The classification of AIDS cases: concordance between two AIDS surveillance systems in Italy

This study assessed the concordance between the transmission classification of 725 acquired immunodeficiency syndrome (AIDS) cases by the Italian AIDS Registry (the national surveillance system) and the classification of the same cases by the Italian Cooperative Group on AIDS-Related Tumors. A high degree of concordance emerged for intravenous drug users in both sexes (kappa = 0.88; 95% confidence interval [CI] = 0.84, 0.92), for homosexual men (kappa = 0.83; 95% CI = 0.79, 0.87), and for persons infected through contaminated blood or blood derivatives (kappa = 1.00). The concordance was lower among heterosexual men (kappa = 0.51; 95% CI = 0.37, 0.65) and especially among men whose risk group was not determined (kappa = 0.28; 95% CI = 0.12, 0.44). The discrepancies observed among heterosexual men indicate a need for continuing and accurate monitoring of AIDS reporting by transmission category.