Bruton Tyrosine Kinase, Protein Expression, Flow Cytometry, Blood

Clinical Use

Use

This test is useful for preliminary screening of X-linked agammaglobulinemia, primarily in male patients under the age of 65 or female carriers of child-bearing age under 45. X-linked agammaglobulinemia (XLA) is a primary immunodeficiency caused by variants in the Bruton tyrosine kinase (BTK) gene. The test assesses protein expression levels and helps in determining whether further genetic analysis is warranted. It is an essential tool for the clinical evaluation of male patients with less than 1% B cells and suspected immunodeficiency. Absence of BTK protein expression provides a strong rationale for pursuing genetic sequencing.

Special Instructions

Not provided.

Limitations

The test is only a screening tool for BTK protein expression. Approximately 20% to 30% of patients with XLA may have normal protein expression with aberrant function, undetectable by this test but identifiable through genetic sequencing. The ability to identify female carriers depends on the specific antibodies used for flow cytometry. Genetic testing provides a more definitive diagnosis and is recommended in conjunction with clinical correlation to confirm XLA.

Test Details