Purpose of the test

The purpose of screening newborn babies is to detect selected genetic disorders at a very early stage of life before devastating illness and damage occurs. The goal is to provide early treatment that would improve the long term prognosis for these children.

Basics the nurse needs to know

Newborn screening tests began in the 1960s with the development of the Guthrie test to detect the disorder of phenylketonuria (PKU). Since that time, blood tests for numerous other genetic disorders have been developed. Importantly, new laboratory equipment [Tandem Mass Spectrometry (MS/MS)] has been invented to analyze the large numbers of screening specimens in newborns and multiple tests for each baby. Today, there are more than 30 tests available to screen the newborn, using only one blood specimen per baby.

Newborn screening detects disorders that are present at birth but the disorders demonstrate no immediate symptoms. If undetected and untreated, these disorders will result in significant mental retardation, developmental disability, or death. The permanent damage usually occurs within months of birth. One of the selection criteria of a newborn screening test is that the disorder must have effective treatment that can limit the symptoms of illness and prevent disability before it occurs (Gilbert-Barnes, Kapur, Oligny & Siebert, 2007).

In the United States, the decision for mandatory screening and the choices of specific screening tests are controlled by the individual states and their respective legislators. Generally, the individual state health departments and their maternal and child health programs are responsible for implementation of the laws regarding screening in their states. The screening programs and the subsequent treatment for the children with the genetic disorder are funded under title V of the Social Security Act.

Testing for PKU and hypothyroidism are mandatory in all states of this country, but among all the states there is considerable variation regarding other tests that are included in mandatory newborn screening. The diseases that are more commonly assessed by newborn screening are presented in Box 7. In general, the tests include those for cystic fibrosis, selected endocrine tests, selected hemoglobin disorders, and selected disorders of metabolism. In some states, a mandatory screening test for hearing also is done, but since the method is not done by a laboratory test, the topic is beyond the scope of this book.

All screening tests have a somewhat high percentage of false-positive results. A false positive means that the test demonstrated a positive result, but the infant does not have the disease. False-negative results may also occur. False negative means that the infant has the disease, but the laboratory screening test was negative. When there is medical doubt about the screening test result, a repeat screening test may be done in 7 days. Positive screening tests are always followed up with more specific testing to confirm or exclude the final diagnosis.

How the test is done

Capillary puncture of the heel is done to obtain a sample of the newborn’s blood. The blood is collected on filter paper and dried before placing the paper in an envelope.

Significance of the test results

Interfering factors

Purpose of the test

A nuclear scan is used to assess the physiologic function and assist in the localization of abnormality in a designated organ or tissue.

Basics the nurse needs to know

In most radiologic procedures, the source of the radiation is in a machine that emits radio waves aimed to pass through the patient from the external source. In the nuclear scan, the process is different, because the radiation source is within the patient. Once in the patient’s body, the radionuclide is taken up, concentrated, and distributed in the targeted organ or tissue. For a short time, it emits gamma rays in the pattern and concentration that correspond to the physiologic uptake of that tissue. A gamma camera or scintillation scanner detects and records the emission of the gamma rays. The data are converted into a visual image by the computer and its special software.

In a nuclear scan, the source of the radiation is a radionuclide, a radioactive isotope that has a short half-life. This means that the isotope emits gamma rays or photons for a few hours and then loses strength. By the time it is excreted in urine or feces, the radioactivity is greatly reduced or negligible. Technetium (Tc 99m) is one of the most common radionuclides. Others include isotopes of iodine, xenon, gallium, indium, and thallium for scans of specific organs or locations. In nuclear scanning, the radioisotope that is bound to a specific compound is called a radiopharmaceutical. When administered orally or intravenously to the patient, the radiopharmaceutical is taken up or absorbed by the target tissue or organ. The targeted tissue concentrates the radiopharmaceutical and emits radiation that is detected and imaged by the scanner or camera. Some of these scans, their purposes, and the pertinent patient care information are presented in Table 11.

Table 11 Selected Nuclear Scans

Name of Scan	Purpose	Special Patient Care Measures
Brain scan (positron emission tomography [PET] scan)	To evaluate brain tissue metabolism and function, with detection of abnormalities such as dementia, stroke, atherosclerosis, epilepsy, Alzheimer’s disease; to identify size and shape of brain, with detection of tumor, hematoma, cyst, atrophy, or edema	Fasting is required for 4-6 hours before the test; water and medications are permitted; Only gold members can continue reading. Log In or Register to continue Share this: Click to share on Twitter (Opens in new window) Click to share on Facebook (Opens in new window) Related Related posts: K Specimen collection procedures S A Stay updated, free articles. Join our Telegram channel Join Tags: Saunders Nursing Guide to Diagnostic and Laboratory Tests Feb 18, 2017 | Posted by admin in NURSING | Comments Off on N Full access? Get Clinical Tree Get Clinical Tree app for offline access Get Clinical Tree app for offline access