Alpha-Defensin and Synovial Proteins to Improve Detection of Pediatric Septic Arthritis

The purpose of this study is to determine if alpha-defensin and other proteins present in
joint fluid may be able to rapidly diagnose bacterial joint infections. Patients with
suspected joint infection typically undergo joint aspiration so that tests can be performed
to help diagnose joint infection, including gram stain, cell count, and culture. Patients
under 18 years old that are undergoing sampling of their joint fluid due to suspicion of
infection or inflammation will be enrolled in this multi-center trial. Joint fluid will also
be sampled from normative controls made up of patients who are undergoing an unrelated
procedure without inflammation or infection. Joint fluid from patients with suspected
inflammation/infection and from normative controls will be analysed for presence of
alpha-defensin, leukocyte esterase, neutrophil elastase, synovial C-reactive protein, and
synovial lactate. The alpha-defensin assay has shown high sensitivity and specificity for
joint infection in other studies. Additionally a Staphylococcus spp antigen panel, Candida
spp antigen panel, Enterococcus faecalis assay, BACTAlert culture, cell count plus
differential, gram stain, and aerobic, anaerobic, and fungal cultures will be done using
synovial fluid. A synovial fluid PCR for Kingella kingae will be performed if the patient is
under eight years of age. Blood tests will include cell count and differential, erythrocyte
sedimentation rate, C-reactive protein, procalcitonin, and D-dimer, as well as relevant
inflammatory or rheumatologic marker tests. Results from these tests will be compared to
joint fluid culture which the gold standard for diagnosing bacterial infection. The study
includes 1 visit per patient, the standard of care visit in which the patient would be
undergoing joint aspiration or arthroscopy. Once data has been collected, the sensitivity and
specificity will be determined for these experimental tests both individually and in
combination.

Inclusion Criteria- Septic Cases and Inflamed, Non-Septic Comparators:

- Synovial fluid is obtained to assess for infection or inflammatory/rheumatologic
disease (all medium and large joints will be included: hip, knee, ankle, shoulder,
subtalar, elbow, and wrist joints)

- Patients with recent antibiotic exposure are eligible to participate but will be
analyzed separately

Inclusion Criteria- Normative Controls:

- Patients undergoing a procedure unrelated to infection (the procedure may be
arthroscopy, or an open or percutaneous bony or soft tissue procedure)

Exclusion Criteria- All Participants:

- Family declines to participate/consent

- Patients with a major joint trauma (such as a documented ligament tear or fracture)
within the past 8 weeks are not eligible to have that joint aspirated, but could have
another joint aspirated

Exclusion Criteria- Normative Controls:

- A history of recent infection (within the past 3 months)

- Received antibiotics in the past 7 days