Highlights • Typhim Vi response have been proposed as a new strategy for the assessment of specific polysaccharide antibody response in SID due to HM. • Different biostatistical methodologies may stablish the best cut-off value to discriminate Typhim Vi response. • Typhim Vi IgG responses may better discriminate primary Ab responses showing relevant clinical correlate. Assessment of specific antibody (Ab) production to polysaccharide antigens is clinically relevant, identifying patients at risk for infection by encapsulated bacteria and thus enabling a more rigorous selection of patients that can benefit of immunoglobulin replacement therapy. Classically, the gold-standard test is the measurement of antibody production to pure polysaccharide pneumococcal (PPV) immunization. Several factors, including introduction of conjugate vaccination schedule, serotyping analysis, high baseline Ab levels, have hindered the evaluation of polysaccharide antigens. This is even more difficult in secondary immunodeficiencies (SID), where patients can show secondary responses despite lack of primary antibody responses and present with recurrent or severe infections. Assessment of specific Ab production to pure S almonella typhi Vi polysaccharide (TV) immunization has been proposed as a complementary test to PPV, given its low seroprevalence. To set the optimal cut-off value for PPV and TV response in SID, we tested different biostatistical methodologies, including ROC analysis, Youden index, Union index and Closest-topleft in a cohort of 42 SID patients and 24 healthy controls. The statistically chosen cut-offs value pre-post TV Ab ratio was ≥5, (sensitivity of 90%, specificity of 100%) and a postvaccination TV concentration of 28.5 U/mL (sensitivity of 90%, specificity of 95%), showing relevant clinical correlate. Graphical Abstract Image, graphical abstract
【저자키워드】 Hematological malignancies, ROC Curve, primary responses, Typhim Vi, Specific polysaccharide ab response, Pneumo 23, secondary responses, Union index, cut-off value, Youden index,