CD4+ T-lymphocyte count/CD8+ T-lymphocyte count ratio: surrogate for HIV infection in infants?

Introduction: Early diagnosis and treatment is necessary to prevent HIV-infected infants progressing to AIDS. Antibody testing is not confirmatory before the age of 18 months and PCR not widely available in resource-poor settings. We studied the accuracy of CD4(+) T-lymphocyte count, CD4% and CD4/CD8 ratio as surrogate markers of infant HIV infection.

Methods: Two hundred and fifty-eight HIV-exposed Indian infants at a median age of 5 months (range 1-18) had DNA PCR and CD4, CD8 counts performed.

Results: Fifty five infants tested positive by HIV-1 DNA PCR whereas 203 were negative. Median CD4 count, CD4% and CD4/CD8 ratio were significantly lower in DNA PCR+ infants. Overall sensitivity and specificity of CD4/CD8 ratio <1.0 in predicting HIV was 91 and 92% with a negative predicted value (NPV) and positive predicted value (PPV) of 97 and 76%, respectively.

Conclusion: CD4/CD8 ratio <1.0 is a more sensitive surrogate marker of HIV infection in Indian infants than a CD4 count <1500 cells/µl or CD4% <25%.