Diagnostic criteria for X-linked agammaglobulinemia (XLA)

Definitive diagnosis*

Male patient with less than 2% CD19+ B cells and at least one of the following:

1. Mutation in Btk.

2. Absent Btk mRNA on Northern blot analysis of neutrophils or monocytes.

3. Absent Btk protein in monocytes or platelets.

4. Maternal cousins, uncles, or nephews with less than 2% CD19+ B cells.

Probable diagnosis*

Male patient with less than 2% CD19+ B cells in whom all of the following are positive:

1. Onset of recurrent bacterial infections in the first 5 years of life.

2. Serum IgG, IgM, and IgA more than 2 SD below normal for age.

3. Absent isohemagglutinins and/or poor response to vaccines.

4. Other causes of hypogammaglobulinemia have been excluded.

Possible diagnosis*

Male patient with less than 2% CD19+ B cells in whom other causes of hypogammaglobulinemia have been excluded and at least one of the following is positive:

1. Onset of recurrent bacterial infections in the first 5 years of life.

2. Serum IgG, IgM, and IgA more than 2 SD below normal for age.

3. Absent isohemagglutinins.

CD: cluster of differentiation; BtK: Bruton tyrosine kinase; mRNA: messenger ribonucleic acid; IgG: immunoglobulin G; IgM: immunoglobulin M; IgA: immunoglobulin A; SD: standard deviation.
* Patients with a definitive or probable diagnosis are assumed to have a greater than 98 and 85% probability, respectively, that in 20 years they will still have the same diagnosis. Patients with a possible diagnosis are those that have some, but not all, of the characteristic clinical or laboratory findings of a particular disorder.

From: Conley ME, Notarangelo LD, Etzioni A. Clin Immunol 1999; 93:190.

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Diagnostic criteria for X-linked agammaglobulinemia (XLA)