The nurse is caring for an infant suspected of having severe combined immunodeficiency (SCID). Which diagnostic test should the nurse anticipate being prescribed for the infant?

Explanation: The correct answer is b. Genetic or inherited defects. Immunodeficiency disorders are primarily caused by genetic mutations or defects that result in a weakened or impaired immune system.

Incorrect choices:

a. While environmental factors can contribute to the development of secondary immunodeficiency disorders, they are not the primary cause of most immunodeficiency disorders.

c. Autoimmune reactions are not the primary cause of immunodeficiency disorders. Autoimmune disorders involve the immune system attacking the body's own tissues, not a deficiency in the immune system.

d. Excessive production of white blood cells is not the primary cause of immunodeficiency disorders. In fact, immunodeficiency disorders are characterized by a deficiency or impairment of white blood cells, which are essential components of the immune system.

Explanation: The correct answer is d. Selective IgA deficiency. This disorder is characterized by a lack of immunoglobulin A, which can lead to an increased susceptibility to infections, particularly in the respiratory and gastrointestinal tracts.

Incorrect choices:

a. Selective IgM deficiency is a rare immunodeficiency disorder characterized by a lack of immunoglobulin M (IgM), not IgA.

b. X-linked agammaglobulinemia is a primary immunodeficiency disorder caused by a mutation in the BTK gene, resulting in a deficiency of B cells and immunoglobulins.

c. Common variable immunodeficiency (CVID) is a heterogeneous group of disorders characterized by decreased levels of immunoglobulins, including IgA, IgG, and IgM.