Abstract
Aim
Here we describe a cohort study to determine the performance of a commercially available Fluorescence In Situ Hybridization (FISH)-kit on samples of 65 consecutive patients suspected of orthopedic implant associated infections (IAI). Culture is routinely used and has a high specificity and sensitivity but requires days to more than a week for slow growing bacteria. FISH results are available within 45–60 minutes and thus specific treatment can start immediately. In addition, previous antibiotic therapy may hinder culture while bacteria may still be detected by FISH.
Method
The hemoFISH-kit from Miacom diagnostics (Dusseldorf, Germany) was used on a total of 82 joint aspirates, sonication fluids and tissue samples of 65 consecutive patients to detect and identify possible microorganisms. This FISH-kit contains a universal 16S rRNA probe and species-specific probes for bacteria commonly encountered in blood infections. FISH and culture were compared to the clinical definition of IAI. These definitions were based on the criteria described by Pro-Implant Foundation criteria for IAI after fracture fixation or prosthetic joint infection. If no criteria were described in the literature for a specific IAI then MSIS criteria were used.
Results
FISH and culture was done in 33 plain tissue samples, 43 sonication fluid samples and 6 joint aspirates of 65 patients. Results are shown in table 1.
In clinical infections FISH provided earlier results in 7 and 2 extra for culture-negative. In 5 IAI-negative cases FISH was false-positive.
Conclusions
Faster diagnosis by FISH is appealing, however with a PPV of 64% the hemoFISH-kit is not accurate enough for clinical use. Also, blood and orthopedic infections have different common pathogens, therefor FISH could not identify all of the bacterial strains due to a lack of specific probes. An orthopedic FISH-kit could solve this problem.
