What test is used during pregnancy as a screening for Down syndrome?
Percutaneous umbilical blood sampling
Alpha fetal protein analysis
Amniocentesis
Chorionic villus sampling
The Correct Answer is B
Rationale:
A. Also called cordocentesis, this is an invasive diagnostic test used to detect fetal blood disorders or infections. It is not typically used for routine Down syndrome screening because it carries higher risks and is done later in pregnancy.
B. Alpha-fetoprotein (AFP) analysis is part of the maternal serum screening (quad or triple screen) performed during the second trimester. Abnormal levels of AFP, along with other markers such as human chorionic gonadotropin (hCG) and unconjugated estriol, can indicate an increased risk for Down syndrome, neural tube defects, or other fetal abnormalities. AFP screening is noninvasive and widely used for early detection of chromosomal anomalies.
C. Amniocentesis is a diagnostic test, not a screening test. It involves sampling amniotic fluid to detect chromosomal abnormalities, genetic disorders, or infections. While highly accurate for Down syndrome, it is invasive and carries a small risk of miscarriage, so it is typically offered after an abnormal screening test or for high-risk pregnancies.
D. Chorionic villus sampling (CVS) is also a diagnostic procedure, performed in the first trimester by sampling placental tissue. Like amniocentesis, it confirms genetic conditions such as Down syndrome but is not a routine screening test.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Rationale:
A. Seasonal allergic rhinitis is a type I hypersensitivity reaction, which is IgE-mediated. It occurs when allergens trigger histamine release from mast cells, causing sneezing, itching, and nasal congestion.
B. Systemic lupus erythematosus (SLE) is a type III hypersensitivity reaction, characterized by the formation of immune complexes (antigen-antibody complexes) that deposit in tissues such as the kidneys, joints, skin, and blood vessels. These complexes trigger inflammation and tissue damage through complement activation and recruitment of inflammatory cells. Common manifestations include arthritis, nephritis, rashes, and vasculitis.
C. Poison ivy causes a type IV hypersensitivity reaction, also called a delayed-type hypersensitivity, which is cell-mediated rather than antibody-mediated. The reaction occurs 24–72 hours after exposure and involves T lymphocytes responding to the allergen.
D. Acute hemolytic blood transfusion reactions are type II hypersensitivity reactions, which are antibody-mediated cytotoxic reactions. Preformed antibodies bind to donor red blood cells, leading to cell lysis and hemolysis.
Correct Answer is B
Explanation
Rationale:
A. This describes autoimmune disorders, where the immune system attacks the body’s own tissues. Autoimmunity is not the cause of primary immunodeficiency, although some immune deficiencies can increase the risk of autoimmune disease.
B. Primary immunodeficiency results from genetic defects or congenital abnormalities that lead to loss or dysfunction of one or more components of the immune system, such as B cells, T cells, phagocytes, or complement proteins. Examples include severe combined immunodeficiency (SCID), X-linked agammaglobulinemia, and DiGeorge syndrome. These deficiencies predispose individuals to recurrent infections, often starting in infancy or childhood.
C. Hypersensitivity reactions are exaggerated immune responses to antigens, classified as types I–IV, and are not the underlying cause of primary immunodeficiency.
D. An excessive immune response can result in allergies, hypersensitivity, or autoimmunity, but primary immunodeficiency is caused by loss of immune function, not overactivity.
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