Influenza-specific hemaggluitination inhibition (HAI) antibody titer, an signal of immunity to influenza, is definitely often used to measure exposure to influenza in surveillance and immunogenicity studies. degree of agreement (80.5%C98.8%) and correlation (r?=?0.796C0.964) in the serum and matched plasma titer ideals although plasma titers were generally lower than corresponding serum titers. Calculated seropositive (HAI 40) rates were higher using serum titers than with plasma titers, but seroconversion rates were unaffected by sample type. Stronger agreement and decreased variability in titers were seen between serum and citrated plasma than between serum and heparinized plasma. Overall, these data suggest that serum or plasma can be used in serodiagnostic HAI assays, but seropositive rates may be underestimated using plasma HAI titers. The type of anticoagulant present in plasma may impact HAI titer ideals and warrants further investigation. Intro The influenza hemagglutination-inhibition (HAI) assay 1st explained in the 1940’s (Hirst 1942, Salk 1944) is the traditional method for measuring immune reactions to influenza disease hemagglutinin (HA), the principal antigen relevant to safety. The HAI assay is used extensively for evaluation of influenza vaccine effectiveness and in epidemiological studies of influenza disease infection. Mechanistically, the assay capitalizes on the fact that HA glycoproteins on the surface of influenza virions bind and agglutinate erythrocytes. The attachment of serum antibodies to specific epitopes within the HA glycoprotein interferes with disease binding to receptors within the erythrocytes, inhibiting agglutination. Historically, serum has been used in the overall performance of TBC-11251 HAI , , , . However, in individual subject matter clinical tests more and more, plasma is normally a chosen and even more gathered specimen type in comparison to serum  often, , . That is due partly towards the near universality of plasma as the specimen of preference for calculating many analytes in individual examples coupled with bloodstream volume constraints enforced on human subject matter research. Hence, it is appealing to review HAI activity amounts in plasma and serum. This is also true in retrospective epidemiological research wanting to chronicle a recently emergent influenza stress within an affected area when previously gathered plasma may be the just sample type designed for testing. In such instances the validity of plasma HAI antibody titers should come into issue. We have recently collected high-titered plasma devices from influenza convalescent individuals and vaccine recipients for use in a randomized, multicenter study to explore the effectiveness of convalescent plasma therapy as an alternate treatment modality for severe influenza disease. In order to determine and/or confirm the HAI titers of plasma units to be used in immunotherapy, serum from unit donors were tested. However, it may be more practical to directly test the plasma units on the hospital blood bank shelves to determine acceptability prior Rabbit Polyclonal to 14-3-3 eta. to infusion into patients. Anticoagulants present in plasma are known to interfere with antibody-antigen reactions TBC-11251 and may inhibit the activity of some enzyme reagents , . For these reasons plasma has traditionally not TBC-11251 been considered the specimen of choice for assays that either measure antibodies or require enzyme reagents. In the case of influenza HAI, anticoagulants may interfere with binding of antibodies to the HA molecule of the virus, or hinder enzyme activity during the elimination of non-specific inhibitors of agglutination in test samples. Nonetheless, there are published reports of HAI titers obtained from plasma samples , . Other investigators have reported HAI titer values derived from a combination of serum and plasma samples , though unfortunately a detailed comparison of the serum and plasma HAI titers was not presented. To date, no detailed account elucidating the HAI titer difference between temporally matched serum and plasma TBC-11251 has been reported. Additionally, the impact of TBC-11251 anticoagulant selection on plasma HAI results has not been examined. The purpose of this study was to evaluate the correlation and agreement of HAI antibody titers of temporally matched serum and plasma samples and to ascertain if plasma can be used in place of serum in standard influenza HAI testing. We assessed the effect of anticoagulants in HAI assay variability also. Five influenza disease strains and two specific anticoagulated plasma were found in this scholarly research to judge potential differences in HAI.