Could CD64 expression be used as a predictor of positive culture results in children with febrile neutropenia?

BACKGROUND Early recognition of infectious processes in neutropenic patients is hampered by the fact that these processes may have dissimilar and non-specific clinical presentations. CD64 is a neutrophil surface marker that is not expressed in non-sensitized neutrophils. When the neutrophil is exposed to tumor necrosis factor-alpha it is activated and is measured via the CD64 index. METHODS This paper evaluated the relationship between the index value of CD64 on the first day of febrile neutropenia and a positive blood culture. The correlations with white blood count, C-reactive protein and erythrocyte sedimentation rate were also evaluated. This case-control, prospective, diagnostic study included 64 episodes of neutropenia. Case group (n=14) comprised positive blood cultures, and the control group (n=50), negative blood cultures. RESULTS The median rates of CD64 were 2.1 (σ±3.9) in the case group and 1.76 (σ±5.02) in the control group. There was no correlation between the value of the CD64 index and blood cultures. The CD64 index was also not correlated with C-reactive protein positivity. Furthermore, the CD64 index was not able to predict blood culture positivity. The sensitivity was 64.3%, the specificity was 42%, the positive predictive value was 23.7% and the negative predictive value was 80%. For C-reactive protein, the sensitivity, specificity, positive predictive value, and negative predictive value were 71.4%, 32%, 22.7%, and 80%, respectively. CONCLUSION The CD64 index is not suitable for predicting the positivity of blood cultures in this specific population of patients with febrile neutropenia.