Septic Arthritis

Septic Arthritis and Septic KneeNew Test for Rapid Diagnosis of Septic Arthritis

There is a new and more accurate way to get a quick and inexpensive highly accurate test result on patients with septic arthritis, or a septic knee. The combined use of leukocyte esterase and glucose region strips can give a very quick and accurate diagnosis a septic arthritis.

This excellent study was published in the December issue of the Journal of Bone and Joint Surgery, American version, 2014. The research group was from the trauma department of the Hanover Medical School in Hanover, Germany. Mohamed Omar, M.D. was the lead author of the paper.

Leukocyte esterase is an enzyme secreted by neutrophils, and it is clearly increased in the inflammatory process. A reduce glucose concentration in the infected joint is also present because the bacteria will feed on the glucose. The combination of 1) identification of leukocyte esterase from the bacteria and 2) a reduced glucose level, strongly suggest an infected joint. It helps to quickly differentiate between the septic and aseptic inflammatory process in the joint in a real-time manner at a relatively inexpensive cost.

Prior to the findings in this study, the joint fluid would need to be sent to the microbiology lab and analyzed under the microscope to determine whether or not crystals are present within the joint fluid. This can take time, and results can vary depending on the staff available to read the slides in the microbiology lab.

This insightful study has recommended doing these two very simple inexpensive tests right in the doctor’s office or the emergency department to help differentiate between a septic arthritis and aseptic inflammatory process of the joint. It is still recommended that the joint be aspirated and fluid be sent for further analysis to the laboratory to obtain: 1) a Gram stain, 2) culture results, and 3) sensitivity results.

The combination of using the glucose strips and the leukocyte esterase test is a very quick screening test that can be completed in real-time fashion at a relatively low cost with accurate results.

The authors of the article pointed out that most healthcare providers would state that a synovial fluid count of greater than 50,000 cells per mm3 with a neutrophil percentage of greater than 75% is specific for septic arthritis. However others have reported that those cut off values failed to reliably differentiate between septic arthritis and other types of inflammatory arthritis. Using the glucose test in the leukocyte esterase test would give a quick and reliable answer.

The authors also noted that the availability of synovial fluid leukocyte and crystal analysis is limited, especially in primary and secondary care settings. If technical and personnel requirements can be met, the procedure takes approximately 60 to 90 minutes. In addition, the analysis must be done soon after arthrocentesis because a synovial fluid leukocyte count can decrease within a few hours.