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Test Code PINP Procollagen I Intact N-Terminal, Serum

Reporting Name

Procollagen I Intact N-Terminal, S

Useful For

Aiding in monitoring antiresorptive and anabolic therapy in patients with osteoporosis

 

An adjunct in the assessment of conditions associated with increased bone turnover, such as Paget disease

 

This test should not be used as a screening test for osteoporosis in the general population.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Serum


Ordering Guidance


This test should not be requested in patients who have recently received radioisotopes, therapeutically or diagnostically, because of potential assay interference. A recommended time period before collection cannot be provided, as it depends on the isotope administered, the dose given, and the clearance rate in the individual patient. Specimens will be screened for radioactivity prior to analysis. Radioactive specimens received in the laboratory will be held and assayed after the radioactivity has sufficiently decayed. This will result in a test delay.



Specimen Required


Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial.


Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Frozen (preferred) 180 days
  Ambient  7 days
  Refrigerated  7 days

Reference Values

Adult male: 22-87 mcg/L

Adult female premenopausal: 19-83 mcg/L

Adult female postmenopausal: 16-96 mcg/L

Reference values have not been established for patients who are younger than 18 years of age.

Day(s) Performed

Tuesday, Thursday

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

83519

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PINP Procollagen I Intact N-Terminal, S 47255-5

 

Result ID Test Result Name Result LOINC Value
61695 Procollagen I Intact N-Terminal, S 47255-5

Clinical Information

Procollagen type I propeptides are derived from collagen type I, which is the most common collagen type found in mineralized bone. In bone, collagen is synthesized by osteoblasts in the form of procollagen. This precursor contains a short signal sequence and terminal extension peptides: amino-terminal propeptide (PINP) and carboxy-terminal propeptide. These propeptide extensions are removed by specific proteinases before the collagen molecules form. Both propeptides can be found in the circulation and their concentration reflects the synthesis rate of collagen type I. Although collagen type I propeptides may also arise from other tissues (such as the skin, vessels, fibrocartilage, and tendons), most nonskeletal tissues exhibit a slower turnover than bone and contribute very little to the circulating pool of PINP. PINP is considered the most sensitive marker of bone formation, and it is particularly useful for monitoring bone formation therapies and antiresorptive therapies; it is recommended that the test be performed at baseline before starting osteoporosis therapy and performed again 3 to 6 months later.

Interpretation

This assay is specific for the intact trimeric form of procollagen type I N-terminal propeptide (PINP). When monitoring response to osteoporosis treatment, a change of greater or equal to 21% (least significant change) from baseline PINP levels (ie, prior to the start of therapy), 3 to 6 months after initiation of therapy indicates an adequate therapeutic response.

 

The direction of the change in PINP levels (decrease or increase) will depend on the type of osteoporosis treatment. In patients taking bisphosphonates, PINP levels have been shown to decrease up to 70% from baseline after 6 months of therapy. Treatment with hormone replacement therapy also shows a decrease in PINP levels but to a lesser degree than bisphosphonates therapy.

 

In patients treated with teriparatide (recombinant human parathyroid hormone 1-34), PINP levels increase from baseline, reflecting the stimulatory effect of teriparatide on osteoblasts and bone formation. PINP levels have been shown to significantly increase as early as 1 month after teriparatide treatment, peaking at 6 months following treatment. Increases greater than 10 mcg/L have been reported in 77% to 79% of teriparatide-treated patients after 3 months of therapy and are considered a successful response.

Method Description

The procollagen I intact N-terminal (PINP) kit is based on the competitive radioimmunoassay technique. A known amount of labeled PINP and an unknown amount of unlabeled PINP in the sample compete for a limited number of high-affinity binding sites of the polyclonal rabbit anti-PINP antibody. A second antibody, directed against rabbit IgG and coated Kaolin particles, is used to separate the antibody-bound PINP from free PINP. The radioactivity of the bound tracer antigen is measured on a gamma counter. The amount of labeled PINP in the sample tube is inversely proportional to the amount of PINP in the sample. The concentrations in unknown samples are obtained from a calibration curve, which is based on the concurrent testing of PINP calibrators.(Package insert: UniQ PINP RIA, Intact N-terminal propeptide of type I procollagen. Orion Diagnostica; 03/2016)

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Secondary ID

61695

Method Name

Radioimmunoassay (RIA)