CDC NATIONAL AIDS HOTLINE TRAINING BULLETIN #53 - May 28, 1993
Centers for Disease Control and Prevention

1. "Please compare both the 1986 and 1993 Revised HIV Classification System to Walter Reed and other major classification systems."

The three systems differ markedly in both laboratory and clinical criteria. We suggest that callers who have been classified under the Walter Reed HIV infection system and who have questions about CDC's HIV classification system be sent a copy of the CDC 1993 revised HIV classification system. Their infectious disease physician or AIDS/HIV consultant or state health department AIDS/HIV program should be able to respond to specific questions. The 1986 CDC HIV classification system is no longer valid.

2. Can a diagnosis of AIDS be made based on a T4 cell count, even if there is a negative antibody test?

No, unless certain definitively diagnosed AIDS indicator diseases are present. HIV infection must be present along with CD4 cell counts (percentages or absolute counts) indicative of severe immunosuppression before a person is included as a case reportable under the expanded CDC surveillance case definition for AIDS. Page 2 of the December 18, 1992, MMWR, entitled "1993 revised classification system for HIV infection and expanded surveillance case definition for AIDS among adolescents and adults," has a footnote which gives the criteria for HIV infection for adults and adolescents. Please note that immunosuppression can be caused by other diseases or medical conditions.

3. What should we tell callers about laboratory markers of immune status?

Both absolute and percentage CD4 counts and CD4-CD8 ratios are useful markers in the determination of HIV immune status, but they are each used for very specific purposes. In early infection and in asymptomatic infection, a ratio is more sensitive to corresponding changes that occur in CD4 and CD8 cell counts, whereas abnormally low CD4 cell counts are unusual. For example, an infectious mononucleosis-like syndrome has been described in association with acute HIV-1 infection and seroconversion. In this instance, CD4/CD8 ratios are usually low (because CD8 counts are elevated), whereas CD4 cell counts tend to be normal or low normal. In studies comparing persons with asymptomatic HIV infection to persons at risk for HIV infection, CD4/CD8 ratio is a much more sensitive indicator of HIV-1 infection than an absolute CD4 T-cell count.

Although the CD4/CD8 ratio is a more sensitive indicator of HIV-1 infection, absolute CD4 T-cell count is a more specific marker for severe immunodeficiency with clinical complications. Abnormally low CD4 T-cell counts are found in most AIDS patients at diagnosis; virtually all patients who survive long enough will eventually develop this abnormality. Low CD4 cell counts are unusual in asymptomatic infected people. Clinically, it is reasonable to use absolute (or percentage) CD4 T-cell determinations for monitoring HIV-1-infected patients, because these cells are the primary target of infection and their depletion reflects the severity of immunosuppression. CD4 cell counts are used as one criterion for arranging patients for entrance into clinical trials of experimental medicines, and CD4 cell counts will certainly be used for assessing response to therapy. In therapeutic trials, clinical outcome is the generally accepted measurement of therapeutic response; however, measurement of CD4 cell levels is an additional objective measure.

The diagnostic methods outlined in the December 18, 1992, MMWR (RR), "1993 revised classification system for HIV infection and expanded surveillance case definition for AIDS among adolescent and adults," are provided as guidance for the technique that should be used to definitively determine the AIDS indicator disease. More in-depth discussion is tantamount to several medical courses that would cover microbiology, laboratory, and laboratory diagnostic procedures and cannot be adequately discussed in this series of questions. Patients should be referred to their physicians if they have questions about the diagnostic measures which their physician has prescribed.

4. Besides referrals for counseling and support groups, how should we respond to concerns regarding the psychological well-being of asymptomatic people who are HIV+, but have a T4 cell count low enough to be diagnosed with AIDS?

Finding out that one is HIV infected or has AIDS (even before the expanded AIDS surveillance case definition) can be psychologically traumatic. Use previous experience to cope with issues arising from new cases which have been diagnosed due to a change in the surveillance case definition. We recommend referrals to counselors who are well trained and already equipped to handle the stress of learning of an AIDS diagnosis.

5. What benefits might there be for this kind of individual to be diagnosed?

The benefits of early intervention have been described extensively in the medical literature. Increasingly, attention is being focused on attempts to prevent further deterioration of the immune system in HIV-infected persons and prophylaxis against the more common opportunistic infections. Early intervention helps reduce further spread of the virus and may prevent or delay immunosuppression in HIV-infected persons. An integrated approach to the HIV- infected population would include treatment with available therapies, immunizations, Pneumocystis carinii pneumonia prophylaxis, nutrition, exercise, psychosocial support, evaluation for tuberculosis and "latent infections," and routine examinations and laboratory studies. Also, their health care and resource needs will be more accurately represented.

6. Does CDC recommend that people who are HIV+ obtain a T4 cell count? Yes. The Public Health Service recommends that CD4+ T- lymphocyte levels be monitored every 3-6 months in HIV- infected persons.

7. Are test sites encouraged to help people tested HIV+ obtain a T4 cell count?

Yes.

8. What qualifies a lab to do T4 cell counts?

In the MMWR Recommendations and Reports, dated May 8, 1992, CDC published "Guidelines for the performance of CD4+ T-cell determinations in persons with HIV infection." This document provides guidance to laboratories performing lymphocyte immunophenotyping assays. This report also provides information to laboratories on standard methods for performing the test, as well as guidelines for quality control and quality assurance. Criteria for a physician choosing a laboratory include a) laboratory accreditation, licensure, or certification by a recognized professional organization or governmental agency; b) laboratory participation in a recognized proficiency testing/performance evaluation program; and c) laboratory use of CDC or other published guidelines for flow cytometry.

9. How much do these tests cost and under what circumstances does insurance or Medicaid pay for them?

The average cost of a CD4 T-cell count assay ranges between $100-$150. Medicaid programs are handled by individual states, usually out of the state health department. Callers should be referred to their physician or state benefits coordinator for questions about Medicaid coverage.