L'utilizzo delle DDD reference based per la valutazione della compliance terapeutica nel trattamento con statine^*

Treatment with statins. Compliance evaluation using reference based DDDs

Introduction

Compliance is crucial in the treatment with statins. It is generally evaluated by comparing the daily dose received on average by treated patients with a standard parameter, which is often the corresponding DDD (Defined Daily Dose) issued by WHO (World Health Organisation).

Materials and methods

As regards statins, the DDDs issued by WHO (which will be hereafter referred to as WHO-DDDs) have shown to be poor indicators of a correct dosing (which they generally underestimate). As an alternative evaluation standard, reference based DDDs were drawn, for this study, from NCEP (National Cholesterol Education Program) guidelines, i.e. from in progress clinical research on efficacy and safety of statins. This multicenter, retrospective study is based on a statistical sample including six ASLs (ASL: Azienda Sanitaria Locale, Local Health Unit), located in as many Italian Regions, on the whole providing health care for 2,625,000 people. Subjects were eligible to whom statins had been prescribed at least once in the period 2001-2005 (observation period).

Results

Data relative to 294,295 patients were selected from the ASL administrative databases. Sampled patients were aged 61 on average and 48% males. The patient's compliance (measured as the ratio between the average daily dose and the reference based DDD) increased on the whole from less than 40% to more than 50% in the observation period. (Had the compliance been evaluated with WHO-DDDs, the analogous values would have been 85% and 100%). The compliance was analysed through appropriateness bands. In particu-lar, the frequency of quite incorrectly-treated patients (compliance up to 25%) decreased from 65% to 50% of the whole sample, while the frequency of patients in the optimal treatment band (75% to 100% compliance) soared from 3% to 10%.

Discussion and conclusions

The ASLs were chosen based on availability and reliability criteria, which resulted in their being concentrated in the Northern-Central part of Italy (with the Marche Region weighing more than half of the sample). They could nevertheless be considered as fairly representative of the whole country. The compliance constantly improved during the observation period, even if it reached (only) 50% on the overall average in 2005. If the WHO-DDDs had been used, the compliance would have been too optimistically evaluated, even suggesting an over-treatment area with statins (resulting in the high frequency of patients included in the band with more than 100% compliance).