Macroprolactin/TSH by Gel Filtration Chromatography (GFC)

Clinical use:
Exclusion of Macroprolactin (Prolactin:Ig) complex as a cause of factitious hyperprolactinaemia

Macroprolactin is a high molecular mass complex of prolactin and immunoglobulin, which is typically biologically inactive but can cross-react in many serum prolactin assays. Identification of macroprolactin can prevent unnecessary or invasive investigation of hyperprolactinaemia. The assay is provided as a three tier system: 1 The serum is analysed using an assay with low cross-reactivity to macroprolactin 2 The assay is repeated after PEG precipitation of high molecular mass complex in serum 3 Equivocal samples are analysed by Gel Filtration Chromatography.

Patient Preparation
Serum prolactin is often elevated by stress. Ideally the patient should be cannulated and rested for 30 minutes before bleeding. Please discontinue anti-psychotic medication and dopamine antagonists where possible, otherwise inform SAS lab of drug history.

Sample preparation
Transfer the blood to a plain tube. Separate the serum, preferably within 30 min of collection and store at 4°C. At least 1 mL of serum is required.

Reference Ranges
Please contact SAS laboratory.

Quality Assessment
No EQAS is available. Strict internal QC procedures are followed and we operate a sample exchange system with other CPA accredited labs performing Gel Filtration Chromatography.

Centre offering this assay
Cambridge Addenbrooke’s Hospital Endocrine Laboratory

Fahie-Wilson MN, John R, Ellis AR. Related Articles, Links Macroprolactin; high molecular mass forms of circulating prolactin. Ann Clin Biochem. 2005 May;42(Pt 3):175-92

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