[AIDS patients with an unclassified risk factor for HIV]

In the surveillance of the AIDS epidemic via registries there is a small proportion of cases whose route of HIV transmission is unknown (5% for Catalonia, Spain). For reclassification purposes, the aim of this study is to detect similarities between these cases with "not qualified risk" (NQR) with the other main HIV transmission groups.

All Aids cases (> 12 years) resident in Catalonia and reported between 1988 and 1996 to the AIDS registry (n = 8,559) were compared according to their distribution of "age at diagnosis" and "first indicative AIDS disease". ANOVA and log-linear regression models were applied separately by sex.

Evidence of similarity with the NQR group was only found for men; in terms of age at diagnosis, the NQR group was similar to both groups of sexual transmission whilst in terms of Aids indicative disease it was similar to the heterosexual transmission group. As from 1994, a reduction in the incidence of NQR cases was observed and coincided with an increase in the heterosexual group.

According to the characteristics of the NQR cases, it can be concluded that all cases acquired HIV via one of the classic routes of infection, primarily through heterosexual contacts. For this reason, it is advisable that the criteria that define heterosexual HIV transmission be relaxed.