12
Diagnosis
Table 3. Summary of Laboratory Findings in the Diagnosis
of Antibody Deficiencies
IgG IgA IgM
IgG
subclass
Vaccine
response
B
cells Diagnosis
NL NL NL NL NL NL
Normal
a
NL NL NL NL
Low
b
NL SAD
NL NL NL ≥1 Low
Low
b
NL IGGSD
NL Absent NL Normal NL or
low
NL SIGAD
NL Absent NL ≥1 Low
Low
b
NL IgA deficiency with
IGGSD
Low NL NL NL NL Possible secondary,
unspecified, or transient
hypogammaglobulinemia
c
Low NL or
low
NL or
low
NL NL or
low
Unspecified or transient
hypogammaglobulinemia
Low Low NL or
high
Low NL HIM
Low Low NL or
low
Low
d
NL or
low
CVID, possible transient
hypogammaglobulinemia
Absent Absent Absent Absent Agammaglobulinemia or
severe CVID
e
e clinical presentation is primarily suggestive of an antibody defect or any evaluation
of cellular function is thus far normal, and the clinical presentation is at least consistent
with a possible antibody deficiency and not suggestive of a cellular component (e.g., lack
of opportunistic infections). e initial laboratory examination of humoral immunity
consists of measuring levels of various immunoglobulin isotypes (IgG, IgA, IgM, and
possibly IgG subclasses) in serum, as well as a measure of function or specific antibody
production, which should include both protein and polysaccharide antigens (see SS 6).
a
Consider complement deficiency or phagocyte defect.
b
Usually refers to polysaccharide response.
c
In this circumstance it is useful to measure serum total protein and/or albumin levels. If low, this is
consistent with secondary hypogammaglobulinemia.
d
Protein and/or polysaccharide response.
e
Cellular immunity should be evaluated as indicated by other clinical features but is oen worth
considering when significant impairment of humoral immunity is observed because it could be a
component of a CID.
