Guidelines for Complications of Cancer Treatment Vol VIII Part B

FDG-PET scanning had a positive predictive value of 80%and a negative predictive value of 98.5% for the diagnosis ofinfection at the site of total hip arthroplasty when increaseduptake around the stem-bone interface was used as the criterionfor infection. With further research, this new and promisingmodality may have an important role in the diagnosis ofperiprosthetic infection.Culture of aspirated fluid from around the joint should beconfirmatory for infection. However, contamination can reducethe value of this test. The predictive value of a positive cultureof aspirated fluid will be higher if the test is used to confirmrather than to screen for infection 42 .Besides microbiologic testing, aspirated joint fluid also canbe analyzed with respect to cell count and differentials.Spangehl et al. reported that a leukocyte count of >50 × 103cells/ìL combined with a neutrophil percentage of >80% washighly suggestive of infection 43 . A recent study demonstratedthat a joint fluid leukocyte count of 1700 cells/L yielded apositive predictive value of 73% and negative predictive valueof 98%, whereas a neutrophil percentage of ?65% yielded apositive predictive value of 94% and negative predictive valueof 99% 44 . A more recent study 42 showed that a fluid whiteblood-cell count cutoff value of 1760 cells/L yielded a 99%positive predictive value and an 88% negative predictive value.However, the cutoff value of their neutrophil percentage wasslightly higher (73%) and had a similar positive predictivevalue (96%) but had a slightly lower negative predictive value(91%).References1. Cannon SR. Massive prostheses for malignant bonetumours of the limbs. J Bone Joint Surg Br. 1997;79:497–506.116