Criteria for Decreased Levels of Serum Immunoglobulin A (IgA Deficiency States)

Parameters:

(1) serum immunoglobulin IgA concentration in g/L

(2) mean concentration for serum IgA based on age

(3) standard deviation for serum IgA based on age

(4) age of the patient in years

(5) serum levels of IgG and IgM

lower limit of normal reference range =

= (mean for serum IgA) - (2 * (standard deviation for serum IgA))

In selective IgA or partial IgA deficiency the serum levels of IgG and IgM are normal.

A deficiency of IgA may occur alone or in combination with other immunoglobulin deficiencies.

where:

• Some laboratories might use (mean) - (2.5 * (standard deviation)) to define the lower limit of the normal reference range.

• The cutoff of < 0.06 g/L was based on the lower limit of detection with early tests. Other cutoffs are used by various authors.

• Serum IgA may be totally absent. This is the type of deficiency that can result in an anaphylactic response to blood products containing IgA.

• 0.06 g/L = 6 mg/dL.

• Serum IgA levels may be low in patients < 2 years of age in the absence of selective IgA deficiency. As the child develops IgA production may increase. The diagnosis of selective IgA should not be made until the child is >= 2 years of age (some authors use >= 5 years of age).

• IgA deficiency may be acquired with certain drugs or after some infections. The deficiency is reversible on reversal of the triggering event.