RESEARCH - Diurnal variation in serum levels of COMP in individuals with knee OA or RA

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Ann Rheum Dis. 2006 May 17; [Epub ahead of print]

Diurnal variation in serum levels of cartilage oligomeric matrix protein

(comp) in individuals with knee osteoarthritis or rheumatoid arthritis.

Andersson ML, sson IF, Karlsson K, Jonsson NE, Mansson B, Heinegard D,

Saxne T.

Spenshult's Hospital for Rheumatic Diseases, Sweden.

OBJECTIVE: The objective of this study was to monitor changes in serum

concentrations of cartilage oligomeric matrix protein (COMP) during a

24-hour period to determine any diurnal variation and estimate the half-

life of COMP in the circulation in patients with symptomatic knee

osteoarthritis (OA) and in patients with rheumatoid arthritis (RA). METHODS:

Serum samples were drawn every 4 hours (7 samples/individual over 24 hours)

in ten individuals with knee OA and 14 individuals with RA. OA was defined

radiographically and clinically (ACR criteria) and RA according to the 1987

ACR criteria. Serum COMP was measured by sandwich-ELISA (AnaMar Medical,

Lund, Sweden). A statistical model for the diurnal variation of the COMP

levels was developed using the computer program NONMEM RESULTS: No

significant changes in the COMP levels were observed during daytime between

8 AM and 9 PM in either group. A significant decrease in serum COMP was

apparent during bed rest at night reaching the lowest levels between 4 and 5

AM (p<0.03 or better vs. all other time points) in both OA and RA patients.

From the rate of decreasing serum COMP levels, a putative half- life of COMP

in the circulation was estimated to be 7.4 hours.

CONCLUSION: During normal daytime activities serum COMP levels are constant.

The decrease during the night indicates a rapid elimination of COMP once it

has reached the circulation. The stable COMP levels during the day suggest

that it is not necessary to further standardise the time of serum sampling

in clinical practice.

PMID: 16707535

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve & db=PubMed & list_uids=1\

6707535

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