Re: What does low Iga (Iga [equ] o.1) mean?

As with all medical questions referring to a specific patient, the 
best answer is to ask the doctor looking after you; they can explain 
this finding in relationship to you personally.

IgA usually stands for immunoglobulin A, one of the classes of immunoglobulins
(also called antibodies) that are in the blood. IgA is important in
protecting 'mucosal surfaces' - the linings of the tracts of the body, eg the 
lungs, and is secreted in saliva and tears.

The statement you provide MIGHT mean that the serum IgA (immunoglobulin A)
level is 0.1 g/litre.
Again, you would have to check with the referring laboratory, since the 
'normal' range varies from lab to lab, but 0.1 is generally fairly low.
They may have done a special 'low IgA' measurement, since IgA is difficult
to estimate accurately at low levels. 

The significance of a low (but not absent) IgA is doubtful - there is a
condition called selective IgA deficiency, usually defined as IgA of <0.05 (essentially zero).
This is often a chance finding in approx 1 in 400 caucasians - who often
have no symptoms. The symptoms of true IgA deficiency can include recurrent
bacterial infections, an increased incidence of allergies, and
an increased incidence of autoimmune disease. A clinical immunologist might
do some further investigations such as measuring other antibodies
(IgG, IgM, subclasses of IgG) - but would really have to base their
investigations on the clinical situation presented to them. An IgA level 
of 0.1 does not make the diagnosis selective (total) IgA deficiency.

More information can be found in any textbook of clinical immunology, and
there's a useful facts sheet at
http://www.mssn.edu/peds/modell/iga-defi.html