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Preventive therapies delay the onset of some opportunistic diseases in HIV patients

Opportunistic diseases are common complications of HIV infection, but the incidence rates of secondary Pneumocystis carinii pneumonia (PCP), cryptococcal meningitis, and herpes zoster have declined in the past 5 years, and they are being diagnosed at a later stage of HIV disease (lower median CD4 cell count). In addition, the incidence rates of primary PCP and Kaposi sarcoma also appear to be declining compared with historical estimates.

These improvements are due to the effective use of antiretroviral therapy, targeted preventive therapy, and more comprehensive clinical management of the disease, according to a study supported by the Agency for Health Care Policy and Research through its pharmaceutical outcomes research program (HS07809). The study was led by Johns Hopkins University School of Medicine researchers, Richard D. Moore, M.D., M.H.Sc., and Richard E. Chaisson, M.D.

They estimated the probability of developing opportunistic infection and cancer, measured the number of CD4 cells at the time opportunistic disease developed and survival after its onset, and examined the association between preventive drug therapies and occurrence of opportunistic infection among 1,246 HIV-infected patients with CD4 counts of 300 or less (normal count is about 1,000) at an urban university HIV clinic from 1989 to 1995. Between the earlier period (1989-1992) and the later period (1993-1995), the incidence of several opportunistic infections decreased: cryptococcal meningitis declined from 3 to 1.4 events per 100 person-years; second-time PCP declined from 6.2 to 3.7; and herpes zoster declined from 4.2 to 2.4.

In the late 1980s, opportunistic infections typically began to appear when an HIV-infected person's CD4 lymphocyte count dropped to about 200. In this study, only infections with herpes simplex virus, tuberculosis, and herpes zoster occurred at CD4 counts greater than 100. Toxoplasmosis, progressive multifocal leukoencephalopathy, the wasting syndrome, second-time PCP, cytomegalovirus infection, and Mycobacterium avium complex bacteremia occurred at a mean CD4 count of less than 50. After adjustment for CD4 count, the use of fluconazole was associated with a decreased rate of cryptococcal meningitis and candidiasis, rifabutin use with a decreased rate of M. avium complex bacteremia, and trimethoprim-sulfamethoxazole use with a decreased rate of secondary PCP.

For more information, see "Natural history of opportunistic disease in an HIV-infected urban clinical cohort," by Drs. Moore and Chaisson, in the April 1, 1996, Annals of Internal Medicine 124(7), pp. 633-642.

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