Detection of human blood by immunoassay for applications in forensic analysis

The detection and confirmation of bloodstains as being human in origin is important in crime scene investigations. There are a number of blood detection methods currently available. The aim of this work was to develop an assay capable of detecting the presence of human blood from both liquid blood samples and dried bloodstains. A simple, direct competitive ELISA was developed utilising a polyclonal antibody against human IgG. Once optimised, the ELISA was found to be specific for human IgG, with no cross-reaction observed with pig, sheep, cow, goat, horse and rabbit IgG. The assay was also found to be sensitive, with a detection limit of 0.1 μg/mL. This compares favourably with leading blood detection methods. The assay was able to confirm the presence of human blood in blood mixtures, in stains on a variety of surfaces and also gave positive results with bloodstains that were up to 1 year old. The assay was simple to use, rapid and highly reproducible. The ELISA performance makes it suitable for development as a kit to rival currently used methods for the routine detection of human blood at crime scenes. Further applications of the anti-human IgG antibody are reported, including immunodot assays and a sandwich ELISA format.

The methods described here are simple, reliable assays for the identification of human blood and are presented as viable alternatives to existing techniques for blood detection.