Is ultrasonography useful for population studies on schistosomiasis mansoni? An evaluation based on a survey on a population from Kome Island, Tanzania

BACKGROUND: Observation of characteristic alterations at liver ultrasonography in clinical schistosomiasis mansoni cases has initiated utilization of this examination method in population surveys in areas where this disease is endemic. PURPOSE: To present results of liver ultrasonography and their relation to epidemiological data of a population in an area endemic for S. mansoni, to estimate the precision of classification of periportal anatomy changes known as periportal fibrosis (PPF), and to evaluate the relevance of ultrasonography in epidemiological studies on S. mansoni. MATERIAL AND METHODS: A total of 459 inhabitants on Kome Island, Lake Victoria, Tanzania were examined by ultrasound with image documentation by locally trained personnel. A subsample of this population, 116 individuals, was subject to ultrasonography by two examiners independently. Separately, the images were classified for PPF according to the Managil protocol, twice for the subsample. RESULTS: PPF could be classified for 458 individuals; 64% and 36% were classified as I or II, respectively; none was classified as 0; only one as III. Results were similar for the subsample examined twice. Comparing the two separate classifications of all 232 sets of images of the subsample gave a Kappa (K) value of 0.50. When comparing the classifications of each of the two different examinations of the same individuals of the subsample, K values of 0.29 and 0.34 for the first and second classification, respectively, were obtained. CONCLUSION: Ultrasonography does not appear to correlate well with disease stage. Presently, it should not be utilized for staging of schistosoma mansoni-related liver damage in population surveys.