation time could lead to significant cost savings and resource optimization.