Impact of the 1987 revised AIDS case definition in Denmark: a follow-up study 2 years after its adoption

We present a follow-up study on Danish AIDS patients notified according to the latest revision of the AIDS case definition during the first 2 years after its adoption. A total of 271 adult AIDS cases were notified in the period of study (Jan. 1, 1988-Dec. 31, 1989). 60 patients (22%) met only the revised AIDS case definition and of these 17 patients (28%) developed diseases meeting the old AIDS case definition. Thus, AIDS reporting increased by 28% due to the change in case definition, the impact being 19% after adjusting for patients developing old case diseases. No time trend in the impact was found. We estimated the cumulative percent of cases meeting the new case definition who subsequently will develop diseases meeting the old definition as 15% after 6 months and 51% after 18 months. The revision produced a disproportionate increase in reporting of female cases (p less than 0.05), transfusion cases (p less than 0.01) and to a lesser extent of heterosexual cases, while the impact on reporting of homo/bisexual men showed a decrease (p less than 0.01). Cases notified with new case definition diseases were older than cases notified with old diseases. Among patients meeting only the new case definition, 25 died and 18 (30%) had not developed old case diseases before death. We found no difference in survival rates between patients within the 2 groups of case definition. Among patients meeting the new definition we found no differences in HIV antigenemia or CD4 cell count between those developing diseases meeting old case definition and those who did not.