During collection of capillary blood from an infant or a young child, stress can play a negative effect on the test results. Excessive crying in infants can increase the white blood cell (WBC) counts. It takes at least 60 minutes for the WBC levels to return to normal. If an infant has undergone a painful procedure, such as a circumcision, care must be taken to allow the proper amount of time to pass before collecting capillary blood.
It has also been determined that stress can decrease serum iron levels and increase adrenocorticotropic hormone (ACTH), catecholamine, and cortisol levels.