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Optimal adherence rates: how much is enough?

The short answer is : it depends.

Adherence is, by nature, a complex and variable notion. To this day, there is no commonly accepted definition of what makes a patient “adherent” or “non-adherent” in academia and businesses, which maintains a state a confusion around what is seen as satisfactory.

The definition of “adherence” highly depends on several factors.

Firstly, adherence cannot be separated from the notion of time, as the interaction between the patient and the treatment is a process: the patient has to first initiate the treatment, then to implement it according to their physician instructions, and finally to persist for the whole duration of the prescription, which can entail supplementary actions such as going to a follow-up visit or obtaining another box from their pharmacy.

Can we say that a patient who takes 90% of the prescribed doses on an irregular schedule which entails commonly taking double doses, is more adherent then a patient who takes 70% of all doses, but always at the right time? What can we say about the patient who took 100% of the doses within the prescription timeline, but with a week-long drug holiday in between?

Ultimately, “adherence” must be defined considering the drug safety profile and the specific challenges of the patient, which can be very personal.

Secondly, what can be considered satisfactory adherence depends on the type of illness that affects the patient.

The most striking example to illustrate that point is brought by contrasting HIV and diabetes patient outcomes.

Indeed, HIV patients, who are trying to limit the development of a viral infection, can only achieve positive immunological outcomes if they maintain strict adherence, which means taking more than 95% of the doses. HIV patients who took between 80 and 90% of the doses experienced a 35 to 41% drop of probability of responding well to their treatment (Lima VD and al, 2008).

While all HIV patients benefit from the highest possible adherence rates, targets are widely varying in diabetes. Numerous factors need to be considered, related to the patient’s individual health state and the complexity of the treatment. According to a more recent study, satisfactory patient outcomes could be achieved at adherence rates ranging from 46 to 94%. (Lo-Ciganic and al, 2016)

In the end, a sound adherence strategy will require a holistic analysis of the circumstances surrounding the patient group, if not the patient themselves, and of the treatment.

Monitoring and support operated with technological solutions have a role to play in understanding patterns of adherence and setting goals that will allow for the best possible patient outcomes.

If you, or your organization, are interested in adherence, or have a question/reaction to submit, do not hesitate to message me at

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