Adherence Does NOT Require 100% Compliance

(Green and red medicine bottle image from Google Gemini)

As many of you know, I spend the majority of my time in identity/biometrics, where in some cases a 99% accuracy rate is considered woefully inadequate. Imagine if your bank had a million customers and 10,000 of them couldn’t login…or 10,000 fraudsters COULD log in. The bank would throw a fit with its biometric vendor.

So perhaps my experience resulted in…um, bias when I wrote the following in my recent post on adherence and identity:

“Let’s say you are told to take 4 pills a day for 7 days, and the pharmacy gives you a prescription for 28 pills. A week later all the pills are gone.

“Does this demonstrate patient adherence to health instructions?”

Perhaps you spotted the implicit assumption that taking 28 of 28 pills (100%} constitutes adherence, while taking 27 of 28 pills (96.4%} constitutes NON-adherence.

Tain’t so, Sherlock, as Philip Morisky pointed out in a comment on my LinkedIn post on adherence and identity. He said, in part:

“…the threshold at 80% means that even if you do not have access to the medication for 6 out of 30 days, you are still considered adherent.”

Morisky presumably knows what he’s talking about, since he works for a company called…adherence. And Philip’s father, Dr. Donald Morisky, developed the Morisky Medication Adherence Scale (MMAS) for medication self-reporting.

But what of this 80% threshold? 

It’s commonly cited…like the statement that 30% of crime scene latent prints come from palms. 

But the 80% adherence threshold is not universally accepted, as this National Library of Medicine study notes.

“Based on Haynes’s early empirical definition of sufficient adherence to antihypertensive medications as taking ≥80% of medication, many researchers used this threshold to distinguish adherent from non-adherent patients. However, we propose that different diseases, medications and patient’s characteristics influence the cut-off point of the adherence rate above which the clinical outcome is satisfactory (thereafter medication adherence threshold).”

This particular study concluded that…more research is needed.

“…we cannot reject or confirm the validity of the historical 80% threshold. Nevertheless, the 80% threshold was clearly questioned as a general standard.”

Despite the questions about the 80% threshold, Philip Morisky’s basic point remains: you don’t have to take 100% of your medications to be considered adherent from a health perspective.

But I still maintain that for critically important medications, the IDENTITY of the person taking them needs to be known at a level very close to 100%.