Objective:

It is estimated that in one year between 50-60% of patients treated with osteoporosis drugs are non-compliant. There are different indirect methods of assessing compliance. Our objective is to test a single determination of the carboxyterminal telopeptide of type I collagen (CTX) to assess compliance in patients treated with bisphosphonates, either on its own or together with the Morinsky-Green questionnaire.

Material and method:

A diagnostic assessment study was carried out in 10 centers in Catalonia. Through consecutive sampling, postmenopausal women with osteoporosis were selected and treated with the same antiresorptive drug in the last year. Those treated with a drug other than bisphosphonate, with cognitive impairment, terminal illness, advanced renal failure or fracture in the previous year, were excluded. Data were collected on the diagnosis of osteoporosis and type of treatment. Analysis was requested with CTX determination. As a gold standard, the medication possession rate (MPR) was used. Using the ROC curve methodology, the theoretical CTX cut-off point was established. Sensitivity, specificity and positive predictive values were calculated to estimate therapeutic compliance.

Results:

100 patients were included, of which more than half were being treated with alendronate. According to the MPR, 70% were compliant. The mean CTX value was 0.193±0.146 ng/ml. It was lower in the compliant patients. A value of 0.196 ng/ml was established as a cut-off point to assess compliance. The joint assessment of the CTX together with the Morinsky-Green questionnaire showed greater discriminatory capacity.

Conclusions:

Carrying out a single determination of CTX (<0.196 ng/ml) along with the Morinsky-Green questionnaire allows us to more accurately assess the therapeutic compliance in patients treated with bisphosphonates.

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