Session Information
Session Type: ACR Poster Session B
Session Time: 9:00AM-11:00AM
Background/Purpose:
Septic arthritis (SA) is one of the emergencies in rheumatology. This pathology is more common due to the increased usage of artificial joints. Culture is the “gold standard” for diagnosis of the disease which in many cases is quite obscure, due to nonspecific clinical symptoms and laboratory results. Optimal treatment of this condition depends on timely and accurate culture report. A major goal is to optimize the essential culture method. Different essays suggested adding Bactec™, a blood culture system (BC), to the basic conventional culture (CC). The original culture is based on an agar plate being a platform for growth of bacteria. The organism is identified and analyzed regarding sensitivity to different antibiotics. The instrumented blood culture systems are based on media that permits screening for microorganisms present in blood allowing growth of microorganisms that may not occur with conventional media. This greater recovery leads to more accurate diagnosis and effective treatment, which can in turn lead to shorter hospital stays, lower patient costs, and greater overall laboratory and institutional efficiency. However the cost is increased and the false positive rate may increase leading to unnecessary antibiotic treatment.
The aim of this study is to evaluate cases where both methods were used regarding a possible added value of operating both methods.
Methods:
After obtaining ethical permission we assessed consecutive synovial fluid samples submitted to the microbiology laboratory. Samples that had been submitted in both methods i.e. CC and BC were included in the cohort. All cases with a positive result by either method were reviewed for clinical and demographic data. Specimens were defined as contamination when there was an alternative infectious diagnosis, when the white cell count was lower than 50,000 and in most cases of coagulase negative staphylococcus. Data was analyzed regarding sensitivity, specificity, and positive and negative predictive values (PPV, NPV).
Results:
1024 samples were reviewed, 803 of them showed no growth by either method. 221 cultures were positive, 67 by BC method only and 73 on by CC method, and 81 of the samples positive by both methods. All cases were reviewed regarding the clinical diagnosis. Cases were considered as having SA when there were clinical signs of joint infection and no other source of infection was found. Most of these cases had more than 50,000/µl leukocytes in the synovial fluid. 225 cases were defined clinically as septic arthritis. The sensitivity, specificity, positive and negative predictive values are shown in the following table.
|
|
Sensitivity |
Specificity |
PPV |
NPV |
|
Blood Culture (BC) |
.50 (.45 – .54) |
.95 (.94 – .96) |
.76 (.69 – .82) |
.87 (.86 – .88) |
|
Conventional Culture (CC) |
.42 (.37 – .47) |
.92 (.91 – .94) |
.62 (.55 – .69) |
.85 (.83 – .86) |
|
Both |
.60 (.55 – .65) |
.89 (.88 – .90) |
.62 (.56 – .65) |
.89 (.87 – .90) |
Conclusion:
BC carries better sensitivity, specificity, positive and negative predictive values in comparison to CC. It should be considered as the preferred method for synovial culture in cases when SA is suspected. The added value of co-culture with CC is relatively low.
To cite this abstract in AMA style:
Natsheh A, Cohen D, Ben Chetrit E, Nesher G, Breuer GS. Synovial Fluid Culture: Comparison of Two Culture Methods [abstract]. Arthritis Rheumatol. 2018; 70 (suppl 9). https://acrabstracts.org/abstract/synovial-fluid-culture-comparison-of-two-culture-methods/. Accessed .« Back to 2018 ACR/ARHP Annual Meeting
ACR Meeting Abstracts - https://acrabstracts.org/abstract/synovial-fluid-culture-comparison-of-two-culture-methods/