The manual hexadimethrine bromide (Polybrene) test. Effects of serum proteins and practical applications.

Serum proteins affect the performance of the manual hexadimethrine bromide (Polybrene) test. Red cells suspended in the low-ionic medium adhere to the surface of test tubes when centrifuged. This adherence is prevented by serum components apoprotein B, fibronectin, von Willebrand factor, or serum diluted less than 75-fold, but not by serum albumin or immunoglobulin fractions. A high concentration of serum reduces the sensitivity of the test and destabilizes antibody-dependent aggregation. Disaggregation time (DT), defined as the time required for antibody-dependent aggregates to disperse, was used as an indicator of agglutination stability. DT was often shortened when antibodies were in native serums, but could be prolonged if serums were diluted with 0.85 percent saline. Other factors that influenced DT included antibody concentration, temperature, specificity, and sources of antibodies within specificities. When antibodies were present in a mixture, they produced various DTs related to individual specificities. Determination of these differences allowed the successful identification of multiple antibodies. The procedure, called differential disaggregation time, was also used for typing red cells coated by autoantibodies. Additional modifications improved the performance of the antiglobulin phase.