It’s long been accepted as standard that a drug’s target adherence rate should be 80%, but in many cases that number is just an arbitrary data point. Sometimes, lower adherence may be enough, but in more instances, a greater adherence rate is required to ensure optimal patient outcomes.

According to Terrence F. Blaschke, M.D., figuring out how much adherence is enough can come down to several factors, including the dose of the drug, its half-life, its duration of action and its forgiveness, or how long it continues to be therapeutically effective after it was last taken. Taking all of this into consideration can greatly change target adherence rates from one drug to the next.

Additionally, different studies often define target adherence rates for the same drug or condition in different ways, making it even more difficult to manage adherence rates. In studies of hypertension and cardiovascular disease, for example, Chapman and colleagues used an 80% target adherence rate for patients based on pharmacy refill information, while George and Shalansky defined non-adherence as anything below 90%.

Likewise, Noens et al, measured adherence to inhibitor therapy in patients with chronic myeloid leukemia and found very little consistency in target adherence rates across studies. “We noted great heterogeneity in the definitions of adherence, including a lack of explanation about the use of the 80–90% cut off to distinguish across adherent and non-adherent patients with CML,” the authors wrote.

Since there’s no standard adherence rate for drugs, it’s important for marketers to do the research to figure out what their drug’s target adherence rate should be. Here are three examples of how different target rates can apply to different diseases and drugs.

HIV Target Adherence Rate: 95%

Due to the nature of HIV treatments, nearly perfect adherence is required to ensure viral suppression and restrict the development of a drug-resistant virus. Maintaining immune health and slowing progression of the disease can also be achieved through strict adherence to medications. Therefore, HIV patients who showed the most virological and immunological success maintained at least 95% adherence.

Chronic Myeloid Leukemia Target Adherence Rate: 90%

Chronic myeloid leukemia is a type of cancer that requires high levels of adherence in order to achieve a complete molecular response to treatment where the BCR-ABL gene is no longer found in the patient’s blood. A study by Jabbour et al, found that 44% of patients with rates of adherence at 90% or higher achieved this complete molecular response, while 0% of patients with adherence below 90% saw the same results. In this case, an adherence rate of 90% or above is imperative for better patient outcomes.

Diabetes Target Adherence Rate: Variable

Lo-Ciganic and colleagues found that adherence thresholds in patients with diabetes varied from person to person depending upon medication complexity and patient health. Thresholds were wide-ranging, between 46% and 94%, showing that the 80% standard adherence rate is not always the most predictive of positive outcomes.

“Our findings demonstrate that the 80% adherence threshold to oral hypoglycemics is not optimal for predicting risk of hospitalization among all patient subgroups,” the authors wrote. “Refill adherence thresholds for measuring quality of care may need to be customized by disease and patient complexity.”

While many of us still rely on 80% adherence as a standard, these examples show that target adherence rates are not always one-size-fits-all. Marketers need to dig a little deeper to find the target rate that is right for their application.