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Published on: October 15, 2014
Use of Sentinel blood culture system for analysis of specimens from potentially infected prosthetic joints
1Microbiology Department, Selly Oak Hospital, Birmingham.
Abstract:
The Sentinel blood culture system was used for the analysis of 657 specimens from infected prosthetic joints and blood cultures (83 from prosthetic joints and 574 from standard blood cultures). The positivity rate was similar for specimens from prosthetic joints and blood cultures (18% compared with 14%). However, there was an unacceptable rate of false positive results with specimens from prosthetic joints (58% compared with 8%). This high false positivity rate was due to (i) prolonged incubation and (ii) the lack of blood in these specimens. It is therefore recommended that the Sentinel system should only be used for the initial seven days of incubation of specimens taken from prosthetic joints. Further incubation should take place in a standard incubator and a terminal subculture performed after 21 days.
Insights
The Sentinel blood culture system shows high false positive rates for prosthetic joint infections due to prolonged incubation. Limit its use to seven days for these specimens to improve accuracy.
Area of Science:
- Clinical microbiology
- Infectious diseases
- Prosthetic joint infections
Background:
- Prosthetic joint infections (PJIs) require accurate and timely diagnosis.
- Blood culture systems are crucial for identifying causative pathogens.
- The Sentinel system is a common method for blood culture analysis.
Purpose of the Study:
- To evaluate the performance of the Sentinel blood culture system for analyzing specimens from infected prosthetic joints.
- To compare the diagnostic yield and false positive rates of the Sentinel system for PJIs versus standard blood cultures.
Main Methods:
- Analysis of 657 specimens using the Sentinel blood culture system.
- Comparison between 83 prosthetic joint specimens and 574 standard blood culture specimens.
- Assessment of positivity rates and false positive rates.
Main Results:
- Similar positivity rates were observed for prosthetic joint specimens (18%) and standard blood cultures (14%).
- An unacceptably high false positive rate (58%) was found for prosthetic joint specimens, compared to 8% for standard blood cultures.
- Prolonged incubation and lack of blood in specimens contributed to false positives.
Conclusions:
- The Sentinel system's prolonged incubation and specimen type lead to high false positive rates in prosthetic joint infections.
- Recommendations include limiting Sentinel system use to the initial seven days for prosthetic joint specimens.
- Further incubation in a standard incubator with a terminal subculture after 21 days is advised for improved accuracy.
