Changes over time in post-seroconversion CD4 cell counts in the Italian HIV-Seroconversion Study: 1985-2002.

OBJECTIVE: To determine whether there has been a tendency for early post-seroconversion CD4 cell counts to change over calendar time. DESIGN: A prospective cohort study of individuals with well-estimated dates of seroconversion. METHODS: We studied 1251 individuals who seroconverted to HIV in Italy between 1985 and 2002, and for whom the first CD4 count was measured within 2 years of seroconversion and before any use of antiretrovirals. Linear regression models were used to assess evidence for a trend in post-seroconversion CD4 cell count over time. RESULTS: The median post-seroconversion CD4 cell count was 674 x 10 cells/l in those seroconverting between 1985 and 1990, 588 x 10 cells/l for 1991 to 1994, 559 x 10 cells/l for 1995 to 1998 and 494 x 10 cells/l for 1999 to 2002. The post-seroconversion CD4 cell count decreased by an average of 8.4 x 10 cells/l per year (95% confidence interval, 4.0-12.9; P < 0.001), after adjustment for potential confounders, including interval between HIV-negative and HIV-positive tests, lag time for first CD4 cell count measurement, age at seroconversion, gender, HIV-transmission group, and clinical centre. The finding was consistent in sensitivity analyses restricted to those with information on acute infection. CONCLUSION: These data suggest a possible decreasing trend in CD4 cell count immediately following seroconversion in Italy which requires further investigation.