MALES: 4.0 to 15.2 ng/mL FEMALES: 4.8-23.3 ng/mL

The assay is unaffected by icterus (bilirubin is less than 30 mg/dL), hemolysis = 1500 (Hb is less than 1 g/dL), lipemia (Intralipid is less than 1500 mg/dL) and biotin is less than 100 ng/mL (criterion: recovery within plus or minus 10% of initial value). In patients receiving therapy with high biotin doses (i.e. is greater than 5 mg/day) no sample should be taken until at least 8 hours after the last biotin administration. No interference was observed from rheumatoid factor (up to approx. 1700 U/mL) and samples from dialysis patients. No high dose hook effect at prolactin concentrations of 12690 ng/mL. In vitro tests were performed on 17 commonly used pharmaceuticals. No interference with the assay was found. As with all tests containing monoclonal antibodies, erroneous findings may be obtained from samples taken from patients who have been treated with monoclonal mouse antibodies or who have received them for diagnostic purposes. In rare cases, interference due to extremely high titers of antibodies to ruthenium can occur. Prolactin contains additives which minimize these effects. Extremely high titers of antibodies to streptavidin can occur in isolated cases and cause interference. When determining prolactin it should be remembered that the measured concentration is dependent upon when the blood sample was taken, since the secretion of prolactin occurs in episodes and is also subject to a 24-hour cycle. The release of prolactin is promoted physiologically by suckling and stress. In addition, elevated serum prolactin concentrations are caused by a number of pharmaceuticals (especially dopamine receptor antagonists including antipsychotics), TRH and estrogen. The release of prolactin is inhibited by dopamine, L-dopa and ergotamine derivatives. A number of publications report the presence of macroprolactin in the serum of female patients with various endocrinological diseases or during pregnancy.(1,2) Differing degrees of detection of the serum macroprolactins (ultra-big is greater than 160 kD) relative to monomeric prolactin (22-23kD) by various immuno-assays have also been described. This could make the detection of hyperprolac tinemia dependent on the immunoassay used. The prolactin assay also encompasses macroprolactin. Accordingly, higher values may occasionally be found in patient samples than with other assay procedures. For diagnostic purposes, the prolactin findings should always be assessed in conjunction with the patient's medical history, clinical examination and other findings. (1) Dericks-Tan JSE, Siedentopf HG, Taubert HD. Discordant Prolactin Values obtained with Different Immunoassays in an infertile Patient. J Lab Med 1997;21(9):465-470. (2) Leite V, Cosby H, Sobrinho LG, Fresnoza A, Santos MA, Friesen HG. Characterization of big-big prolactin in patients with hyperprolactinoma. Clin Endocrinol 1992;37:365-372.