Screening Feline Blood Donors for Bartonella henselae Infection: Comparison between Indirect Immunofluorescent Antibody Test (IFAT) and Polymerase Chain Reaction (PCR) Results

In order to minimize pathogen transmission, all blood do- nors should be appropriately screened for infectious agents. Screening for Bartonella spp. infection in feline blood donors is a recommended practice in veterinary blood banks across the world. The aim of this study was to compare results of an indirect immunofluorescence antibody test (IFAT) in identifying Bartonella henselae antibodies with the results of PCR amplification of Bartonella spp. DNA to establish the best IFAT cut off to identify non-bacteremic cats. A secondary aim of this study was to evaluate demographic and clinicopathologic factors that may be associated with Bartonella henselae infection status. From a population of stray cats in Milan city, 82 serum samples were evaluated by IFAT for Bartonella henselae antibodies and PCR was performed on 90 whole blood samples for amplification of Bartonella spp. DNA. A total of 14/82 (17.1%) samples were seropositive with an IFAT titer ≥1:64 (cut-off for infection). Bartonella spp. DNA was identified in 11/90 (12.2%) samples by PCR. Overall 20/90 (22.2%) infected cats were identified by either IFAT ≥1:64 and/or PCR-positive results. Hyperbetaglobulinemia (P=0.02) and originating from zone 2 of Milan city (P=0.03) were statistically associated with positive Bartonella infection status. The overall IFAT sensitivity was 50.0%, specificity 87.5%, positive predictive value 35.7% and negative predictive value was 92.65%. The ROC analysis showed that the area under the curve was 0.747 (P=0.0032) and that an IFAT cut off<1:32 had the highest sensitivity in identifying Bartonella PCR-negative cats. When feline blood donors undergo serological screening for Bartonella henselae infection an IFAT cut off <1:32 has the highest sensitivity for identifying non-bacteremic cats. However some serologically negative cats could be bacteremic and therefore screening of a feline blood donor using a combination of IFAT and PCR is recommended. Protein electrophoresis should be performed in all potential donor cats.