What Does A Heel Stick Test For?

The heel stick test for newborns is a quick prick on the heel of the baby using a lancet. This is the least traumatic way to draw blood from infants for routine testing.

Heel stick is the most common and minimally invasive method to draw capillary blood from an infant for medical testing. Capillaries are tiny blood vessels which carry blood to the tissues and connect arteries to the veins. A sharp device known as a lancet is used to prick the baby’s heel to obtain blood samples.

Heel stick blood samples are used for tests such as:

• Complete blood counts
• Liver function tests
• Toxicologic tests
• Bedside glucose monitoring
• Blood gas analysis
• Newborn screening tests

Newborn screening is one of the primary reasons for a heel stick. Newborn screening is a state-mandated program in the US, though efforts are underway to develop a national newborn screening program.

A screening heel stick is usually performed within 48 hours after a child’s birth or as soon as possible. Early detection of any genetic disorders can help with effective treatment or even prevention of disease in certain cases. More than 95% of American newborn babies undergo screening for up to 50 genetic disorders which include:

• Phenylketonuria: A metabolic disorder
• Sickle cell disease: Red blood cell disorder
• Hypothyroidism: Underactive thyroid
• Cystic fibrosis: A disease that affects lungs and the digestive system

The heel stick method can be used until a baby is four to seven months old, when babies are normally able to place their toes in their mouth. Heel sticks must not be done once the babies start bearing any amount of weight on their feet.

The heel is a viable source of blood whenever capillary blood is acceptable as a sample for testing. A heel stick is a simple and safe way to draw blood in newborns in situations that include the following:

• Only a small blood sample is required for testing.
• Multiple and frequent blood tests are required.
• Other sources, like a venous or umbilical catheter, are not already available.

A heel stick is not performed in the following situations:

• If the baby’s sampling area in the heel has any
  • Injury
  • Anomaly
  • Infection
  • Edema
• If blood volume required for testing is relatively larger
• Certain types of blood tests such as
  • Coagulation tests
  • Blood cultures
  • Chromosomal analyses
  • Immunoglobulins and titers

The safest sites for an infant heel puncture are the edges of the heel on the inside (medial) and outside (lateral). The curve in the back of the heel should not be used for a heel stick in order to prevent injury to the calcaneus bone, which is close to the skin in the posterior heel. Previous puncture sites must also be avoided.

A pediatrician or a nurse trained in pediatric care performs the heel stick in a newborn infant.

Preparation

Anesthesia is not required but the doctor makes the baby comfortable with:

• Swaddling
• Reduced ambient light and noise
• Oral sucrose administered with a filler or a pacifier dipped in sugar solution
• The doctor may apply a heel warmer to warm the heel for five minutes before the procedure.

Procedure

The doctor

• Cleans the heel stick site with an antiseptic solution
• Holds the heel between their thumb and forefinger
• Applies light pressure on the heel
• Places the lancet on the appropriate spot and activates it
• Applies mild pressure to squeeze out a blood drop
• Wipes away the first drop as it can contain some of the antiseptic solution and interfere with the test results
• Collects the blood in a collection tube
• Blots blood drops in filter paper used for testing
• Applies pressure to stop bleeding
• Places a bandage over the heel stick site

Complications can mostly be avoided by employing proper care during a heel stick. Improper heel stick technique can cause damage to the calcaneus bone and soft tissue. Other potential complications include:

• Pain
• Infection leading to
  • Cellulitis
  • Abscess
  • Osteomyelitis
• Scarring
• An incision that is too deep
• Inaccurate results