Blood or Serum Collected on Filter Paper for Detection of Antibodies to Bovine Herpesvirus Type 1 (BoHV-1)

Background: The method of collection as well as the packaging conditions in which samples are submitted to laboratories play a critical role on the acquisition of reliable results on diagnostic tests. Alternative methods however have been proposed, as the adsorption of blood or serum in filter paper. In this work, it was evaluated the viability of using serum or whole blood samples from bovines collected in filter paper for serological testing against bovine herpesvirus type 1 (BoHV-1). Materials, Methods & Results: One hundred and seven whole blood and serum samples were collected by standard methods. Serum neutralization test was used as a golden standard method for evaluation of the serum samples. The same samples of both whole blood and sera were also adsorbed on filter paper strips for further comparisons. Optimal conditions for serum and blood elution from filter paper were determined. Adsorbed samples on filter paper disks were eluted in PBS and subsequently diluted further with PBS 5% skimmed milk. The eluates were tested for antibodies to BoHV-1 in an indirect ELISA (iELISA) and matched with the results obtained by serum neutralization of standard serum samples. Comparison between results obtained by serum neutralization of standard serum samples and the ones from the iELISA of serum eluted from paper disks resulted in sensitivity, specificity, positive and negative predictive values of 95, 94, 80, 99%, respectively, and a correlation coefficient (kappa) of 0.83. Comparison between the results of serum neutralization of standard serum samples and the ones from the iELISA of blood eluted from paper disks resulted in sensitivity, specificity, positive and negative predictive values of 91, 97, 87, 98%, respectively, and a correlation coefficient (kappa) of 0.86. Standard serum samples were also tested in the iELISA and the results compared with those of iELISA from samples eluted from filter paper. Comparison of the results from iELISA between serum samples and serum eluted from filter paper resulted in sensitivity, specificity, positive and negative predictive values of 91, 81, 69, 95%, respectively, and a correlation coefficient (kappa) of 0.66. The comparison of iELISA results between standard serum and blood samples eluted from filter paper resulted, in sensitivity, specificity, positive and negative predictive values of 78, 92, 82, 89%, respectively, and a correlation coefficient (kappa) of 0.70. Fifty samples collected on filter paper were retested eight months later in order to determine whether those would retain its viability; both sensitivity and specificity remained unaltered. Discussion: Sampling on filter paper has been successfully described for antibody detection in a number of diseases such as Aujeszky's disease virus and Newcastle disease virus. In this work, it has been demonstrated that both blood and sera collected in filter paper can be used for submission of samples aiming detection of antibodies to BoHV-1 in an iELISA, without significant loss of sensitivity and specificity. Submission of samples on filter paper is a practical and economical alternative as no special conditions are required for storaging and transporting. This method also enables the collection of samples from distant places assuring its quality for serological tests.