Newborn screening Flashcards
Timeline of newborn screen
typically performed 24 to 48 hours after birth to screen newborns for a series of severe diseases
results from a newborn screen can take ~7 days to return and certain diseases may present before the screening results are available.
If a test is positive the physician caring for mother and child will be notified and results are discussed with parents regarding next steps, including making a definitive diagnosis.
Logistics of newborn screen
The state of Kentucky currently tests for 57 different conditions.
The fee for newborn screening is $123 and is usually a part of the cost of a newborn’s hospital stay
Can opt out on religious grounds but has to be a written petition
Some of the disorders in newborn screening require specialized tests, whereas most metabolic diseases are screened by analyzing blood obtained from a heel prick.
Screening for Critical Congenital Heart Disease
Using a pulse oximeter
ulse oximetry involves placing non-invasive oxygen sensors on the infant’s hand and foot to monitor oxygen saturation of the infant’s blood in the two locations.
Pulse oximetry involves monitoring both the total % oxygen saturation and the difference in oxygen saturation (of hemoglobin) between the hand and foot. Values below fixed percentages in either test can trigger additional testing.
Congenital hearing loss screening
Congenital hearing loss screening tests are non-invasive and include:
Otoacoustic emissions (OAE), which examines the inner ear response to sound.
Auditory brainstem response (ABR) - measures brainwave activity in response to sound including the major auditory center in the brainstem.
If not caught early and treated appropriately can lead to delays in speech or language acquisition.
How are newborn blood screens performed
The majority of diseases screened for in newborns are carried out through the analysis of blood obtained from a heel prick and placed on Guthrie cards
Punch discs from the Guthrie cards are placed in solutions where metabolites are extracted and subsequently analyzed by Liquid Chromatography and Mass Spectroscopy (LC-MS/MS).
The analytes are generally metabolites that increase in amount because they are substrates for a defective enzyme responsible for a disorder
What is the guthrie test
β-2-thienylalanine could inhibit the growth of Bacillis subtilis and that this inhibition could be overcome by high levels of phenylalanine.
Types of Amino Acid Metabolism disorders
amino acid disorders, organic acid disorders, or urea cycle disorders
Defined by elevated analyte caused by enzyme disorder
If it is an amino acid, it is an amino acid disorder.
If the metabolite is further down the catabolic pathway of an amino acid and it is no longer an amino acid but yet is still an acid, the disorder then becomes an organic acid disorder.
How ae Hemoglobinopathies screened for
Hemoglobinopathies are screened for by electrophoresis or high-pressure liquid chromatography (HPLC)
How are Endocrinopathies screened for
Endocrinopathies are screened for measuring levels of appropriate hormones
Congenital adrenal hyperplasia (CAH)
Analyte 17-hydroxyprogesterone
Congenital hypothyroidism (CH)
Analytes TSH and T4
How is Cystic Fibrosis tested for
Cystic fibrosis is tested for genetically or by an immunologic test for the presence of immuno-reactive trypsinogen (IRT) in the blood
How are Immunologic disorders screened for
Immunologic disorders are screened for by a surrogate measure of T cells levels referred to as T cell receptor excision circles (TREC).
