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Assessment of Laboratory Reporting to Supplement Active AIDS Surveillance -- Colorado

In January 1993, the surveillance case definition for acquired immunodeficiency syndrome (AIDS) among adolescents (aged greater than or equal to 13 years) and adults was expanded to include human immunodeficiency virus (HIV)-infected persons who have less than 200 CD4+ T-lymphocytes per uL or a CD4+ T-lymphocyte percentage of total lymphocytes less than 14 (1) or pulmonary tuberculosis, recurrent pneumonia, or invasive cervical cancer. In Colorado, laboratories are required to report positive tests for HIV antibody, and health-care providers are required to report cases of AIDS, HIV-related illness, and HIV infection. In planning for implementation of expanded AIDS surveillance criteria, the Colorado Department of Health (CDH) assessed the usefulness of laboratory reports of CD4+ T-lymphocyte test results as a supplement to existing procedures for active AIDS surveillance in Colorado. In 1993, CDH assessed tests conducted in 1992 at two of the 10 laboratories in the state that perform lymphocyte immunophenotyping. This report summarizes the results of the assessment.

Records of CD4+ T-lymphocyte tests performed at these laboratories were compared with the CDH records of persons with AIDS or HIV infection (not AIDS). For all persons who were not previously reported, CDH contacted the patient's provider or reviewed the medical record to determine whether the patient met reporting criteria. Six categories were used to classify persons tested by laboratory A or B: 1) AIDS with CD4+ T-lymphocyte count less than 200 per uL, not previously reported to CDH; 2) HIV-infected with CD4+ T-lymphocyte count greater than or equal to 200 per uL, not previously reported to CDH; 3) previously reported as HIV-infected, reclassified to AIDS, with CD4+ T-lymphocyte count less than 200 per uL; 4) previously reported as having AIDS; 5) previously reported as HIV-infected (and not reclassified to AIDS); or 6) not HIV-infected.

From January through December 1992, a total of 1161 CD4+ T-lymphocyte tests were performed at laboratory A, and 485 were performed at laboratory B. The number of persons tested by the two laboratories was 389 and 291, respectively (Table_1). Among persons tested at laboratory A, 49 (13%) with CD4+ counts less than 200 per uL were HIV positive and had not been reported previously to CDH, 40 (10%) were HIV infected with CD4+ counts greater than or equal to 200 per uL and not reported previously to CDH, and 69 (18%) were reported previously to CDH as HIV-infected and reclassified to AIDS (CD4+ counts less than 200 per uL). Among those tested at laboratory B, five (2%) with CD4+ counts less than 200 per uL were HIV positive and had not been reported previously to CDH, 14 (5%) were HIV-infected with CD4+ counts greater than or equal to 200 per uL and not reported previously to CDH, and 48 (16%) were reported previously to CDH as HIV-infected and reclassified to AIDS (CD4+ counts less than 200 per uL). Twenty-eight (7%) persons tested by laboratory A and 26 (9%) persons tested by laboratory B were tested for reasons other than HIV infection.

Most persons with AIDS or HIV infection who were identified by review of CD4+ test results but previously unreported to CDH had a diagnosis of HIV infection listed in the medical record by their physician but had no copy of a laboratory report of a positive HIV test. At laboratory A, these cases accounted for 41 (84%) of 49 newly identified AIDS cases and 36 (90%) of 40 HIV-infection (not AIDS) cases. At laboratory B, these cases accounted for four of five newly identified AIDS cases and 12 of 14 HIV-infection (not AIDS) cases.

CDH used the findings of this study to support a request that the Colorado Board of Health amend laboratory reporting regulations to include reporting of CD4+ T-lymphocyte counts less than 500 per uL (2). The resulting regulation permits laboratories to fulfill reporting requirements by permitting authorized personnel from CDH's HIV/STD Surveillance Program to review test records.

CDH maintains the records of all persons with HIV infection and AIDS, including CD4+ T-lymphocyte test results, under strict confidentiality safeguards (i.e., restricted access and alarm systems). These records may not be shared or made public on subpoena, search warrant, or discovery proceedings. Penalties for unauthorized disclosure of information are fines, imprisonment, or both. Reported by: KA Gershman, MD, BA Dahan, BF Krzywicki, HIV/STD Surveillance Program; RE Hoffman, MD, State Epidemiologist, Colorado Dept of Health. Div of HIV/AIDS, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Active case finding, including systematic contacts with hospitals, providers, and laboratories, is important to ensure timely and complete disease reporting (3). The findings in this report suggest that AIDS case ascertainment initiated by laboratory reports of CD4+ T-lymphocyte test results, with provider follow-up or medical record review, can enhance completeness of case surveillance under the 1993 case definition. Other laboratory-based approaches to enhance surveillance for AIDS-defining opportunistic infections have been effective (4).

Active surveillance at two laboratories in Colorado that perform CD4+ T-lymphocyte testing identified a substantial number of AIDS cases meeting the 1993 case definition. At laboratory A, 23% of persons with CD4+ test results had HIV infection or AIDS not previously reported to CDH, compared with 6.5% at laboratory B. The lower proportion of unreported cases at laboratory B is probably a result of active surveillance by CDH at the facility that accounts for most of the CD4+ T-lymphocyte tests performed by laboratory B. In comparison, the facility that accounts for most of the CD4+ T-lymphocyte tests performed by laboratory A relied on passive surveillance from providers.

Of these 108 previously unreported AIDS and HIV cases identified through a review of CD4+ test results at the two laboratories, 85% were based on a diagnosis of HIV infection listed in the medical record without a laboratory report of an HIV-positive test. These patients may have been tested in other states or anonymously. In the absence of CD4+ laboratory reporting, these previously unreported persons would likely remain unreported until hospitalization for an opportunistic infection or death.

The 1993 expansion of AIDS surveillance will enable health departments to monitor more effectively the extent of severe HIV-related immunosuppression and morbidity, and thus better anticipate resources required for provision of ongoing preventive and other health-care services. All states have implemented the 1993 AIDS surveillance case definition. Reporting of CD4+ T-lymphocyte counts less than 200 per uL may enhance AIDS surveillance efforts.

This report indicates how CD4+ T-lymphocyte reports enhanced surveillance completeness in Colorado. As of August 31, 1993, 17 states require laboratory-initiated reporting of CD4+ T-lymphocyte counts less than 200 per uL. Assessments of the completeness of AIDS reporting under various active surveillance methods are conducted routinely by individual states.

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. National Institutes of Health. State-of-the-art conference on azidothymidine therapy for early HIV infection. Am J Med 1990;89:335-44.

  3. Thacker SB, Berkelman RL. Public health surveillance in the United States. Epidemiol Rev 1988;10:164-90.

  4. Trino R, McAnaney J, Fife D. Laboratory-based reporting of AIDS. J Acquir Immune Defic Syndr 1993;6:1057-61.


Table_1
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TABLE 1. Classification of persons with AIDS and HIV infection based on review of
CD4+ T-lymphocyte tests at two laboratories -- Colorado, 1992
==============================================================================================
                                         Laboratory A       Laboratory B          Total
                                        --------------     --------------     --------------
Category *                              No.      (%)       No.      (%)       No.      (%)
--------------------------------------------------------------------------------------------
Previously reported as HIV-infected
  Reclassified as AIDS case +            69    ( 17.7)      48    ( 16.5)     117    ( 17.2)
  HIV infection, not AIDS &             115    ( 29.6)      95    ( 32.6)     210    ( 30.9)

Previously reported as AIDS              88    ( 22.6)     103    ( 35.4)     191    ( 28.1)

Not previously reported
  New AIDS case +                        49    ( 12.6)       5    (  1.7)      54    (  7.9)
  New HIV infection, not AIDS &          40    ( 10.3)      14    (  4.8)      54    (  7.9)

Not HIV-infected                         28    (  7.2)      26    (  8.9)      54    (  7.9)

Total persons tested                    389    (100.0)     291    (100.0)     680    (100.0)
--------------------------------------------------------------------------------------------
* Mutually exclusive categories.
+ Under 1993 AIDS surveillance case definition.
& CD4+ T-lymphocyte count >=200 per uL or CD4+ T-lymphocyte percentage >=14.
==============================================================================================


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