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

It has been suggested that technetium 99m nanocolloid is as effective an inflammatory radiopharmaceutical as indium 111 leucocytes. This stu dy compares the efficacy of Tc-99m nanocolloid and In-111 leucocytes i n the detection of orthopaedic infection in 19 patients with a high cl inical suspicion of infection. The two scintigrams were performed with in 24 h of each other. A scintigram was considered positive where ther e was an increase in tracer uptake at the site of interest. Concordanc e rate of 73% was achieved. The numbers of false positives with In-111 leucocytes and Tc-99m nanocolloid were three and six respectively. Th e single false negative in both was of a patient with tuberculous spon dylodiscitis. Sensitivity was 75% in both. Specificities were 79% and 60% for In-111 leucocytes and Tc-99m nanocolloid respectively. Positiv e Predictive Value was only 33% with Tc-99m nanocolloid and 50% with I n-111 leucocytes. Tc-99m nanocolloid also proved less reliable in accu rately detecting infected prostheses. We conclude that Tc-99m nanocoll oid cannot replace In-111 leucocytes in the diagnosis of orthopaedic i nfections.