       Document 0270
 DOCN  MMWR0270
 TI    Update: Trends in AIDS Diagnosis and Reporting Under the
       Expanded Surveillance Definition for Adolescents and Adults --
       United States, 1993
 DT    941118
 SO    MMWR - November 18, 1994; Vol. 43, No. 45
 AV    U.S. Government Printing Office, Superintendent of Documents,
       Washington, DC, 20402-9371, (202) 783-3238. U.S. Department of
       Commerce, National Technical Information Service, 5285 Port
       Royal Rd., Springfield, VA, 22161, (703) 487-4650.
 DE    Surveillance.  Statistics.  Epidemiology.
 TX    The expansion of the surveillance case definition for acquired
       immunodeficiency syndrome (AIDS) in January 1993 (1) resulted
       in a large increase in reported AIDS cases. This increase has
       primarily reflected reports of human immunodeficiency virus
       (HIV)-infected persons in whom severe immunosuppression (CD4+
       count less than 200 T- lymphocytes/uL or a CD4+ T-lymphocyte
       percentage of total lymphocytes of less than 14) had been
       diagnosed, which typically occurs before the onset of
       AIDS-defining opportunistic illnesses (AIDS-OIs, CDC clinical
       category C disease) (1,2). The inclusion of the CD4+ reporting
       criteria in AIDS surveillance has required an alteration in
       methods used to assess trends in AIDS incidence, previously
       based on the diagnosis of AIDS-OIs. This report first
       summarizes information about AIDS cases reported during 1993;
       then, to describe trends in AIDS incidence if the surveillance
       definition had not been expanded, this report uses estimates of
       eventual AIDS-OI diagnosis dates for persons who were reported
       with AIDS based only on the CD4+ criteria.*

       Trends in AIDS by Date of Report

       In 1993, a total of 105,990 AIDS cases were reported among
       adolescents and adults in the United States (2). Of 56,400 AIDS
       case reports based on any of the new reporting criteria (which
       include the CD4+ criteria, pulmonary tuberculosis, recurrent
       pneumonia, and invasive cervical cancer), 50,800 (90%) were
       based on the CD4+ reporting criteria; cases meeting the CD4+
       criteria represented 48% of the 105,990 total AIDS cases
       reported. The number of AIDS cases reported quarterly in 1993
       ranged from 36,290 cases (first quarter) to 18,360 cases
       (fourth quarter) (Figure 1).

       Trends in AIDS-OIs by Date of Diagnosis

       Estimating AIDS incidence based on the 1993 definition in a
       manner consistent with the definition used in previous years
       requires estimating when persons who were reported using the
       CD4+ criteria would develop AIDS-OIs. The probability
       distribution of the duration from the occurrence of a specific
       CD4+ count to the onset of the first AIDS-OI among HIV-infected
       persons was estimated using data from the CDC-sponsored
       Adult/Adolescent Spectrum of Disease Project (4). The estimated
       median time until development of an AIDS-OI for these persons
       was 19 months. The estimated AIDS-OI incidence is the sum of
       the observed AIDS-OI incidence and the incidence based on
       estimated dates of diagnosis for persons reported with AIDS
       based only on the CD4+ criteria; both incidences were adjusted
       for reporting delays.

       In 1993, the incidence of AIDS-OIs was estimated to have been
       62,000 cases, approximately 15,000 cases each quarter (Figure
       2).** The incidence in 1993 increased 3% compared with the
       estimated number of cases of AIDS-OIs (60,000) diagnosed in
       1992. However, compared with 1992, the estimated number of
       AIDS-OIs diagnosed among homosexual/bisexual men (30,300) in
       1993 decreased 1%; among persons who were injecting-drug users
       (IDUs) (17,800), it increased 8%, and among persons reported as
       infected through heterosexual contact (7500), it increased 23%.

       The estimated incidence of AIDS-OIs varied substantially by
       geographic region (Figure 3). For example, compared with 1992,
       the estimated numbers of homosexual/bisexual men diagnosed with
       AIDS-OIs in 1993 were stable in the Northeast, South, and
       Midwest and decreased in the West. Among persons who were IDUs,
       the number of AIDS-OI cases increased in the Northeast, where
       most of these persons resided when diagnosed with AIDS, but
       were similar in 1992 and 1993 in the South and West. Although
       the number of estimated AIDS-OI cases associated with
       heterosexual transmission remained lower than cases among
       homosexual/bisexual men and persons who were IDUs, the
       incidence of cases associated with heterosexual transmission
       increased in all four regions. The increase in estimated
       AIDS-OI incidence from 1992 to 1993 associated with
       heterosexual transmission ranged from 11% (South) to 39%
       (Northeast).

       The inclusion of HIV-infected persons with the three clinical
       conditions added to the surveillance definition in 1993 also
       may have contributed to the increased incidence of AIDS-OIs.
       These cases represented 4% of estimated AIDS-OIs diagnosed in
       1992 and 8% of estimated AIDS-OIs diagnosed in 1993 (CDC,
       unpublished data, 1994). However, data are insufficient to
       estimate for persons with these clinical conditions the time
       until the development of an AIDS-OI included in the pre-1993
       surveillance definition.

       Reported by: Local, state, and territorial health depts. Div of
       HIV/AIDS, National Center for Infectious Diseases, CDC.

       Editorial Note: Standard methods for examining AIDS
       surveillance data have been 1) by year of report, even though
       cases may be diagnosed in earlier years; and 2) by year of
       diagnosis, although adjustments have been necessary to account
       for delays in reporting. The analysis of AIDS surveillance data
       based on date of report provides information to immediately
       monitor the performance of surveillance efforts and enables
       rapid approximation of epidemiologic trends. Long-term trends
       in AIDS cases are reflected more closely by analyses based on
       year of diagnosis with adjustments for reporting delays. The
       expanded AIDS surveillance criteria have improved estimates of
       the number and characteristics of persons with severe HIV
       disease --particularly among populations most affected by the
       AIDS epidemic--and increased the usefulness of AIDS
       surveillance in describing HIV-related severe
       immunosuppression, morbidity, and mortality (2,6). However, the
       expansion also has complicated the interpretation of AIDS
       trends, a consequence that had been anticipated (1).

       The increase in the number of reported AIDS cases in 1993
       predominantly reflected the expansion of the surveillance
       criteria; the expansion has continued to affect reporting in
       1994. During January- September 1994, a total of 63,101 AIDS
       cases were reported, compared with 36,333 and 88,075 cases
       reported during the same periods in 1992 and 1993,
       respectively. As the impact of the expanded case definition
       continues to diminish, the number of total cases for 1994
       probably will be less than cases reported during 1993.

       Estimates of the dates of eventual AIDS-OI diagnoses for
       persons reported with AIDS based only on the CD4+ criteria are
       necessary to more accurately track trends in AIDS incidence. At
       least two factors may affect these estimates. First, reporting
       of persons with AIDS based on the CD4+ criteria who die before
       the diagnosis of an AIDS-OI would result in overestimating
       AIDS-OI diagnoses. Second, the underreporting of concurrent
       AIDS-OIs diagnosed among persons reported based on the CD4+
       criteria would result in an underestimate of the incidence of
       AIDS-OIs. However, analyses using preliminary estimates of
       unreported concurrent AIDS-OIs and probability of death before
       the development of AIDS-OIs indicate that correcting for these
       factors may increase the estimated incidence of AIDS-OIs in
       1992 and 1993 by approximately 2% and 3%, respectively. These
       estimates also may be affected by the timeliness and
       completeness of AIDS case reporting. Studies are in progress to
       evaluate AIDS case reporting using the 1993 criteria. The
       results from these studies will help to refine future estimates
       of AIDS-OI incidence.

       The changes in the incidence of AIDS-OIs reflect the evolution
       of the HIV epidemic in the United States. Overall, the epidemic
       of AIDS-OIs increased but at a slower rate than that in
       previous years. Among homosexual/bisexual men, AIDS-OI
       diagnoses have plateaued or decreased slightly. This reflects
       the rate of HIV transmission among homosexual/bisexual men,
       which peaked in the mid-1980s (7). However, male-to-male sexual
       transmission of HIV continues to occur, particularly among
       young men (8). The incidence of AIDS-OIs increased among
       persons who were IDUs and persons infected through heterosexual
       contact. As in previous years, AIDS-OI cases related to
       heterosexual transmission in 1993 showed the largest
       proportionate increases, disproportionately affected
       racial/ethnic minorities, and were closely related to the
       continued growth of the AIDS epidemic among persons who were
       IDUs (9).

       The examination of regional AIDS trends reveals differences in
       the predominant modes of HIV transmission and their relative
       growth in recent years. Because of such variations, the use of
       AIDS surveillance to develop epidemiologic profiles at the
       local level is essential to target and develop appropriate
       HIV-prevention strategies. CDC is working with state,
       territorial, and local health departments, and community
       organizations to develop HIV-prevention planning programs based
       on local epidemiologic profiles.

       References

              1. CDC. 1993 Revised classification system for HIV
       infection and expanded surveillance case definition for AIDS
       among adolescents and adults. MMWR 1992;41(no. RR-17).

              2. CDC. Update: impact of the expanded AIDS surveillance
       case definition for adolescents and adults on case
       reporting--United States, 1993. MMWR 1994;43:160-1,167-70.

              3. CDC. Revision of the CDC surveillance case definition
       for acquired immunodeficiency syndrome. MMWR 1987;36(no. 1S).

              4. Farizo KM, Buehler JW, Chamberland ME, et al.
       Spectrum of disease in persons with human immunodeficiency
       virus infection in the United States. JAMA 1992;267:1798-805.

              5. Chambers JM, Cleveland WS, Kleiner B, Tukey PA.
       Graphical methods for data analysis. Belmont, California:
       Wadsworth International Group, 1983:91-104,121-3.

              6. CDC. Assessment of laboratory reporting to supplement
       active AIDS surveillance--Colorado. MMWR 1993;42:749-52.

              7. Rosenberg PS, Gail MH. Estimating HIV prevalence and
       projecting AIDS incidence in the United States: a model that
       accounts for therapy and changes in the surveillance definition
       for AIDS. Statistics in Medicine 1992;11:1633-55.

              8. Lemp GF, Hirozawa AM, Givertz D, et al.
       Seroprevalence of HIV and risk behaviors among young homosexual
       and bisexual men: The San Francisco/Berkeley Young Men's
       Survey. JAMA 1994;272:449-54.

              9. CDC. AIDS among racial/ethnic minorities--United
       States, 1993. MMWR 1994;43:644-7,653-5.

        * Single copies of this report will be available until
          November 18, 1995, from the CDC National AIDS Clearinghouse,
          P.O. Box 6003, Rockville, MD 20849-6003; telephone (800)
          458-5231.

       ** Estimates in this report are not adjusted for incomplete
          reporting of diagnosed AIDS cases.

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