Biochemical markers of bone turnover decrease rapidly (within three months) after initiation of antiresorptive drugs such as oral or IV bisphosphonates, denosumab or raloxifene, and increase with commencement of osteoanabolic therapies.5–8 They have also been shown to provide information on the antifracture efficacy of these agents.8,9 For these reasons, bone turnover markers may be used to assess the effect of therapy on bone metabolism.
Measuring a bone resorption marker (e.g., serum C-telopeptide) after three months of antiresorptive treatment and finding a level in the lower half of the premenopausal range generally indicates adherence with antiresorptive therapy. However, in the absence of clear evidence of improved patient outcomes from the use of bone resorption markers, as well as cost-effectiveness data, their routine use in patient monitoring in general practice is not recommended.
Evidence Statement
Failure to observe an increase in BMD during therapy with bisphosphonates, denosumab, or raloxifene does not indicate decreased antifracture efficacy of the drug and is no indication to change treatment.10–15 A stable or increasing BMD during treatment should be considered as adequate therapy response.10,12–16 In contrast, detectable loss of BMD while on antiresorptive treatment may be associated with negative clinical outcomes (increased fracture risk) and should prompt review of diagnosis, treatment regimen, and patient medication adherence.2,17
A decision to change treatment based solely on a new fracture occurring during treatment is not supported by RCT data. Because fractures will occur in some individuals even on effective therapy, fracture per se is not an indication to change. However, patient tolerance, treatment adherence, and side effect profile may suggest changing the type or route of administration of therapy on an individual basis. Evidence of lack of response (e.g., falling BMD or failure to achieve expected changes in bone turnover markers) could justify a change. However, adherence with, and the correct mode of taking medications should be evaluated first, because problems with these aspects are the most likely explanation. Although long-term adherence with non-pharmacological and pharmacological interventions is crucial, it is often low, even in patients with fractures.18,19
Follow-up visits, close contact between patient and health professionals, and repeat BMD and/or bone turnover marker measurements, may be used to improve medication adherence. In a British study, review of results of serial BMD and/or bone turnover marker measurements between nurse and patient, or doctor and patient, resulted in improved adherence to, and persistence with, medication.20 However, there is no current consensus on the use of surrogate parameters to increase patient treatment adherence. Three major international guidelines recommend follow-up to ensure that treatment is effective. Regular monitoring is an important component of any osteoporosis treatment plan.21–23 This applies to at-risk patients whether or not they are on bone-protective drug treatment. Follow-up BMD testing and physician check-ups are also recommended.21–23
Patients with an increased risk of fracture at initial examination should be re-evaluated at regular intervals for implementation of non-pharmacological measures, risk factors, and fracture risk. Because a decrease in BMD below measurement error before two years is unlikely, follow-up BMD examinations are usually not recommended at intervals of less than two years.24 Repeat DXA scans at intervals of two years or longer are appropriate when the efficacy of treatment, risk assessment, or decision to change or interrupt treatment is being considered.24 Repeat scans may also be useful for addressing patient concerns in relation to treatment adherence. Change in BMD may be difficult to interpret if less than the precision error (2.8×precision measured as the standard deviation or coefficient of variation of repeat measurements). Pretest probability, as well as concordance of change at different skeletal sites, assists in determining a significant change.
After initiating a specific pharmacological intervention, clinical examinations are recommended after 3–6 months and after 6–12 months. This may include documenting pain, functionality, weight, and height.22 Ongoing monitoring of patients taking medication, particularly those taking oral bisphosphonates, should be conducted to ensure adherence with administration instructions. Laboratory tests may be used to identify drug-induced side effects or potentially treatable conditions contributing to the patient’s bone health (e.g., low vitamin D or thyroid disease).