The current study found that the molecular diagnosis of IgE-sensitization to Hymenoptera venoms is valuable for the detection of culprit venom, especially in patients with dual or triple-sensitization. As the ALEX results demonstrated, mono- and double-sensitization to Hymenoptera venoms were observed in 22 and 6 patients, respectively. The most common Hymenoptera causing anaphylaxis were HB and YJ. Ves v 1 + /Ves v 5 + and Api m 1 + /Api m 2−/Api m 10− patterns were also identified as major sensitization patterns in these patients.

In our study, as well as the studies of Hirata et al., Seob Shin et al., and Bemanian et al., males were more frequent than females [18,19,20]. Gelincik et al. found that males and females had the same prevalence of Hymenoptera venom allergies in Istanbul [21]. This difference may be attributed to the culture effect such as the influence of wearing a hijab on women in some countries, and the higher frequency of men in difficult jobs such as agriculture, animal husbandry, and beekeeping. According to the Blank et al. study, being male could be considered a predictor of having positive IgE specific to HB [22]. Another study suggested that being male and older were risk factors for developing severe allergic reactions to Hymenoptera [23].

As the findings demonstrated, twelve patients (37.5%) reported a history of atopic diseases, most of which were allergic rhinitis (31.3%). This prevalence of allergic rhinitis is a little higher than in the general population (28.3%) [24]. In a study by Yavuz et al., bronchial asthma and allergic rhinitis were identified in 25% and 17.1% of children with Hymenoptera venom allergies, respectively [25]. As mentioned in the literature, atopic diseases could not be considered a predictor of developing hypersensitivity to Hymenoptera sting [21, 26]. Compared with individuals with mono-sensitization to Hymenoptera venom, an insignificantly higher prevalence of atopic diseases (28.8% vs. 42.1%) was observed in patients with dual-sensitization [27]. Although our study found a lower prevalence of atopic diseases in patients with dual or triple sensitization to Hymenoptera venom.

Ten (31.3%) patients reported a bite on the head and neck. The bite mainly affected the neck and upper limbs, although other limbs were involved as well. A study by Bemanian et al. reported that bites most frequently occurred in the upper limbs, followed by the head and neck [28]. The findings of the current study are consistent with those of previous studies regarding the major clinical manifestations [19, 25].

The lower sensitivity of SPT for Hymenoptera venoms leads to the use of the intradermal test to identify offending venom [29]. Based on our inclusion criteria and the intradermal test results, double and triple-sensitizated patients were included. Consequently, it is difficult to determine the genuine insect for allergen-specific immunotherapy. Using recombinant species-specific major molecules in Hymenoptera venoms and CCD inhibition may improve the ability to distinguish dual or triple sensitization from cross-reactivity [27].

In our study, 19 patients were identified with IgE sensitization to Apis mellifera components, of which 42.1% showed IgE-sensitization to more than one component, 57.9% to only one component, and 15.8% to all three components. In Kohler et al.’s study, IgE-sensitization to more than one molecule was 74.3%, while 9.7% showed positive specific IgE to all the studied allergenic molecules of Apis mellifera [30]. A 59.4% prevalence of IgE sensitization to at least one molecule of HB was found in the present study, while Kohler reported an 89.6% prevalence [30]. This difference could result from the difference in sample size and the number of allergenic molecules investigated between the two studies. As Bilo et al. stated, the evaluation of more allergic molecules increases the detection of the offending Hymenoptera [31]. According to our study, the most common sensitization pattern in HB-allergic patients was exclusive sensitization to Api m1 (Api m 1+/Api m 2−/Api m 10−) (25%). The next patterns were Api m 1+/Api m 2−/Api m 10+, Api m 1−/Api m 2−/Api m 10+ and Api m 1+/Api m 2+/Api m 10 + . In Kohler et al.’s study, these patterns were 11.81%, 3.47%, 4.17%, and 1.39%, respectively, although they also studied other molecules, including Api m 3, Api m 4 and Api m 5. Api m1+/Api m 2+/Api m 3+/Api m 4−/Api m 5+/Api m 10+ and Api m 1+ exclusive pattern was more common in the Kohler study [30].

Among 32 patients with positive intradermal reactions to Yellow Jacket Venom Protein extract, three showed positive specific IgE to whole extract from Vespula vulgaris in the ALEX test, so the intradermal test and whole extract of YJ in the ALEX test have poor agreement in this study. It could be due to the low amount of Ves v 1 and Ves v 5 molecules in the whole extract of YJ in the ALEX. Eikan et al. obtained an agreement of 79% between the skin tests and specific IgE assay [32]. The sensitivity of the specific IgE assay to the whole extract of YJ (Vespula spp.) was 83% using ImmunoCAP [33]. The differences between our study and other studies may be due to differences in measurement tools or the small sample size. On the other hand, different time intervals between the bite and the specific IgE assay can affect the results [34]. An evaluation of the allergenic components of Vespula vulgaris enabled us to identify seventeen patients while three of them were only positive in the whole extract in ALEX.

In the study of Strum et al., the molecular diagnosis was performed on 26 patients with allergy to YJ that showed no positive specific IgE to YJ whole extract. It's interesting that their study demonstrated positive specific IgE to rVes v 5 in 17 subjects (65.4%) [35]. In another study by Gawik et al., among 8 patients with negative sIgE to the whole extract of Vespula, 3 and 2 showed IgE sensitization to rVes v 5 and rVes v 1, respectively [36]. In our study, seven out of 29 patients with negative sIgE to the whole extract of Vespula vulgaris (Ves v) in ALEX had dual-sensitization to Ves v 5 and Ves v 1. Additionally, nine patients with a positive intradermal test for YJV showed a Ves v 5+/Ves v 1+ pattern. These variations may be explained by methodological or geographic differences as well as low levels of some molecules in the whole extract of YJ [37]. According to the Vos et al. study, ImmunoCAP showed positive sIgE to YJV whole extract in 83.4% of patients with allergy to YJ. Moreover, IgE sensitization to Ves v1 and Ves v 5 was identified in 44.2% and 89.9% of patients, respectively. Overall, 96.1% of patients were identified as the result of sIgE assays for Ves v 1 and Vesv5 [33]. In the same way, the present study identified 17 patients with sIgE to Ves v, Ves v 1 and Ves v 5.

In our study, the prevalence of Pol d 5 sensitization was 21.9% while Bilo et al. reported a prevalence of 69–72% [31]. This difference could be due to the geographic distribution of Hymenoptera and, of course, the sample size in our study. Furthermore, major allergen of Iranian patients may be different with other populations. In some studies, subjects with a positive skin test or sIgE to the whole extract were considered the baseline group. By contrast, our study included only patients who had positive skin tests. In Shin et al.’s study, there was a positive correlation between sIgE to the extract and the allergenic molecule of Pol d (r = 0.757) [19].

Molecular profiles and patient reports of Hymenoptera stings revealed that 15 patients had a history of stings along with IgE positive to allergenic molecules of the same reported insect. Despite a moderate agreement between the results of a specific IgE assay and the patients’ ability to identify offending insects [38], it could not alone help identify the causative insect. In the Reisman et al. study, among 46 patients with positive sIgE to bees, 26 individuals recognized the culprit Hymenoptera [38].

Although Api m 1 and Api m 2 seem to be associated with less severe anaphylactic reactions, there was no association between IgE sensitization to bee extracts and molecules and anaphylactic reaction severity. Gawlik et al. explored a positive correlation between specific IgE to Ves v 1, specific IgE to the whole extract of YJ and HB, and Api m1 with the severity of anaphylaxis [36].

As the findings of allergic sensitization to HB, YJ and PW extracts demonstrated, among 32 patients with dual or triple-sensitization in the intradermal test, 15 (46.9%), 1 (3.12%) and 2 (6.3%) patients showed exclusive sensitization to the whole extracts of Api m, Ves v, or Pol d, respectively, while 4 (12.6%) patients revealed positive specific IgE to two Hymenoptera. Following the molecular diagnosis with the ALEX test, 14 (43.8%) and 8 (25%) patients exclusively showed positive sensitization to Api m and Ves v components, and 9 subjects (28.1%) demonstrated allergic sensitization to allergenic components of two or three types of Hymenoptera (Table 2). In the study of Selb et al. 98 and 69 (70.4%) out of 255 patients showed dual-sensitization to allergen extract and allergenic molecules, respectively [39]. In our study, nine patients (30%) remained dual or triple-sensitized according to the ALEX test using both whole extract and components. This difference could be due to the evaluation of more molecules in the Selb et al. study [39]. Although, we should take note of the fact that all participants had positive allergic sensitization to the extracts in their study.

As the current study results demonstrated, a meaningful correlation was observed between sIgE to Api m and Api m 1 and Api m 10; Ves v and Ves v 5; and Pol d, and Pol d 5. Similarly, Hirata et al., study indicated the same result between Api m and its molecules, especially Api m 1 (r = 0.98) [20].

In light of the high cost of venom immunotherapy (VIT), especially for two or three venoms [40] and systemic anaphylactic reactions [41], the molecular diagnosis could help patients in reducing these issues. Using the intradermal test alone, patients would have to undergo VIT for at least two or three Hymenoptera, while the molecular diagnosis significantly decreases the number of VITs. Using ALEX, we observed mono- and double-sensitization to Hymenoptera venom in 22 and 6 patients, respectively. Moreover, this test meaningfully improved immunotherapy specificity towards related venom. Inhibiting cross-reactive carbohydrates in ALEX and identifying cross-reactive proteins could explain the differences between the two methods.

Since all cases of Polistes dominulus sensitization was associated with Vespula vulgaris sensitization, cross-reactivity is likely. Six patients showed positive specific IgE to Ves v 5 and Pol d 5. Ves v 5 is probably the cross-reactive component. The results are consistent with a Perez study that points out their high homology [8]. By identifying and evaluating genuine molecules of Polistes dominulus, true sensitization could occur.

We did face two limitations in our study, which were that some molecules, such as Api m 3 and Api m 5, were not evaluated and that the sample size was small. Expanding the repertoire of allergenic molecules could improve the effectiveness of this method for diagnosing Hymenoptera hypersensitivity.