Common NICU Tests and Their Purpose

Complete Blood Count (CBC)
A CBC measures the levels of different types of blood cells. By determining if there are too many or not enough of each blood cell type, a CBC can help to detect a wide variety of illnesses or signs of infection.

Blood Chemistry Test (SMAC)
Basic blood chemistry tests measure the levels of certain electrolytes such as sodium and potassium in the blood, cells and body fluids. If the level of electrolytes in the body is too high or too low, the cells will not function properly, and the infant can become ill.

Blood Culture
A blood culture is a test to detect germs such as bacteria or fungi in the blood. One may be ordered when a baby has symptoms of an infection and the doctor suspects bacteria or fungi have spread into the blood. The culture can disclose what type of germ is causing the infection, which will determine how it is treated. Results are ready in a few days, but if the baby is severely ill, the doctor may start treatment before the results are complete.

Blood Gases
A small amount of blood is taken to analyze the levels of oxygen, carbon dioxide and other components. The results are used to determine the need and type of respiratory assistance your baby needs.

Blood Sugar
A drop of blood is taken to measure how much sugar is present in the blood.

As the body breaks down red blood cells, it produces a yellow substance called bilirubin. Bilirubin is then converted into a disposable form that can be passed out of the body in the stool. Jaundice of prematurity occurs frequently in premature babies since the body is less ready to excrete bilirubin effectively. Jaundice in babies is treated with phototherapy (bili lights) as described in the NICU Equipment section.

Congenital Heart Disease Screening
Beginning in January of 2012 a new screen (test) was added to the list of screens all babies receive before leaving the hospital. It is a screen to check infants for critical congenital heart disease or CCHD. 

Although CCHD is not a common disease, some babies with CCHD may look healthy and be sent home before their heart defect is detected. Therefore, pulse oximetry screening will be done prior to your baby leaving the hospital.

Pulse oximetry is a simple bedside test to determine the amount of oxygen in the baby’s blood and the baby’s pulse rate. Low levels of oxygen in the blood can be a sign of CCHD. The test is done using a machine called a pulse oximeter with sensors placed on an infant’s skin. The test is painless and takes only a few minutes. If the screen is “negative” (in-range results) it means that the baby’s test does not show signs of CCHD. This type of screening does not detect all CCHDs, so it is possible to still have a critical or other heart defect with a negative screen. If the results are “positive” (out of range result), it means that the baby’s test results showed low levels of oxygen in the blood. This can be a sign of CCHD but does not always mean that the baby has a CCHD. It just means that more testing is needed.

A physical exam is also done by the baby’s NICU physician to determine if CCHD is present. If the pulse oximeter test is positive, he/she will order further testing.

Please talk to your baby’s physician if you have additional questions regarding CCHD, and read the handout in the front of this notebook. (Adapted from

Echocardiogram (ECHO)
An echocardiogram, or "echo," is an ultrasound picture of the heart structures (chambers, walls and valves). It records the motion of the blood through the heart and can measure the direction and speed of blood flow within the heart structures.

Electroencephalogram (EEG)
An electroencephalogram (EEG) is a test used to detect abnormalities related to electrical activity of the brain. This procedure records brain activity from the needle electrodes just under the skin. Normal electrical activity in the brain makes a recognizable pattern. Through an EEG, doctors can look for abnormal patterns that indicate seizures and other problems.

Eye Exam
Some infants are at risk for vision problems due to their prematurity. If your baby weighs less than 1500 grams (3lbs. 5oz) and/or was less than 30 weeks gestational age at birth, the infant will need to have eye exams to look for signs of Retinopathy of Prematurity (ROP). The eye doctor, ophthalmologist, will examine the retina (the lining of the back of the eye) and blood vessels in the back of the eye. These examinations are usually every two weeks until the blood vessel growth in the eye is completed. After discharge, your baby will continue to have these eye exams as an outpatient in the ophthalmologist’s office. Ask your baby’s physician for more information on ROP.

Head Ultrasound
A head ultrasound uses sound waves to form a picture of the internal structures of the brain. A head ultrasound is done to rule out neurological complications of prematurity, such as bleeding in the brain (intraventricular hemorrhage or IVH) or injury to the white matter of the brain surrounding the ventricles (periventricular leukomalacia or PVL). A "normal" ultrasound does not guarantee that your baby’s brain is developing normally, but it is reassuring.

Hearing Screen
The American Academy of Pediatrics (AAP) recommends that all babies have a hearing screen done before discharge from the hospital in order to identify hearing loss in newborns as early as possible. It is important to pick up hearing deficits early so that they can be treated. Hearing screens take 5–10 minutes and are painless. The screen involves placing electrodes on the infant’s head and body to monitor responses and uses cuplets placed over the ear to transmit sound. Most babies
pass the hearing screening, indicating that hearing is adequate for normal speech and language development. If your baby does not pass the screening, your primary care provider will set up a diagnostic hearing test appointment for you to determine the hearing status of your baby. If your family has a history of hearing loss, please let your baby’s physician know.

Blood is collected usually by heelstick from the baby’s heel. Hemoglobin is a protein in the red blood cells that carries oxygen. Hemoglobins are checked weekly on all babies in NICU.

A stool (feces) sample can provide doctors with valuable information about what's going on when your child has a problem in the stomach, intestines, rectum or other part of the gastrointestinal (GI) system. One of the most common reasons to collect a sample is to determine if there's blood in the stool. To test the stool for the presence of blood, a noninvasive test called the fecal occult blood test is performed. The test detects hidden (occult) blood in the stool—blood that cannot be seen by the naked eye.

Newborn Screen
The Newborn Screen is a blood test that identifies babies who are at risk for serious disorders that are treatable. State law requires that all babies have a routine Newborn Screening. The initial testing is done by collecting a few drops of blood in the first week of life.

Specific Gravity & Combistix
Urine is collected by placing a piece of cotton into the infant’s diaper. Once a urine sample is collected, a nurse will place several drops of urine onto a specially treated chemical strip (combistix). Patches on the dipstick will change color to indicate the presence of such things as white blood cells, protein or glucose. The results of a urine dipstick test may point to a diagnosis of urinary tract infection (UTI) or a urinary tract injury. If test results are abnormal, other tests will be needed before a definite diagnosis can be made.

X-rays can help doctors find a variety of conditions. A portable X-ray machine takes a picture of the area the doctor is concerned about and produces an image of internal body parts. X-rays are taken at intervals indicated by your baby’s illness and progress.