Imaging infection and inflammation in an African environment: comparison of 99Tcm-HMPAO-labelled leukocytes and 67Ga-citrate.

A considerable segment of the population of South Africa has a disease spectrum similar to those of the industrialized countries. However, a much larger proportion of its inhabitants comes from historically disadvantaged communities and is plagued by diseases typical of the developing world. Infectious diseases head the list as a cause of mortality in certain age groups. We have studied 108 patients presenting with a wide array of infections. Fifty-eight patients were examined with 67Ga-citrate and with 99Tcm-HMPAO-labelled leukocytes, 40 with leukocytes alone and 10 who had a high pre-test probability of tuberculosis with 67Ga only. The sensitivity and specificity of 99Tcm-labelled leukocyte scintigraphy in the 58 patients who had both studies were 89 and 84%, respectively, while the corresponding values for 67Ga scintigraphy were 81 and 74%, respectively. The overall sensitivity and specificity for 99Tcm-labelled leukocytes for detecting inflammatory sites in all 98 cases were 92 and 89%, respectively. Although labelled leukocytes were the better of the two agents for the early diagnosis of infections with a high probability of neutrophil infiltration, 67Ga remains an excellent alternative. It is the first choice in patients in whom tuberculosis or a neoplastic process is suspected as a cause of fever. It is also safer to use in areas where labelling of leukocytes is inadvisable because of inadequate sterility or where the risk is high of infecting other patients or staff with HIV.