The International Osteoporosis Foundation and European Calcified Tissue Society Working Group proposed a screening strategy measuring certain bone turnover markers in patients who have initiated oral bisphosphonate therapy for postmenopausal osteoporosis as a practical way to identify low adherence. The recommendations have been published in Osteoporosis International

About half of patients who start treatment for osteoporosis do not adhere to their prescribed regimen and/or discontinue within one year. Low adherence impacts the efficacy of treatment and places patients at a higher risk of fractures. Currently, there is no clear screening strategy for assessing compliance in these patients.

Bone turnover markers can indicate the early effect of the drug on bone tissue. If a low response is seen shortly after treatment initiation, this can reflect the patient’s low adherence or indicate an underlying cause of reduced response to medication. 

The Working Group based their recommendations from the findings of the TRIO Study. They recommend measuring serum PINP (procollagen type 1 N-terminal propeptide) and CTX (collagen type 1 C-terminal telopeptide) levels at baseline and after three months of starting treatment. Evaluation at three months is ideal because the first weeks after being prescribed the medication are when patients are most likely to exhibit primary non-adherence. 

In addition, the Working Group recommends that in patients where the decrease of PINP and CTX does not exceed the least significant change (38% and 56%, respectively), clinicians should reassess adherence or consider possible secondary osteoporosis. Detection rate for the measurement of PINP is 84% and for CTX is 87%. If variation in at least one marker is considered when measuring both, the level of detection is 94.5%.  

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