Abstract
BackgroundMacroprolactin is responsible for pseudohyperprolactinemia and is a common pitfall of the prolactin immunoassay. We aimed to determine the frequency of macroprolactinemia in Chinese hyperprolactinemic patients using monomeric prolactin discriminated by precipitation with polyethylene glycol (PEG).MethodsPost-PEG monomeric prolactin gender-specific reference intervals were established for the Elecsys immunoassay method (Roche Diagnostics) using sera from healthy female (n = 120) and male (n = 120) donors. The reference intervals were validated using 20 macroprolactinemic (as assessed by gel filtration chromatography (GFC)) sera samples, and presence of monomeric prolactin was discriminated by GFC. Patients with high total prolactin were then screened by PEG precipitation to analyze macroprolactin. The demographic and biochemical details of patients with true hyperprolactinemia and macroprolactinemia were compared.ResultsReference intervals for monomeric prolactin in females and males were 3.4–18.5 and 2.7–13.1 ng/mL, respectively. Among 1140 hyperprolactinemic patients, macroprolactinemia was identified in 261 (22.9 %) patients while the other 879 (77.1 %) patients were diagnosed with true hyperprolactinemia. Menstrual disturbances were the most common clinical feature in both groups. Galactorrhea, amenorrhea, and visual disturbances occurred more frequently in true hyperprolactinemic patients (P < 0.05).ConclusionsThe prevalence of macroprolactin in Chinese patients with hyperprolactinemia was described for the first time. Monomeric prolactin concentration, along with a reference interval screening with PEG precipitation, provides a diagnostic approach for hyperprolactinemia with improved accuracy.
Highlights
Heterogeneity has been described in the molecular size of prolactin in the majority of serum samples from healthy individuals and patients with hyperprolactinemia
By gel filtration chromatography (GFC), we identified 20 macroprolactinemia samples (15 female, five male) from 95 patients whose sera indicated the presence of biochemical hyperprolactinemia before polyethylene glycol (PEG)-precipitation
Reference intervals of post-PEG serum monomeric prolactin Data were collected from eligible participants, including 120 females and 120 males
Summary
Heterogeneity has been described in the molecular size of prolactin in the majority of serum samples from healthy individuals and patients with hyperprolactinemia. Patients with macroprolactinemia experience mild and nonspecific symptoms of hyperprolactinemia [3] In these patients, monomeric prolactin concentrations are within reference values and most macroprolactin is confined to the vascular system, where it is biologically inactive [5]. Macroprolactin poses a major problem due to its interference with prolactin assays. This commonly results in misdiagnosis and mismanagement of patients, as well as wasted healthcare resources and unnecessary concern from both patients and clinicians [6]. High concentrations of macroprolactin appears to result from reduced clearance of antigen-antibody complexes of monomeric prolactin and immunoglobulin G. We aimed to determine the frequency of macroprolactinemia in Chinese hyperprolactinemic patients using monomeric prolactin discriminated by precipitation with polyethylene glycol (PEG)
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