Evaluation of monomeric prolactin level by TRACE method and precipitation with polyethylene glycol

Prolactin exists in various forms including the monomeric biologically active form (23kDa) and a higher molecular weight form, bound most commonly to IgG, known as macroprolactin (>100kDa). Macroprolactin lacks biological activity and is one of the causes of false-positive results. In Russian Federation the most common method for macroprolactin determination is PEG precipitation test. We had conducted a retrospective analysis of 37 samples of patients with hyperprolactinemia (3 of them were males). The mean age was 30 [25;35] years. Prolactin level was measured by the immunoenzyme method with manual PEG precipitation and TRACE. The mean values found by the immunoenzyme method with manual PEG precipitation were 461,6 [375,0;821,2] mU/l, by TRACE - 449,9 [357,2;749,2] mU/l. The number of patients with normal prolactin levels was 30% (11) confirmed by two methods, high prolactin level at 46% (17). The prevalence of clinical symptoms of hyperprolactinemia was not differ depend the groups. The phenomenon of macroprolactinemia was registered in 32% (12) of patients. In 8 persons of this group normal prolactin level was revealed and in 4 patients hyperprolactinemia was found by TRACE. Measurements of prolactin levels by the TRACE method is useful for correct diagnosis in patients with equivocal results received by traditional method with PEG precipitation.