Blood donation and will screen for antibodies to less common antigens. More testing, including a crossmatch, is usually done before a transfusion. Type O negative is often cited as the "universal donor" but this only refers to red cell and whole blood transfusions. For plasma and platelet transfusions the system is reversed: AB positive is the universal platelet donor type while both AB positive and AB negative are universal plasma donor types. Most blood is tested for diseases, including some STDs. The tests used are high-sensitivity screening tests and no actual diagnosis is made. Some of the test results are later found
ABO blood group system A and B antigens, but contains anti-A and anti-B. The following year, his students Adriano Sturli and Alfred von Decastello discovered the fourth type (but not naming it, and simply referred to it as "no particular type”). In 1910, Ludwik Hirszfeld and Emil Freiherr von Dungern introduced the term 0 (null) for the group Landsteiner designated as C, and AB for the type discovered by Sturli and von Decastello. They were also the first to explain the genetic inheritance of the blood groups.) Czech serologist Jan Janský independently introduced blood type classification in 1907 in a local journal. He used