Synovial Fluid culture

Sample type:

Synovial fluid

Uses:

• Culture of the synovial fluid or of synovial tissue itself is the only definitive method of diagnosing septic arthritis.

• Synovial fluid analysis is a key component of the minimum database needed to diagnose and manage primary

• and secondary articular joint disorders.

Precautions:

• If possible, stopping antibiotics for 4 days and holding cultures for 14 days may increase the yield.

• In addition, sonication of removed prosthetic material appears to increase the sensitivity of culture, especially in patients who have received antibiotics before surgery.

• Routine sterile technique should be followed for all arthrocentesis procedures,

• Fluid should be left in the sterile syringe and/or placed into an aerobic culturette or blood culture tube

Interfering factors

• Culture results in patients with nongonococcal septic arthritis are almost always positive.

• Check if the patient has received antibiotics before the joint aspiration.

• Cultures of the joint fluid in gonococcal infections yield positive results in only about 25% of cases.

Pre Analytical errors

Clotting can occur with significant hemorrhage or blood contamination. It is recommended to aliquot a portion of the sample into (EDTA) tube to prevent coagulation and allow for additional analyses.

Corrective action:

The smallest EDTA blood tube available should be used to avoid erroneous results due to sample dilution from excess anticoagulant. If small tubes are not available, then excess EDTA can be decanted from the vessel before adding the sample.

Post-analytical errors:

• Not all requested tests done

• Uncontrolled results