Early participation in an HIV cohort study slows disease progression and improves survival

Background, Different levels of experience of physicians caring for patient s with HIV infection have been found to be associated with differences in s urvival amongst their patients, We examined whether early participation in the Swiss HIV Cohort Study (SHCS), an ongoing prospective study with regula r follow-up visits at specialized clinics, improved survival of HIV-infecte d patients. Methods, We studied 3553 HSV-infected individuals who joined the Swiss HIV Cohort Study (SHCS) with different levels of immunosuppression: mild (CD4 c ount above 500 x 10(6) cells L-1; n x 2038); severe (100-199 cells; n = 960 ); and very severe (50-99 cells; n = 555). Characteristics at different CD4 cell levels were compared and Cox proportional hazards regression was used to examine the mortality experience during a total of 16 201 person-years of followup. Results. Participants joining the cohort early with mild immunodeficiency w ere younger, more likely to be female, and more likely to have a history of intravenous drug use. At CD4 cell counts below 200 x 10(6) cells L-1, they were less likely to have a history of Pneumocystis carinii pneumonia or AI DS, more likely to be on prophylaxis against P. carinii and more likely to be on antiretroviral therapy than those joining with severe or very severe immunodeficiency, For example, at the time of the first CD4 cell count in t he range of 50-99 x 10(6) cells L-1, 8.9, 15.0 and 21.6% of participants wh o joined with mild, severe and very severe immunodeficiency had suffered an episode of P. carinii pneumonia. In Cox models adjusted for CD4 cell count at entry and other relevant baseline differences, mortality was increased amongst participants who joined with severe and very severe immunodeficienc y. Hazard ratios (95% confidence intervals (CI)) were 1.71 (1.21-2.42) for participants with severe immunodeficiency at entry and 2.61 (1.70-4.01) for those with very severe immunodeficiency, compared with 1.0 for those with mild immunodeficiency at entry Conclusions. Individuals who were seen regularly at specialized HIV units f rom early stages of the infection onwards were, at comparable levels of imm unodeficiency, less likely to progress to AIDS, and mortality during subseq uent follow-up was reduced. This is likely to be explained by better access to prophylactic regimens and antiretroviral therapy.