Diagnostic power of peripheral blood phagocyte Fcg receptors expression in bacteraemia

Abstract number: 1134_04_184

Bernal J.A., Escobar M.A., Garcia-Egido A.A., la Hoz E., Aparicio J.M., Dominguez B., Romero A., Ruiz P., Rosety M., Rivera C., Gomez F.

Background:  

Early markers of bacteraemia are useful for prognosis and, in decision making for i.v. antibiotic therapy.

Objectives:  

To assess the diagnostic power of the surface expression of Fc receptors for IgG (FcgRs) for the prediction of bacteriemia in febrile patients.

Methods:  

We performed a 4 year prospective case-control study on 127 consecutive patients (pts) with an episode of bacteriemia as compared to 136 randomly selected concurrent febrile pts with negative blood cultures (control). Demographic and clinical data were collected by chart review and/or questioning their attending physicians. Plasma levels of C-reactive protein (CRP), TNFg, IL-1a, IL-6, IL-8 and IL-10 were determined. The surface expression of Fc receptors for IgG (FcgRs): FcgRI, FcgRII and FcgRIII on peripheral blood monocytes (M) and granulocytes (G) was assessed by flow cytometry. These studies were done concomitantly with blood cultures.

Results:  

Both groups were not different for age, sex, previous administration of immunosuppressants or antibiotics, clinical severity index or comorbid conditions. In univariate analysis, cases had significantly higher levels of CRP (p < 0.001), TNFg (p < 0.001), IL-1a (p < 0.001) and IL-6 (p < 0.01) than controls. The expression of FcgRIIA and FcgRIII by M and, that of FcgRI on G was significantly enhanced (p < 0.001) in bacteriemic patients as compared to culture-negative febrile pts; while the expression of FcgRIIB by either M or G was significantly decreased (p < 0.03). Setting a cut-off value = 25% of the mean fluorescence intensity over controls for FcgRs surface expression and, assuming a prevalence of bacteriemia of 5–10% among hospitalized patients undergoing blood cultures, results in a sensitivity, specificity, positive and, negative predictive values of: 77%, 97%, 74%, and 98%, respectively for M-FcgRIIA, 73%, 96%, 74% and 97%, respectively for M-FcgRIII, 58%, 93%, 49% and 95%, respectively for G-FcgRI and, 71%, 91%, 57% and 83%, respectively for G-FcgRIIB.

Conclusions:  

Our results suggest that the surface expression of Fc receptors for IgG on peripheral blood monocytes and granulocytes may help clinicians to rule out bacteraemia in febrile patients.