Laboratory tests inform us about the ongoing processes in the human body and its changes - both physiological and pathological. The disease is actually upset the balance, transformation in pathological physiological processes, and these changes are immediately reflected in the altered biochemical reaction.
Changes in laboratory values may occur in some cases even before the disease the patient exhibits; certain parameters reflect pathological changes within a few minutes (e.g. myoglobin in acute myocardial infarction).