Can synovial fluid sitting out at room temperature skew diagnostic test results?

From the Guidelines

Yes, synovial fluid sitting at room temperature can significantly skew diagnostic test results. Synovial fluid should be processed promptly or properly stored to maintain its diagnostic integrity. When left at room temperature, several changes occur that affect test accuracy:

• white blood cells begin to degrade within 1-2 hours, causing falsely low cell counts;
• crystals may dissolve or form artifactually, potentially leading to missed gout or pseudogout diagnoses;
• glucose levels decrease due to cellular metabolism; and
• bacterial viability changes, potentially causing false-negative cultures in infection cases. For accurate results, synovial fluid should be analyzed within 1 hour of collection or appropriately preserved—cell counts and crystal analysis samples should be collected in EDTA tubes, culture specimens in appropriate culture media, and biochemical tests in heparinized tubes. If immediate processing isn't possible, refrigeration at 4°C can preserve most components for up to 24 hours, though this isn't ideal for crystal analysis. These timing and storage considerations are crucial because treatment decisions for conditions like septic arthritis, gout, or inflammatory arthropathies depend on accurate synovial fluid analysis 1.

Key Considerations for Synovial Fluid Handling

• Prompt processing or proper storage is essential to maintain diagnostic integrity.
• Refrigeration at 4°C can preserve most components for up to 24 hours.
• Immediate analysis or appropriate preservation in specific tubes (EDTA for cell counts and crystal analysis, culture media for cultures, and heparinized tubes for biochemical tests) is recommended.

Importance of Accurate Synovial Fluid Analysis

• Treatment decisions for septic arthritis, gout, or inflammatory arthropathies depend on accurate results.
• Inaccurate results can lead to misdiagnosis, delayed diagnosis, or inappropriate treatment, potentially resulting in longer hospitalization, increased morbidity, and mortality 1.

Given the provided evidence and the importance of accurate diagnosis for patient outcomes, it is crucial to handle synovial fluid with care and process it promptly to avoid skewing diagnostic test results.

From the Research

Impact of Room Temperature on Synovial Fluid

• Synovial fluid sitting out at room temperature can indeed skew diagnostic test results, as evidenced by a study published in 1989 2.
• The study found that the leukocyte count in synovial fluid samples decreased significantly within a few hours when stored at room temperature, which can lead to misdiagnosis of borderline inflammatory fluids.
• Additionally, calcium pyrophosphate dihydrate (CPPD) crystals were found to dissolve completely in synovial fluid samples within 3-8 weeks when stored at room temperature, which can result in missing CPPD crystals that are present in the sample.
• The study also noted that new, artifactual crystals can develop in synovial fluid samples over time when stored at room temperature, which can lead to over-interpretation of the findings.

Diagnostic Value of Synovial Fluid Analysis

• Synovial fluid analysis is a valuable diagnostic tool for joint disease, particularly in cases of acute arthritis where septic arthritis or crystal arthropathy is suspected 3, 4.
• The analysis can provide a prompt and definite diagnosis of crystal-induced arthritis, and can assist in honing the differential diagnosis of non-crystalline arthritis.
• However, the quality control of synovial fluid analysis is sparse, and tests for sensitivity, specificity, and reliability have shown worrying variations 4.

Storage and Handling of Synovial Fluid Samples

• The storage and handling of synovial fluid samples can affect the accuracy of diagnostic test results, as evidenced by the study published in 1989 2.
• The study highlights the importance of prompt examination of synovial fluid samples to avoid the problems of misdiagnosing borderline inflammatory fluids, missing CPPD crystals, or over-interpreting the findings due to artifactual crystals.
• Other studies have also emphasized the importance of proper storage and handling of synovial fluid samples, including the use of blood culture bottles (Bactec system) for microbiological identification 5.