A simple dot enzyme-linked immunosorbent assay for ABO blood typing of biological fluid and stains: effects of heating samples

A simple dot enzyme-linked immunosorbent assay (Dot-ELISA) using commercially available monoclonal anti-A and anti-B antibodies and biotinylated anti-H lectin was developed for ABO blood typing of biological fluid and stains. Its application to forensic practice was examined with 117 saliva samples and their stains, and practical case samples of 8 seminal, 6 vaginal and 45 aged salivary stains. In the simple Dot-ELISA, a new step to heat biological samples was introduced in the system in order to block unfavorable non-specific reactions of the samples with secondary enzyme conjugate. The simple Dot-ELISA could determine accurately the ABO blood type of a small amount of secretor's and non-secretor's salivary samples. In practical tests of seminal, vaginal and salivary stains, all results were confirmed to be identical to those determined by the conventional absorption-inhibition test and the absorption-elution test. The simple Dot-ELISA is considered to be accurate, rapid, simple, sensitive and easy to perform in routine forensic practice. It is also a unique and helpful method to determine the ABO blood types of various biological samples.