Diagnosis of human hydatidosis - Predictive value of a rural ultrasonographic survey in an apparently healthy population

The usefulness of ultrasonography (US) in the early diagnosis of hydatidosi s, applied in large-scale surveys to populations lacking clinical symptoms of the disease, has been amply documented. However, the rate of false posit ive and negative results is poorly described. Due to this, the present pape r is aimed to evaluate the sensitivity, specificity and predictive value of a conventional rural ultrasonographic survey in comparison with higher ima ging complexity. Accordingly, during 1997 and 1998 a total of 1054 children from 7 to 14 years of age were evaluated by means of US, in the town of In geniero Jacobacci, Province of Rio Negro, Argentina, employing a portable d evice for population studies. All detected cases were referred to a high co mplexity center specialized in imaging diagnosis for their re-evaluation wi th US, CT scanning and X-rays. A control group comprising 3 children negati ve by US for each positive case in the mass screening survey was selected a nd reexamined by US and X-rays and CT scanning in doubtful situations. Twen ty-seven asymptomatic carriers were referred with images compatible with hy datid cysts, while 66 were classified as disease free. At reexamination, 24 of those diagnosed as carriers and the totality of those classified as hea lthy were confirmed. On the basis of our results, a sensitivity of 100%, a specificity of 95.6% and a global test value of 96.7% were estimated.