Effects of blood contamination of cerebrospinal fluid on western blot analysis for detection of antibodies against Sarcocystis neurona and on albumin quotient and immunoglobulin G index in horses.

摘要

Blood with various degrees of immunoreactivity against S. neurona was collected from 12 healthy horses and cerebrospinal fluid (CSF) without immunoreactivity against S. neurona was collected from 4 recently killed horses. Blood was serially dilutedwith pooled non-immunoreactive CSF so that final dilutions corresponded to 10-3 to 100μl of blood/ml CSF, and western blotting was performed on contaminated CSF samples. In CSF samples contaminated with 10μl of blood/ml, albumin quotient (AQ) remainedwithin reference range. Volume of blood required to increase IgG index varied among blood samples and was primarily influenced by serum IgG concentrations. Erythrocyte count in contaminated samples was correlated with volume of blood added, but not withdegree of immunoreactivity detected in contaminated CSF samples. It is concluded that contamination of CSF with blood during collection may introduce serum antibodies against S. neurona at concentrations sufficient for detection by western blotting thusyielding false-positive results. When blood is moderately or strongly immunoreactive, the amount of contaminating albumin may be small enough as to not increase AQ above reference range. In these cases, AQ and IgG index should be interpreted with caution.