Over the past decades, prosthetic hip joints have improved the quality oflife for many patients. The most common complications are aseptic biornechanical failures and prosthetic joint infections. For prosthetic hip joints, delayed low-grade infections are seen most often and they are also most difficult to distinguish from aseptic mechanical failures. A prospective study was conducted to campare inilammatory markers in patients diagnosed with aseptic or septic prosthetic loosenffig. The diagnostic criteria were based on the decisions of experienced orthoperlic surgeons and microbiological analys is of periprosthetic tissue samplestaken perioperatively. Coagulase-negative staphylococci were the most common pathogens in the infected patients. Pre- or perioperative results for C-reactive protein and erytlu-ocyte sedimentation rate were valuable tools for diagnosing most, hut not all, low virulence infections. White blood cell count in synavial fluid was an important marker of infection, which was not the case for lactate. Levels of the cytokines turnor necrosis factor-α, interleukin-1 ß. and interleukin-6 in synavial fluid were significantly higher in the infected group. Patterus of inilammatory cell infiltration in periprosthetic tissue differed significantly between the groups, and infiltration of polymorphonuclear cells proved to be the best marker of distinguish between septic and aseptic loosenffig. Treatment and outcome are described for the infected patients.

To evaluate current serological criteria for Legionella pneumophila serogroup 1 (Lp1), the antibody response was prospectively studied in all patients hospitalized for Legionnaires' disease in a Swedish county during 11 y (n = 62). A 4-fold or greater rise in antibody titre to ≥ 128 (the minimum convalescent antibody level for diagnosis, as recommended by the Centers for Disease Control and Prevention), using the indirect immunofluorescence antibody test, was found in 21/52 (40%) of tested patients. By referring to the titre levels in healthy residents from the local population (World Health Organization criteria), 45/52 (87%) cases were confirmed serologically. In 21 patients followed longitudinally for 10 y, the median antibody titre fell from 256 (range 32-1024) to 16 (range 2-128) in 3 y. No booster reactions were observed in any patient. After 10 y, the geometric mean titre of this clinical cohort had reached the same level as observed in the background population 5 y earlier. Titre levels in subjects exposed to Legionella from a municipal water system indicate that only 1 out of 10 of all infections are identified clinically. Indirect immunofluorescent antibody testing with local reference sera is a sensitive method for laboratory confirmation of Lp1 in an unselected pneumonia population.