Our meta-analysis result found that specific immunotherapy with standardized extract of aeroallergens in AD patient can significantly reduce the SCORAD. From the number of total populations included in our study, we are confident that our result represents the global population. Besides, studies that include also from various countries. In some studies, reduction of SCORAD will be seen after nine months of therapy using specific immunotherapy.(20) Another study showed that the specific immunotherapy treated group with AD saw a statistically significant improvement over the control group in SCORAD. Since the study by Pajno et al. of SLIT was in children, and Novak et al. of SCIT was in adults, it is difficult to make comparisons.(13,20,21) Some studies showed SCORAD in adults was more variate than children, which was due to population factor, ages, race, genetic, diet, and sample size.(22,23) Clinical manifestations can be calculated by the SCORAD but that is not always correlated with total IgE level.(24) A recent meta-analysis also showed a significant reduction in SCORAD, which our study included in the latest study.(25) SCORAD and Eczema Area and Severity Index (EASI) are some of the recommended results of the assessment signs for AD patients.(26)
We also investigated changes in the VAS score. VAS score for measured pruritus was the dominant symptom of AD patients.(27) Our study showed that VAS significantly reduced. Our meta-analysis was limited due to only two studies reporting this outcome and minimal population. But evidence from another study showed improvement in VAS.(28) The VAS score based on neurobiophysics and physiology was used to assess the patients’ subjective symptoms. This score can be a subjective evaluation reflecting the quality of life of the patient.(20) The first few studies reported symptomatic skin improvement after active therapy and significant improvement.(29,30) Irwanto et al. reported severity of AD was related with sleep problems, that could decrease the quality of life the patients, their cognitive function and behavioral patterns.(31) The decreased SCORAD and VAS values after the use of specific immunotherapy therapy are evidence of their efficacy in improving the quality of life for AD patients. The new study by Liu et al. showed significant decreased in DLQI of AD patients.(19) Previous study reported the positive correlation between the severity of AD in children evaluated with SCORAD which was assessed with IDQLI, and this study showed severity of AD can improve parents’ QOL which was assessed by FDLQI.(32–34)
The increase in IgG4 Dermatophagoides farinae was not significant in the findings of our meta-analysis. The data from Sanchez et al. and Qin et al. showed significant results whereas Novak et al. showed no significant results.(13,14,17) One study in this systematic review showed no significant difference in the decrease of specific IgE while another study reported significant difference in the decrease before and after treatment.(13,14) The study by Endaryanto et al. showed SLIT could decrease serum IgE, eosinophil count, and TH2 cytokines’ level.(35) The different results could be depending on the allergen concentration of the immunotherapy extract used.(36) In our review the findings were limited due to the heterogeneity and small study size, treatment protocols in types and doses of allergen, and duration of therapy. Some studies show an increase in IgG4 seen since the first month of therapy, while another study showed that after 70 days of specific immunotherapy therapy will increase specific IgA, IgG1, and IgG4 and the increase in IgG4 concentration from 10 to 100fold.(8,37,38) There is no guideline concerning sIgG4 as a biomarker to predict clinical effect of immunotherapy treatment.(39)
The increased sIgE and total IgE is one of the standards for a confirmatory diagnosis of allergy and are frequently elevated in AD.(40) In therapy with specific immunotherapy, there will be an increase in the initial few months followed by a decrease in sIgE after 6 to 12 months of therapy. Several studies have shown that long-term specific immunotherapy therapy for 2 to 3 years reduces sIgE.(41,42) Increases of IgG4 levels are associated with Interferon-gamma (IFN- γ), IL-10 and TGF- β.(43,44) In another study, the IgE/IgG4 ratio can be used as biomarkers for the efficacy of specific immunotherapy.(8) However, You et al. reported the serological biomarkers did not correlate with clinical improvement of AD patients.(45) Future trials could investigate the level of sIgG4 and sIgE at 2 or 3 years after specific immunotherapy, with larger sample size, same concentrations, to find the correlation with clinical responses.
Apart from sIgE and IgG4, several aspects that affect AD are age and race. One study showed that children with AD had lower levels of CLA + IFN-γ TH1 T cells than adults, whereas adults with AD had elevated IL-22.(46) In our meta-analysis, there was a wide distribution of age in the subject populations of the included studies, and accordingly it is possible that the immune responses could be different in the outcome. AD sufferers are also affected by race, and research showed that African-American children with AD have a 1.7-fold higher risk of those with European-American children, while Tackett et al. stated that people of color have a 3.37 higher risk of being moderate to severe AD, followed by the Latino race with 0.64 times and Caucasians with 0.6 times higher risk.(47,48)
One of genes that affects race is the FLG (Filaggrin) gene. FLG gene loss-of function mutations are the most widely studied genetic link to AD across ethnic groups, and some studies show it is mostly in European followed by Asian AD cases.(49) On histologic appearance, Asians with AD appear more psoriasiform, leading to increased epidermal hyperplasia and more parakeratosis. Psoriasiform dermatitis in Asian patients with AD is due to IL-9 and IL-22. The difference in appearance is because of the epidermal gene expression between Asians, Caucasians, and colored people.(50,51)
Local and systemic adverse events showed no significant differences with specific immunotherapy in our study. The reactions shown were dizziness, swelling of the mouth, face, itching of the lips, rhinitis, erythema, and some reactions will recover without treatment. The systemic reaction shown included flare-ups of eczematous, urticarial lesion, and asthma.(14,52) Cardona et al. reported the risk factor of systematic reaction was the age of patients under 20 years while another study found there was no fatality due to specific immunotherapy after more than 25 years of clinical use.(18,53)
Several limitations were noted in our study including heterogeneity of patients with eternal allergy, geographic variation in allergen exposure and differences in standards in doses.(54)