Final answer:
A left shift is an increase in neutrophil precursors, such as band cells and metamyelocytes, in peripheral blood.
Step-by-step explanation:
A left shift refers to an increase in neutrophil precursors in peripheral blood. This includes immature neutrophils such as band cells and metamyelocytes. Therefore, the statement 'A left shift is an increase in neutrophil precursors in peripheral blood' is true.