Predicting CD4 counts in HIV-infected Brazilian individuals: a model based on the World Health Organization staging system.

CD4 cell counts are one of the best available surrogate markers for disease progression; they are widely used laboratory parameters in clinical trials and commonly used indicators for the introduction of primary prophylaxis and antiretroviral therapy. However, measurement is too expensive to be done in most developing countries. The objective of this study was to derive a model for prediction of CD4 counts < 200 cells/mm3 based on the proposed World Health Organization (WHO) staging system for HIV infection and widely available laboratory parameters. One hundred and six consecutive patients enrolled in a prospective cohort study who were not taking anti-HIV drugs or prophylaxis for opportunistic infections were included. Blood tests were performed within 72 h of the outpatient visit. Lymphocyte phenotyping was done by flow cytometry. Two models based on the WHO staging system, hematocrit and total lymphocyte counts, were developed. The two models had sensitivity > 90% and specificity > 83%. These results indicate that the combined use of simple clinical and laboratory parameters can predict CD4 counts < 200 cells/mm3 with high sensitivity and specificity. Similar studies should be conducted in other countries. Should our findings be confirmed, intervention strategies based on this model of potential universal applicability should be devised and validated.