Does elevated procalcitonin (PCT) predict infection in an inflamed joint?

From the Guidelines

Raised procalcitonin is not a reliable predictor of infection in inflamed joints, and its use is not recommended as a standalone diagnostic tool for this purpose. The provided evidence does not support the use of procalcitonin for predicting infection in inflamed joints, instead highlighting the importance of other markers such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) in diagnosing periprosthetic joint infection 1.

Key Points to Consider

• CRP has been shown to have a sensitivity of 73% to 91% and specificity of 81% to 86% for the diagnosis of prosthetic knee infection when a cutoff of 13.5 mg/L or more is used 1
• The combination of CRP and ESR has been found to be a useful tool for diagnosing infection, with abnormal results for at least two of three tests (CRP, ESR, and fibrinogen) leading to accurate results for the diagnosis of infection (sensitivity, 93%; specificity, 100%; accuracy, 97%) 1
• Joint aspiration has been found to be extremely useful in diagnosing joint infection after total knee arthroplasty (TKA), with a sensitivity, specificity, and accuracy of 100% in some studies 1
• The use of alpha-defensin laboratory test has been described for the diagnosis of periprosthetic joint infection, with high accuracy and sensitivity 1

Clinical Implications

• When evaluating a patient with a suspected infected inflamed joint, it is essential to consider a combination of clinical findings, laboratory tests, and imaging studies to make an accurate diagnosis
• CRP and ESR should be used as initial screening tools, with joint aspiration and alpha-defensin testing considered for further evaluation if necessary
• Procalcitonin should not be relied upon as a sole diagnostic tool for infection in inflamed joints, due to its limitations and potential for false negatives and false positives.

From the Research

Raised Procalcitonin and Infection in Inflamed Joint

• Raised procalcitonin (PCT) levels have been found to be a sensitive and specific marker of infection in patients with an inflamed joint 2.
• PCT is a biomarker that is preferentially induced in patients with bacterial infections, and its measurement can be a useful addition to a rheumatologist's repertoire 2.
• Several studies have examined the use of PCT to assist in the differentiation between septic and non-septic arthritis in patients with an inflamed joint, and found it to be a reliable marker of infection 2, 3.

Diagnostic Role of Procalcitonin

• Procalcitonin has been shown to be a useful biomarker for the early detection of postoperative infections in open fractures, with elevated preoperative PCT levels predicting infection 3.
• PCT can help differentiate bacterial from non-bacterial infections and inflammation states, particularly in respiratory illness 4.
• The use of PCT-guided antibiotic stewardship has been found to reduce antibiotic exposure and associated side-effects among patients with respiratory infection and sepsis 4.

Clinical Practice Guidelines

• Clinical practice guidelines have endorsed the use of procalcitonin in the differential diagnosis of bacterial infections and/or to monitor antibiotic therapy 5.
• However, the evidence for or against the use of procalcitonin is weak, and further studies are needed to validate its use in clinical practice 5.
• PCT levels may help guide the need for empirical antibiotic therapy, source control for infections, and duration of antibiotic therapy 6.