|
| |
Determination of thyroid peroxidase (TPO) antibodies has been improved
by introduction of quantitative assays (RIA, IRMA, ELISA) and the use of
purified human or recombinant TPO as the antigen. The reference preparation
used is the Medical Research Council (MRC) 66-387. Compatibility of different
assays is still impaired owing to the presence of an individual antibody
spectrum showing variable nonparallel reactivity with the same antigen.
TPO antibodies are found to be present in about 90% of patients with
autoimmune thyreoiditis (Hashimoto thyroiditis and primary myxedema) and
about 75% of patients with active Graves' disease. Interestingly, TPOAb
can be detected also in patients with non-immune thyroid diseases or even
in older persons without evidence of thyroid disorders. This limited specificity
of TPOAb determination may be overcome by higher cut-off values, which
result, however, in a reduced sensitivity in the diagnosis of clinical
autoimmune thyroid disease (Table 6). TPOAb may also be detected in association
with other autoimmune disorders like insulin dependent diabetes mellitus
(IDDM), Addisons' disease or systemic lupus erythematodes.
| Table 6: |
Incidence of elevated titres of TPOAb in patients with
various thyroid diseases and in healthy controls at different cut-off values |
|
|
100 mU/l |
>200 mU/l |
>500 mU/l |
|
|
| Grave's Disease |
|
before antithyroid treatment
|
n = 51 |
76% |
67% |
53% |
|
after 3-12 months of antithyroid treatment
|
n = 75 |
68% |
60% |
47% |
|
|
| Hashimoto thyroiditis and primary myxedama |
n = 35 |
89% |
77% |
63% |
| Autonomously functioning nodules |
n = 51 |
16% |
10% |
6% |
|
|
| Nontoxic goiter |
n = 41 |
2% |
0% |
0% |
|
|
| Healthy controls |
|
<= 60 y
|
n = 36 |
0% |
0% |
0% |
|
> 60 y
|
n = 33 |
12% |
6% |
3% |
|
|
|
|
