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Grass SLIT dependent on pollen exposure

The effects of grass sublingual immunotherapy tablets were dependent on pollen exposure in seasonal allergy trials, emphasizing the importance of interpreting individual trial results, recent data suggest.

“In this analysis, it is demonstrated that combined rhinoconjunctivitis symptoms and symptomatic medications use in grass-allergic subjects is closely associated with the level of grass pollen exposure,” Stephen R. Durham, MA, MD, FRCP, of allergy and clinical immunology at the Imperial College of London, and colleagues wrote.

The researchers examined the link between grass pollen counts and total combined rhinoconjunctivitis symptoms and medication scores (TCS) based on a post hoc analysis of data collected from six trials and seven grass pollen seasons in North America and Europe. Patients included those treated with sublingual immunotherapy tablets (SLIT, n=1,198) or placebo (n=1,165).

Data indicated that the magnitude of treatment effect dependent upon TCS was greater among those exposed to higher pollen (P<.001), the researchers wrote.

“The predicted percentage reduction in TCS = 12% + 0.35% × pollen count, implying that for each increase in average daily exposure of 10 grains/m3 during the first 20 days of the season, the relative difference in TCS is expected to increase by 3.5%,” researchers wrote.

In addition, corresponding correlations to the entire grass pollen season and to the peak season were equally good, the researchers wrote. There was a poor connection, however, between the difference in measured efficacy and pollen exposure during the last portion of the season.

“The dependency of the treatment effect on pollen exposure is an important relationship that must be considered when interpreting individual clinical trial results and comparing across trials and seasons,” the researchers concluded.

Disclosure: See the study for a full list of relevant financial disclosures.