Procollagen-3 N-Terminal Peptide (P3NP)

P3NP measured by radioimmunoassay.
Clinical details: 
Collagen is formed initially with propeptides at both ends. In the liver the majority of collagen is either type 1 or type 3. The removal of the propeptides promotes development of collagen fibrils. The propeptides may either be retained in the matrix or released into the circulation. Fibrosis occurring in the liver results in the deposition of collagen and release of propeptides, predominantly P3NP. Increased P3NP is seen in various liver diseases in which fibrosis/cirrhosis is a major feature e.g. alcoholic liver disease, primary sclerosing cholangitis and also in non-liver diseases where fibrosis is a feature e.g. myelofibrosis, systemic sclerosis etc.

Methotrexate is a successful form of treatment for psoriasis and rheumatoid arthritis (RA). It has, however, been noted that prolonged exposure can result in irreversible hepatic fibrosis, the risk of which is idiopathic but associated with cumulative doses of more than 1.5g (usually encountered in psoriasis as lower doses are used in RA). Previously it was advised that a liver biopsy be considered after each cumulative 1.5g methotrexate. In 1996 it was shown that serum P3NP concentrations were predictive of the development of hepatic fibrosis. Continually raised P3NP concentrations were found to be associated with fibrosis in 78-100% of cases, but were only seen in 15-18% of subjects with a normal liver on biopsy. Current guidelines issued by the British Association of Dermatologists (2016) on the use of methotrexate in psoriasis suggest P3NP measurements be carried out annually and three monthly after a raised value. At Viapath, we use guideline-recommended radioimmunoassay.

In adults with psoriasis receiving methotrexate, P3NP results should be interpreted as follows:
- If P3NP is greater than 4.2 μg/L for the first time: repeat test in 3 months.
- If P3NP is raised:
> 8 μg/L on two occasions; or
> 4.2 μg/L but < 8.0 μg/L on three occasions within 12 months; or
> 10 μg/L on one occasion
results may indicate liver fibrosis - suggest onward referral for specialist advice.

Reference range: 

The normal ranges for serum P3NP are as follows:

0-3 years              3.4 - 52.6 μg/L

4-9 years              3.4 - 12.1 μg/L

10-16 years          2.9 - 24.4 μg/L

17-18 years          2.0 - 7.0 μg/L

>19 years             1.2 - 4.2 ug/L

Sample type and Volume required: 
Serum (500 µL).
Turnaround time: 
Results within 7 working days
Storage and transport: 
Stable at 2-8 °C for up to 5 days, store at -20 °C for longer periods. Send by overnight first class post. If possible, please complete the request form attached and send as a hard copy (do not send electronically) with the sample. This will ensure all relevant information is available and will aid us in processing your test.
Reference Biochemistry Department at King's College Hospital
020 3299 4107
King's College Hospital
Denmark Hill
London SE5 9RS
Immunochemistry Laboratory at King's College Hospital
020 3299 4130
King's College Hospital
Denmark Hill
London SE5 9RS
For clinical advice or interpretation of results, please contact the laboratory in the first instance.

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Last updated: 26/06/2018