Review Question - QID 219543

C-reactive protein is a hepatic-produced acute phase reactant that aids in complement activation.

Wound & hardware infection is the most common complication following orthopedic trauma surgery and is a significant source of patient morbidity. Diagnosis can be made clinically with the presence of incisional erythema, dehiscence, purulent drainage and/or persistent fracture nonunion or hardware loosening on radiographs. Intraoperative deep cultures are the most reliable method to isolate causative organisms. Treatment is usually surgical irrigation and debridement followed by culture-directed antibiotics. Hardware removal may be performed acutely or in a delayed fashion, depending on fracture healing.

Govaert et al. reviewed fracture-related infection (FRI). They summarized the available evidence and provided recommendations for the diagnosis of FRI. They concluded that the FRI consensus definition together with a proposal for an update based on the available evidence relating to the diagnostic value of clinical parameters, serum inflammatory markers, imaging modalities, tissue and sonication fluid sampling, molecular biology techniques, and histopathological examination. Second, recommendations on microbiology specimen sampling and laboratory operating procedures relevant to FRI were provided.

Lee et al. performed a systematic review and meta-analysis to evaluate the diagnostic accuracy of synovial fluid biomarkers and to determine which test has the highest diagnostic odds ratio (DOR) for the diagnosis of PJI. They reported that synovial fluid leukocyte count, PMN%, CRP, α-defensin, LE, IL-6, and IL-8 all demonstrated high sensitivity for diagnosing PJI, with α-defensin being the best synovial marker based on the highest log DOR. They concluded that other synovial fluid tests that demonstrate good diagnostic performance can also be used in combination for the diagnosis of PJI.

Incorrect Answers:
Answer 1: Erythrocyte sedimentation rate (ESR) is often part of the laboratory evaluation for surgical site and fracture-related infections. Circulating acute phase reactants cause a change in the negative surface charge of erythrocytes resulting in an increase in agglutination and formation of stacks of erythrocytes known as rouleaux. The result is an increase in the ESR measured value.
Answer 3: Platelets are produced in bone marrow also considered an acute phase reactant and are increased during states of inflammation.
Answer 4: Polymorphonucleocyte percentage is helpful in interpreting synovial fluid analysis when diagnosing joint infection. PMNs are also produced in the bone marrow.
Answer 5: Macrophage percentage is not a routine reference laboratory marker.