A direct lead technique for histochemical demonstration of leucocyte alkaline phosphatase activity in blood smears

A histochemical technique for demonstrating leucocyte alkaline phosphatase activity (LAP), based on direct precipitation of lead phosphate at pH 9.5, is described. The effect of fixative, temperature and stability of the medium on the activity of the enzyme and stability of the colour reaction was thoroughly studied. Peripheral blood smears obtained from both normal humans and pathological cases were studied and the results were compared with these obtained by the azo-dye method.