CD4 Cell Count Preferred over CD4 Cell Percentage for Monitoring HIV Disease Progression in People with Cirrhosis

By Liz Highleyman

CD4 cell count is typically used to monitor the progression of immune suppression in people with HIV and to indicate when to begin antiretroviral treatment, but CD4 cell percentage is preferred in some circumstances (e.g., for infants). While the absolute CD4 count shows the number of cells in a small quantity of blood, the CD4 percentage tells how many of the total lymphocytes are CD4 cells.

Recent research showed that HIV negative patients with liver cirrhosis had low CD4 cell counts, but normal CD4 cell percentages. This suggested that CD4 cell percentage might be a more accurate marker of disease progression than absolute CD4 cell count in cirrhotic patients with HIV.

Italian researchers conducted a study to compare the relative prognostic value of absolute CD4 cell count and CD4 percentage for predicting AIDS-defining events in HIV positive patients with cirrhosis. Results were reported at the 4th International AIDS Society Conference on HIV Pathogenesis, Treatment, and Prevention in Sydney, Australia (July 22-25, 2007), and also published in the September 1, 2007 issue of Clinical Infectious Diseases.

The study included about 6000 HIV positive participants in the Italian Cohort of Antiretroviral-Naive Patients (ICoNA). Most (70%) were men and the median age was 35 years. The median CD4 cell count at enrollment was 427 cells/mm3 (range 1-1361) and the median CD4 percentage was 23% (range 1%-81%). In this cohort, 38% were coinfected with hepatitis C virus (HCV) and 5% tested positive for hepatitis B surface antigen. About 4% had an AIDS-defining illness at enrollment and about 3% had cirrhosis (in addition, about 1% more progressed to cirrhosis during follow-up).

Three groups were identified:

• Group 1: subjects with histological and/or clinical evidence of cirrhosis;

• Group 2: HCV and/or HBV coinfected subjects without cirrhosis;

• Group 3: subjects without liver disease (negative for HCV and HBV, ALT < 40 IU/L).

Results

• 402 new AIDS-defining events were reported during 25,693 person-years of follow-up, for an incidence rate of 1.6 per 100 person-years.

• In patients with cirrhosis, higher CD4 cell counts -- but not higher CD4 percentages -- were associated with a lower risk of progression to AIDS (relative risk 0.58 per additional 100 cells/mm3; 0.61 per additional 10% higher).

• In Group 2 and Group 3, both absolute CD4 cell count and CD4 percentage were associated with a higher risk of AIDS (Group 2 RR 0.75 per 100 cells/mm3, 0.54 per 10%; Group 3 RR 0.52 per 100 cells/mm3, 0.61 per 10%).

• After controlling for CD4 cell values, patients with cirrhosis were significantly more likely to progress to AIDS than those without.

Conclusion

"Our data indicate that the absolute number of CD4 cells is a better predictor of AIDS-[defining] events than CD4 percentage in HIV-infected patients with cirrhosis, but not in those with HBV and/or HCV coinfection or without liver disease," the researchers concluded.

As such, they advised, "[A]bsolute CD4 cell count should be used to guide therapy decisions for all HIV-infected patients."

San Paolo Hospital, University of Milan, Italy; National Institute of Infectious Diseases, L. Spallanzani, IRCCS, Rome, Italy; University Cattolica del Sacro Cuore, Rome, Italy; San Martino Hospital, Genova, Italy; Macerata Hospital, Macerata, Italy; University of Brescia, Italy; Royal Free and University College Medical School, London, UK.

08/21/07

References

M Bongiovanni, A Gori, A Cozzi Lepri, and others (for the Italian Cohort of Antiretroviral-Naive Patients Study Group). Is the CD4 Cell Percentage a Better Marker of Immunosuppression than the Absolute CD4 Cell Count in HIV-Infected Patients with Cirrhosis? Clinical Infectious Diseases 45(5): 650-653. September 1, 2007.

M Bongiovanni, A Gori, A Cozzi Lepri, and others. Is CD4 percentage a better marker of immune-suppression than CD4 absolute count in HIV-infected subjects with cirrhosis? 4th International AIDS Society Conference on HIV Pathogenesis, Treatment, and Prevention. Sydney, Australia, July 22-25, 2007. Abstract MOPE063.

* B H McGovern, Y Golan, M Lopez, and others. The Impact of Cirrhosis on CD4+ T Cell Counts in HIV-Seronegative Patients. Clinical Infectious Diseases 44(3): 431-437. February 1, 2007.