COMPARISON OF TECHNETIUM 99M NANOCOLLOID AND INDIUM 111 LEUKOCYTES IN THE DIAGNOSIS OF ORTHOPEDIC INFECTIONS

It has been suggested that technetium 99m nanocolloid is as effective an inflammatory radiopharmaceutical as indium 111 leucocytes. This study compares the efficacy of Tc-99m nanocolloid and In-111 leucocytes in the detection of orthopaedic infection in 19 patients with a high clinical suspicion of infection. The two scintigrams were performed within 24 h of each other. A scintigram was considered positive where there was an increase in tracer uptake at the site of interest. Concordance rate of 73% was achieved. The numbers of false positives with In-111 leucocytes and Tc-99m nanocolloid were three and six respectively. The single false negative in both was of a patient with tuberculous spondylodiscitis. Sensitivity was 75% in both. Specificities were 79% and 60% for In-111 leucocytes and Tc-99m nanocolloid respectively. Positive Predictive Value was only 33% with Tc-99m nanocolloid and 50% with In-111 leucocytes. Tc-99m nanocolloid also proved less reliable in accurately detecting infected prostheses. We conclude that Tc-99m nanocolloid cannot replace In-111 leucocytes in the diagnosis of orthopaedic infections.