Immunotherapy Compliance: Dutch Study Shows Weaknesses

By Dr. Larry Chiaramonte

Compliance is my beat.  While I usually discuss the shortcomings of asthmatic patients keeping up with their prescribed doses of inhaled corticosteroids (ICS) or combinations of ICS and long-acting beta agonists, the issue of medication fatigue is a factor for other treatments, too.  A new study from the Netherlands shows us how patients do with the recommended three-year term of immunotherapy for environmental allergies, whether given in the form of allergy shots (sub-cutaneous immunotherapy, or SCIT) or drops under the tongue (sub-lingual immunotherapy, or SLIT).

The researchers analyzed community pharmacy data for 6486 patients who started immunotherapy for one or more of grass pollen, tree pollen, and dust mites between 1994 and 2009. Two thousand seven hundred ninety-six patients received SCIT, and 3690 received SLIT. They found:

“Overall, only 18% of users reached the minimally required duration of treatment of 3 years (SCIT, 23%; SLIT, 7%). Median durations for SCIT and SLIT users were 1.7 and 0.6 years, respectively (P < .001).”

The fact that compliance is substantially lower with SLIT than SCIT in this study comes as a surprise. From my extensive study of the literature and very limited hands on experience, however, I can see a possible explanation. While in general SLIT seems to have fewer serious systemic reactions, there is a high incidence of minor but annoying reactions. The annoying reactions can affect compliance. The varying dosages used in SLIT may play a role in this.

Drilling deeper into the Dutch data revealed some further surprises. For one thing, those who received their prescriptions from general practitioners were more persistent than those who got them from allergists; maybe those allergists should work on their bedside manner. Other predictors of premature discontinuation were whether they were being treated for a single-allergen, lower socioeconomic status, and younger age.

As an American allergist, I find this data intriguing for a number of reasons. For one thing, it shows that a country where the health care system is often rated the best in Europe is probably no better at getting patients to do what’s good for them than we are. For another thing, the data on SCIT vs. SLIT runs contrary to the conventional wisdom. While completion rates for both were lousy, SLIT—the painless one–was much worse.

SLIT is widely used in Europe, while in the United States it hasn’t been approved for general use. American studies show that SLIT is less effective than SCIT. You would think that ease of use and lack of needle-phobia should even out the differences in the way a once-a-day pill for asthma becomes as effective as twice-a-day inhalers (see my last piece). But this study shows that this may not be the case after all. Patients give up the “easy” medication more readily than the “difficult” one.

Why should that be, apart from the annoyance factor? I’m not a behavioral psychologist so I can only guess. Maybe the taste is worse than the pain of the shot. Maybe the routine of going for a shot at regular intervals reinforces the idea of therapy, whereas the drops are too easy. Perhaps even a marginal difference in effectiveness is meaningful—patients do tend to be more compliant if they feel better, although when they feel well enough they also stop taking their medicine. All I do know is that anyone who thinks the work is done when efficacy has been proved without considering patient behavior over time is kidding himself. We know this about seasonal and environmental allergies. We know it about asthma. And if treatments for food allergies ever hit the mainstream, we can be sure that the same issues will apply. In the words of that eminent Italian-American philosopher, Lawrence Peter Berra, “It ain’t over till it’s over.”

“Windmills on Montmartre” by Vincent Van Gogh from wikipedia.org