ECE2009 Poster Presentations Neuroendocrinology, Pituitary and Behaviour (74 abstracts)
Immunoassay determination of macroprolactin in hyperprolactinemic patients: an interassay comparative study
Mariana Martinho 1 , Teresa Martinho 1 , Nuno Cunha 1 , Fatima Curado 1 , Leonor Gomes 2 , Frederico Valido 1 , Plamen Naidenov 1 & Fernando Rodrigues 1
1Portuguese Institute of Oncology of Coimbra, Coimbra, Portugal; 2Coimbra’s University Hospital, Coimbra, Portugal.
Prolactin is mainly found in the monomeric form although it can also occur in the big-PRL and bigbigPRL (bbPRL) form: a complex of prolactin and immunoglobulin G. The latter has reduced bioactivity despite maintaining its imunorreactivity. This can cause false positive results representing the main cause of interassay variability in prolactin measurement. It should therefore be considered in every study concerning hyperprolactinemia. We aimed to evaluate the prevalence of bbPRL in a sample of patients with hyperprolactinemia and to investigate its interference in two immunoassay systems: IMMULITE2000 and KRYPTOR.
Retrospective analysis of seventy-four samples of patients with hyperprolactnemia was undertaken. The mean age was 44±12.6 years; seven patients were males. Prolactin was measured with an immunometric chemiluminescent (IMMULITE2000) and an immunofluorescent (KRYPTOR) method; additionally, bbPRL was precipitated using polyethyleneglycol (PEG) followed by prolactin measurement in the supernatant with IMM2000. We considered bbPRL to cause interference when the percentage of recuperated prolactin was fewer than 40%.
In nineteen patients the hyperprolactinemia was due to bbPRL; in one case there was an excess of prolactin monomers simultaneously. In those patients with macroprolactinemia, the mean values found by IMM2000, KRYPTOR and PEG where, respectively, 47.6±21.9; 17.5±10.9 and 10.1±8.2 ng/ml (P<0,05).
In conclusion, KRYPTOR has less immunorreactivity than IMM2000. Measurements after PEG precipitation were useful in the diagnosis of macroprolactinemia allowing, in this sample, to alter the management of 26% of patients.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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