Synovial fluid cultures had consistent positivity, organism profiles during transport time
Click Here to Manage Email Alerts
Key takeaways:
- Synovial fluid samples with 2 to 3 days of transport had a marginally higher mean rate of culture positivity.
- Samples transported in 1 day had the same proportion of bacteria as samples transported in 5 days.
LAS VEGAS — Synovial fluid cultures had consistent positivity and organism profiles for at least 1 to 6 days of transport time to the laboratory, according to results presented at the American Academy of Orthopaedic Surgeons Annual Meeting.
“In synovial fluid acquis, it looks like the organisms stay good for culture for over several days,” Carl A. Deirmengian, MD, FAAOS, said in his presentation here. “Nevertheless, we advocate for the shortest possible transport time as the best practice.”
Deirmengian and colleagues retrospectively reviewed data for 147,246 synovial fluid samples from knee and hip arthroplasties from 2,932 different institutions in the United States that were submitted for laboratory testing. Researchers calculated transport time as days from the sample aspiration date to synovial fluid testing date, and the study included samples with a transport time of 1 to 6 days. Researchers evaluated the overall culture positivity and the proportion of major organism genera as a function of transportation time.
“When we looked at the transport times, the vast majority of samples came within 24 hours of collection, 72%, and 0.4% came after Day 6 or on Day 6,” Deirmengian said. “So, we’re seeing an exponential decrease in samples as days go on, and that makes sense because surgeons are sending us their samples as soon as possible.”
Deirmengian noted samples transported in 1 day had about the same culture positivity rate as samples transported in 4 to 5 days, while samples with 2 to 3 days of transport had a marginally higher mean rate of culture positivity. When it comes to alpha-defensin positive samples, Deirmengian noted no differences in culture positivity rate among transport days 1 through 5.
“There is a trend toward decrease at day 6, but hardly any of the samples are transported over 6 days,” Deirmengian said. “I don’t think any of us would say it’s OK to have a sample in the mail for 6 days, so it’s an irrelevant time point, but that’s where we start to see a drop off in culture results.”
He added samples transported in 1 day had the same proportion of bacteria as samples transported in 5 days.
“It’s not like we’re seeing pseudomonas at Day 4 suddenly all die or all of these false positives,” Deirmengian said. “We see quite good stability over 5 days.”
Collapse
Deirmengian CA, et al. Paper 410. Presented at: American Academy of Orthopaedic Surgeons Annual Meeting; March 7-11, 2023; Las Vegas.
Click Here to Manage Email Alerts