Of the 49 studies, 23 were for grass pollen, nine for trees, five for Parietaria, two for ragweed, eight for house dust mite, one for cat, and one for mixed allergens (birch and grass). Overall, SLIT led to a significant reduction in symptoms (SMD, -0.49; 95% CI, -0.64 to -0.34) and medication use (SMD, -0.32; 95% CI, -0.43 to -0.21). Sophisticated subgroup analyses were also included to reveal greater efficacy for house dust mite (perennial allergens) than other seasonal allergens, including grass. A trend toward a greater reduction in symptom scores was noted with a longer duration ( > 12 months) of SLIT.

Another meta-analysis, exclusively in the pediatric population, included 10 studies, of which four were for house dust mites, three for grass mixes, one each for Parietaria and olive, and one for pollen mix Kamagra online. Overall, a significant decline in both symptoms (SMD, 0.56; 95% CI, -1.01 to -0.10) and rescue medication use (SMD, 0.76; 95% CI, -1.46 to -0.06) was found. In concordance with the previous meta-analysis, subgroup analyses also found a greater efficacy when SLIT was used for a longer duration ( > 18 months). Interestingly, and in contrast, subgroup analyses with this meta-analysis suggested that SLIT administered for pollen was more efficacious than for house dust mites (Table 4).

Long-term clinical efficacy has been reaffirmed by Durham in a study of SLIT for grass pollen-induced allergic rhinoconjunctivitis. Sustained clinical improvement and immunomodulatory changes were noted at 1 year after treatment. There remains a relative paucity of data for SLIT in animal allergy, although the few available studies with cat extracts have shown potential efficacy. SLIT for AR also has the potential to mitigate the inception of new sensitizations as documented by Marogna et al,4³ showing an incidence of 3.1% in the SLIT-treated patients vs 34.8% (P = .01) in control subjects at a 3-year follow-up.

An important caveat to bear in mind with the various meta-analyses published for SCIT and SLIT is the significant heterogeneity with regard to patient population, allergen extracts used, and disease outcomes measured.

The presence of publication bias also introduces an element of statistical heterogeneity into these meta-analyses. These limitations suggest a cautious interpretation of results when extending to all patient populations, allergens, and AR vs asthma.

See Table 1 and 3 legends for expansion of other abbreviations. (Reproduced with permission from Calderon)

The complexity of using SIT and interpreting its efficacy is particularly evident with the concept of single vs multiallergen extract use. In the United States, allergists favor using multiallergen extracts, with the hope of addressing all major sensitivities, whereas allergists in Europe recommend against this practice Avanafil Canada, citing the rationale that inclusion of multiple allergens could potentially lead to a dilution effect, such that an effective dose is not given and also that proteolytic action of one extract on another might lead to its degradation.