PINP and CTX make suitable reference markers for bone turnover
MedWire News: Two international organizations have called for serum procollagen type I N propeptide (s-PINP) and serum C-terminal telopeptide of type I collagen (s-CTX) to be used as reference bone turnover markers (BTMs) in clinical studies.
The recommendation is based on the findings of a literature review conducted by the International Osteoporosis Foundation (IOF) and the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) to determine the clinical potential of BTMs in the prediction of fracture risk and for monitoring the treatment of osteoporosis.
"Markers of bone turnover are biochemical products measured usually in blood or urine that reflect the metabolic activity of bone but which themselves have no function in controlling skeletal metabolism," explain Cyrus Cooper (University of Southampton, UK) and colleagues.
The researchers report that 18 of the 22 prospective studies they reviewed showed a significant association between one or more markers of bone formation (or resorption and fracture risk. Specifically, odds ratios and relative risks for fracture among patients with elevated procollagen type I N propeptide, osteocalcin, alkaline phosphatase (ALP), bone-derived ALP, and C-terminal and N-terminal cross-linking telopeptides, among others, ranged from 1.3-5.9.
Although BTMs have been used for fracture prediction in clinical practice for many years, stronger evidence for the association is still needed, as there has been inconsistency in the manner by which risk is expressed, say the team.
The researchers also found that BTMs are used worldwide for monitoring treatment in individuals with osteoporosis.
However, the review demonstrated that the clinical value of BTMs is limited by inadequate appreciation of the variability that occurs when different classes and doses of drugs are used in osteoporosis treatment. Inadequate quality control is another potential limitation, they say.
In spite of this, the authors concluded that "BTMs hold promise in fracture risk prediction and for monitoring treatment."
Therefore, "IOF and IFCC consider that reference standards for bone formation [s-PINP] and resorption markers [s-CTX] should be established and that assays based on these standards be used consistently in future clinical trials and observational studies," they write in the journal Osteoporosis International.
These two markers were selected because standardized, automated assays are widely available, and their biological and analytical variability is well documented. "The adoption of international reference standards will markedly enhance laboratory consistency and facilitate their inclusion in routine clinical practice," says the team.
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By Laura Dean