To perform specific HLA genotyping, extraction of DNA from the cells is required. DNA extraction can be performed by lysing leukocytes or other host cells that contain DNA. Cellular debris and non-DNA macromolecules (proteins, carbohydrates, lipids, and RNA) must be removed by washing steps. Methods to aggregate DNA to remove debris typically include salt precipitation and/or the use of purifying columns. Automated techniques using salting-out technique or metallic beads also exist.
DNA may be extracted manually from the buffy coat of centrifugated whole blood. DNA may be extracted from other body sites like bone marrow, lymph nodes, splenic tissue, buccal cells, and hair follicles. Laboratories commonly use EDTA or ACD1 yellow-topped tubes.
