A painful replacement and a single biomarker

A patient with a joint replacement presents with pain and declining function. An aspirate biomarker result is positive, and a trainee describes the test as perfectly diagnostic because an older study reported high accuracy. The clinician reviews the time course, examination, imaging, microbiological findings and the complete applicable diagnostic framework. Infection is important, but loosening, instability, fracture and other causes also need consideration. The next management decision may be substantial, and it cannot be made solely from a promotional sensitivity figure. The patient wants a clear explanation of what is known, what remains uncertain and why additional assessment is appropriate. Local resources, organism evidence and patient factors will affect any eventual treatment strategy.