Prolactin

Label Mnemonic:	PROL
Epic code:	LAB531
Downtime form:	Doctor/Provider Orders - Pathology Core and Specialty Care Nursery

Chemistry
6240 RCP
356-3527

Specimen(s):

Plasma

Collection Medium:

Plasma Separator Tube 4.5 mL

Alternate Collection Media:

Call laboratory for additional acceptable specimen collection containers.

Minimum:

3 mL whole blood light green top tube or TWO Microtainer^® devices.

Testing Schedule:

24 hrs/day, 7 days a week, including holidays.

Turn Around Time:

1 hour (upon receipt in laboratory)

Reference Range:

Males:                   4.0 - 15.2 ng/mL
Females (not pregnant):  4.8 - 23.3 ng/mL
Age-based references ranges in children have not been established.

References ranges by Tanner stage:
  Males
    Stage I:       < or = 10.0 ng/mL
    Stage II-III:  < or =  6.1 ng/mL
    Stage IV-V:     2.8 - 11.0 ng/mL
  Females:
    Stage I:        3.6 - 12.0 ng/mL
    Stage II-III:   2.6 - 18.0 ng/mL
    Stage IV-V:     3.2 - 20.0 ng/mL

Other References Ranges:
  Cord Blood:                45 - 539 ng/mL
  Pregnancy, 3rd trimester:  95 - 473 ng/mL

Comments:

This assay may be significantly impacted by high-dose biotin (>5 mg dose) taken within previous 12 hours. High concentrations of biotin may lead to falsely decreased results. These concentrations may be found in patients taking over-the-counter supplements with biotin content much higher than nutritional requirements for biotin. Specimens should not be collected until at least 12 hours after the last dose.

As of September 14, 2010, samples that produce results above the upper limit of the gender-specific reference range are no longer screened for the presence of macroprolactin by PEG (polyethylene glycol) precipitation. If screening for macroprolactin is desired, see "Macroprolactin Check".

Test Limitations:

The assay is unaffected by icterus (bilirubin is less than 30 
mg/dL), hemolysis = 1500 (Hb is less than 1.5 g/dL), lipemia 
(Intralipid is less than 1500 mg/dL) and biotin is less than 40 ng/mL 
(criterion: recovery within plus or minus 10% of initial value).

No interference was observed from rheumatoid factor (up to approx. 
1100 IU/mL) and samples from dialysis patients.

No high dose hook effect at prolactin concentrations of 12690 ng/mL.

In vitro tests were performed on 16 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 hyperprolactinemia 
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.

Methodology:

Electrochemiluminescence Immunoassay

CPT Code:

84146