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Test ID: 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.

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 test should be performed before beginning osteoporosis treatment (ie, prior to the start of therapy) to establish a baseline procollagen type I intact N-terminal propeptide (PINP) level. Three to 6 months after initiation of therapy, a change of 21% or more (least significant change) from baseline PINP levels indicates an adequate therapeutic response. This assay is specific for the intact trimeric form of PINP.

 

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 of >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.

Analytic Time

1 day

Day(s) and Time(s) Performed

Tuesday, Thursday; 11 a.m.

Clinical Reference

1. Liberman UA, Weiss SR, Broll J, et al: Effect of oral alendronate on bone mineral density and the incidence of fractures in postmenopausal osteoporosis. The Alendronate Phase III Osteoporosis Treatment Study Group. N Engl J Med. 1995;333(22):1437-1443

2. McClung MR, San Martin J, Miller PD, et al: Opposite bone remodeling effects of teriparatide and alendronate in increasing bone mass. Arch Intern Med. 2005 Aug 8-22;165(15):1762-1768

3. Eastell R, Krege JH, Chen P, et al: Development of an algorithm for using PINP to monitor treatment of patients with teriparatide. Curr Med Res Opin. 2006 ;22(1):61-66

4. Vasikaran S, Eastell R, Bruyere O, et al: IOF-IFCC Bone Marker Standards Working Group. Markers of bone turnover for the prediction of fracture risk and monitoring of osteoporosis treatment: a need for international reference standards. Osteoporos Int. 2011;22(2):391-420

Specimen Type

Serum


Advisory Information


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 made because it will depend 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


Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Frozen (preferred) 28 days
  Ambient  7 days
  Refrigerated  7 days

Reference Values

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

Adult male: 22-87 mcg/L

Adult female premenopausal: 19-83 mcg/L

Adult female postmenopausal: 16-96 mcg/L

Test Classification

This test has been cleared, approved or is exempt by the U.S. 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 In Process

 

Result ID Test Result Name Result LOINC Value
61695 Procollagen I Intact N-Terminal, S 47255-5
Mayo Clinic Laboratories | Endocrinology Catalog Additional Information:

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