No preparation is required for newborn testing, which usually takes place in the hospital between 24 hours and seven days after a child is born. Parents should have their children follow any preparatory directions provided by the physician or other healthcare professional.

Lab tests may be performed differently depending on the nature of the tests. During a newborn test, a nurse or other healthcare professional will prick the baby’s heel to obtain a small amount of blood. This will be sent to a laboratory for analysis.

The technique for drawing blood depends on how much blood is needed. If the test requires only a drop or two of blood, then a simple prick of the finger or earlobe can provide enough blood for testing. A sterile, sharp lancet is used to prick the skin. The technician will then gently squeeze the puncture area to produce drops of blood that are collected in tiny glass tubes. Light pressure and sterile gauze are then applied to the puncture site to stop the bleeding. A bandage may be applied.

If a substantial amount of blood is needed, it is usually drawn from a vein in a process called venipuncture. During venipuncture, a needle is inserted into a vein – usually at the inside of the elbow or on the back of the hand. The area around the puncture site is cleaned with rubbing alcohol and a wide elastic band or piece of latex tubing may be placed around the upper arm to slightly increase pressure in the vein. One end of a sterile double-ended needle that has been attached to an open-ended syringe (which contains an empty test tube) is inserted into the vein. Because the test tube contains a partial vacuum, blood flows directly from the vein through the double-ended needle and into the test tube.

After the necessary amount of blood is drawn, the needle is withdrawn and a small cotton ball or pad is applied with light pressure over the puncture site. After several minutes, the cotton will be discarded or replaced, and a small bandage will be placed on the puncture wound. The entire process takes less than 10 minutes.

Collecting a urine sample usually takes just minutes to complete. Performed in a physician’s office, the urine test will require a 1- to 2-ounce (30- to 60-milliliter) sample to be collected in a cup. The urine sample should not be brought from home because the urine needs to be as fresh as possible. The child will provide the sample by urinating into a receptacle used for this purpose.

During throat cultures, children are asked to open their mouths wide while a long cotton swab is inserted and the back of the throat is wiped.

Samples for stool tests are often collected in the home. Parents will likely need to help their young children with this process, which is explained in detail by a physician.

During a spinal tap, infants and small children lie on their sides curled up in a position that resembles the letter “C,” with their knees under their chin. Teens lie on their sides with their knees drawn up to their chest and chin resting on their chest.  A local anesthetic is used to numb the lower back, and a small, hollow needle is inserted near the waist to draw out a sample of cerebrospinal fluid (CSF).