Ragweed pollen focus predicts seasonal rhino-conjunctivitis and bronchial asthma severity in sufferers allergic to ragweed


Examine design

The first objective of this research was to research the affiliation between publicity to airborne ragweed pollen and each day ocular, nasal, and respiratory signs, similar to bronchial asthma, in two subgroups of sufferers all through the ragweed season. We monitored people sensitised to ragweed and affected by seasonal ragweed rhino-conjunctivitis with/with out bronchial asthma from 16 July to fifteen September 2014. Examine members had been divided into two teams: one consisting of people who had by no means acquired a ragweed AIT, subsequently named “no AIT”, whereas members within the different group had been handled with ragweed AIT, subsequently named “AIT handled”. The sufferers had been handled with AIT previous to and unbiased of their enrolment within the research. These sufferers acquired AIT therapy both in the identical 12 months because the research or within the three years instantly previous the research.

We initially envisioned a distinct research design. Ragweed and mugwort coexist within the research space, and since mugwort and ragweed blooms partly overlap, we first thought-about investigating the affect of mugwort publicity on allergy signs attributed to ragweed. Nevertheless, as a result of the variety of sufferers with twin sensitisation (that’s, ragweed and mugwort) was small (n = 25), the unique research design was modified to incorporate solely members sensitised to ragweed.

From 16 July 2014 to fifteen September 2014 all sufferers included within the research accomplished a each day medical diary of signs and medicines (CDSD). Throughout the identical interval, pollen counts had been measured from three pollen traps situated within the research space (see the ‘Pollen focus’ part for the precise areas). The each day averages of ragweed and mugwort pollen concentrations obtained from the three pollen traps had been used for statistical calculations in opposition to the each day imply symptom/drug scores for every of the 2 subgroups.


Sufferers had been recruited and monitored within the areas of the ASST Ovest Milanese and ASST Rhodense districts, each of that are below the Milanese Well being Safety Company ATS (Fig. 1). Each districts are situated within the North-West metropolitan space of Milan, masking an space of roughly 827 sq. km (geographical coordinates: to the East: Lat 8° 39′ 59′′ E, to the North: Lengthy 45° 35′ 54′′ E, to the West: Lat 9° 11′ 47′′ E, to the South: Lengthy 45° 16′ 46′′ N (with the exclusion of the municipality of Milan)). Sufferers inside the two districts had been enrolled within the allergy items of the next hospitals: Legnano Hospital (Lengthy 45° 35′ 44′′ N, Lat 8° 55′ 23′′ E), Abbiategrasso Hospital (Lengthy 45° 23′ 40′′ N, Lat 8° 54′ 49′′ E), Garbagnate Milanese Hospital, Pneumology and Pediatric allergy items (Lengthy 45° 34′ 53′′ N, Lat 9° 05′ 14′′ E), and Cesano Boscone Ambrosiana Clinic (Lengthy 45° 26′ 57′′ N, Lat 9° 05′ 33′′ E). Every of those 5 allergy items was situated in proximity to one of many three pollen traps (that’s, min–max distance: 0.2–19.6 km) (Fig. 1).


Members within the research had been a random pattern of residents residing within the designated space with a confirmed analysis of ragweed seasonal rhino-conjunctivitis (with or with out bronchial asthma), a few of whom had been handled with AIT. A complete of 66 members (32 males and 34 girls) had been enrolled within the research. The eligibility standards for participation within the research had been as follows: (1) the members had been sensitised to ragweed pollen, demonstrated by a constructive pores and skin prick assessments (SPT) with business ragweed extracts (Lofarma SpA, Milan; ALK-Abellò SpA, Milan) and immunoglobulin (Ig)Es for the full ragweed extract and for rAmb a 1 (pectate lyase) (ImmunoCAP Thermo Fisher Scientific Inc., Monza, Italy). Within the case of discordant check outcomes, ragweed sensitisation was confirmed primarily based on constructive IgE outcomes for rAmb a 1. (2) The members had a longtime and documented historical past of medical manifestations of ragweed allergy (that’s, signs of rhino-conjunctivitis, with or with out bronchial asthma), coinciding with the ragweed flowering interval, within the years instantly previous enrolment. (3) The members supplied knowledgeable consent. (4) Members had been in a position to adhere to the research protocol and (5) members remained of their residence all through the commentary interval.

All eligible research members carried out SPT with 12 different inhalant allergens, particularly pollens of grass, birch, hazel, alder, mugwort, Dermatophagoides pteronyssinus, Dermatophagoides farinae, Aspergillus, Cladosporium, Alternaria, cat and canine dandruff. Furthermore, blood particular IgEs (sIgEs) to mugwort allergen extract, rArt v 1 (recombinant defensin-like protein linked to the polyproline-rich area) and rArt v 3 (recombinant NS LTP sort 1) have been decided. Desk 1 experiences the degrees of particular IgEs (imply, ±, sd) to (1) ragweed extract, (2) mugwort extract and to separate recombinant molecular parts of ragweed and mugwort pollen. They’re (3) rAmb a 1, (4) r Artwork v 1 and (5) rArt v 3. The averages of particular IgE ranges for every allergen extract/part had been calculated by gender, age group and subgroup of AIT handled and no AIT handled people.

Desk 1 Particular IgE to ragweed and mugwort extracts, to Amb a 1, Artwork v 1, and Artwork v 3 parts of 66 members enrolled within the research.

A lot of the members handled with AIT had been sensitised to different pollen, along with ragweed, notably mugwort (that’s, 22 constructive). Sensitisation to mugwort could have affected the signs used to judge the effectiveness of AIT for ragweed as a result of the flowering of mugwort and ragweed overlapped within the space throughout the research interval (July–September). We hypothesize, nevertheless, that this affect, within the case of our research, was irrelevant as a result of the focus of mugwort pollen was extraordinarily low within the commentary interval (Figs. 3 and 4) and, furthermore, the typical of the IgE values particular for mugwort detected within the sufferers chosen for the research was low (that’s, Artwork v 1 = 1.1 ± 3.9 kUA/L and Artwork v 3 = 0.4 ± 1.8 kUA/L) (Desk 1). Sensitisation to different pollens that provoked pollen allergy in our space (that’s, timber and grasses) was irrelevant for the needs of the research as a result of the load of those pollens throughout the commentary interval was absent or irrelevant for the aim of frightening signs. The AIT was not a part of the admission/exclusion standards to permit the enrolled members to proceed the present or already deliberate AIT. The AIT, each in youngsters/adolescents and adults, was carried out with pre-seasonal or pre-co-seasonal modalities with a period of 8 weeks, repeating the therapy for 3 seasons. Throughout the commentary interval, the AIT members who had undergone the pre-seasonal process had completed therapy, whereas those that had undergone the pre-co-seasonal process had been in the midst of therapy. The imply values of sIgEs to ragweed extract and to Amb a 1 within the subgroups no AIT and AIT weren’t considerably completely different. It may be seen in Desk 1 that the extent of sIgE for ragweed will increase within the extra superior age teams. This phenomenon is simply obvious, the truth is the pattern of sufferers > 60 years consisted of solely 4 people of which one had very excessive values of sIgE to ragweed extract (> 100 kUA/L) and to Amb a 1 (> 100 kUA/L). This discrepancy may very well be inferred from very excessive s.d. proven in Desk1.

What’s extra, in accordance with Desk 1 sufferers with out AIT therapy all the time had sIgE ranges decrease than those that was prescribed with AIT. We didn’t decide the preliminary ragweed sIgE values previous to the beginning of the AIT and subsequently we can’t interpret the which means of the ultimate values. It should even be thought-about that the general period of AIT in our sufferers was restricted, the truth is they didn’t obtain a perennial AIT however a pre-seasonal or pre-co-seasonal AIT (restricted to 16 weeks/12 months after which suspended for 36 weeks). Consequently, the recognized enhance in particular IgE within the early phases of present AIT therapy might have influenced the typical sIgE ranges of the full inhabitants31. Apparently, a rise in particular IgE has just lately been noticed in sufferers with allergy to pollens (together with allergy to ragweed) regardless of just a few years of AIT upkeep with corresponding allergen extracts. The authors interpret this paradoxical enhance in sIgE on the premise of environmental modifications which may enhance the allergenic efficiency of main allergens in pollens similar to ragweed32.

To compensate for potential lacking information, three periodic examinations had been deliberate. Sufferers who didn’t precisely full the each day diary had been excluded from the evaluation.

On the finish of the recruitment interval, from 1 February 2014 to fifteen July 2014, 71 members had been assessed utilizing the eligibility standards. One participant was excluded as a result of he didn’t endure the IgE check, and 4 had been excluded as a result of the IgE for rAmb a 1 was destructive. The remaining 66 sufferers had been confirmed to be eligible and had been included within the research. The imply age was 36.5 years (vary: 8–69 years). Not one of the members had been pregnant or had persistent ailments. All members resided within the research space, and within the interval from 1 February 2014 to fifteen July 2014 that they had an allergic go to for respiratory signs in one of many 5 allergy items collaborating within the research. Furthermore, 42 members had by no means been handled with AIT for ragweed, whereas 24 members had beforehand acquired ragweed AIT. Thus, the sufferers had been divided into two subgroups: no AIT and AIT handled. All recruited members (100%) accomplished the follow-up and took part in statistical evaluation. The traits of the research cohort at enrolment are introduced in Desk 2.

Desk 2 Traits of the research base at enrolment.

Pollen focus information

Ragweed and mugwort pollen had been sampled each day utilizing three Hirst-type pollen traps situated in Legnano (45° 35′ 44″ N, Lengthy 8° 55′ 23″ E), Magenta (45° 28′ 16″ N, Lengthy 8° 53′ 33″ E), and Rho (45° 32′ 51″ N, Lengthy 9° 02′ 42″ E), respectively. The Hirst volumetric lure repeatedly attracts 10 L of air per minute onto adhesive-coated tape. Particles within the air keep on with the tape, which strikes at 2 mm/h to offer a each day pattern. The pollen collected from the traps was recognized and quantified by a specialised technician after which correlated to the typical air quantity over 24 h. The reference customary adopted for the sampling and counting of pollen was UNI 11108 of 2004, which was legitimate on the time of the research.

The next definitions had been adopted from the High quality Management Working Group of the European Society of Aerobiology (EAS) and Worldwide Affiliation of Aerobiology (IAA)33: Pollen depend: results of the slide evaluation; this amount isn’t comparable and have to be transformed into focus. Pollen grain: male gametophyte of seed vegetation. Pollen focus was expressed as pollen grains/m3, that’s, the variety of pollen grains dispersed within the air per unit of air quantity. Primary pollen season (MPS): the size of time that pollen is current within the environment at important concentrations in a spot. The MPS in our research was primarily based on the typical of the three monitoring stations utilizing the Nillson & Persson criterion34: “the interval from when the sum of the typical each day pollen concentrations reached 5% of the full sum as much as the time when the sum reached 95%, that’s, the primary pollen season with 90% of the complete amount of pollen collected”. For the aim of this research, we outlined the height pollen interval (PPP) because the interval of MPS with greater ragweed pollen concentrations, utilizing 25 pollen/m3 because the cut-off worth.

Medical diary of signs and medicines (CDSD)

All research members had been requested to finish the CDSD throughout the follow-up interval. Sufferers had been requested to report their each day signs and medicine use each night from 16 July to fifteen September 2014. Every symptom was rated on a 4-point scale: 0, no signs; 1, delicate signs; 2, reasonable signs; and three, extreme signs. These rankings had been used to attain every of the next 9 distinct signs: nasal, (1) nasal congestion/nasal respiratory problem and (2) runny nostril, (3) itchy nostril, (4) itchy throats/ears; ocular, (5) itching and/or burning eyes, (6) tearing and/or moist eyes; bronchial, (7) cough, (8) respiratory difficulties whereas transferring and (9) respiratory problem at relaxation. Due to this fact, the full symptom rating ranged from 0 to 24, the nasal rating ranged from 0 to 9, the ocular rating ranged from 0 to six, and the bronchial rating ranged from 0 to 9. Moreover, sufferers had been additionally requested to report each single unit of drug taken, that’s, the variety of tablets/day of oral antihistamines, variety of sprays/day of inhaled topical nasal corticosteroids, topical bronchial corticosteroids, topical bronchial corticosteroids, long-acting bronchodilator brokers (LABA) or short-acting bronchodilator brokers (SABA), and variety of drops/day of antihistamine eye drops.

Affected person follow-up throughout the publicity interval

All sufferers enrolled within the research visited their reference allergy unit instantly earlier than the publicity interval started. Throughout the go to, medical historical past was collected, a medical examination was carried out, and sufferers supplied knowledgeable consent for participation within the research. All sufferers had been additionally supplied with a CDSD, which was compiled for all dates throughout the second go to, after 15 September 2014.

Comparability of analysis strategies

Sufferers in each teams, those that weren’t handled with AIT and people who had been AIT handled, had been recruited for the research utilizing the identical technique, underwent the identical diagnostic assessments, acquired the identical CDSD, had been adopted up on the identical dates, and acquired the identical informative consent.


The recognized overlap within the preliminary time interval of ragweed MPS with mugwort MPS was a potential explanation for bias with respect to the symptom rating attributed to ragweed, as a result of the signs probably brought on by publicity to mugwort pollen had been indistinguishable from these brought on by ragweed pollen in members delicate to each pollen species. Nevertheless, the focus of mugwort pollen detected throughout the research interval was very low (see beneath) and subsequently, unlikely to have influenced in any important approach the respiratory signs of these sufferers additionally allergic to mugwort.

Different potential causes of bias on the symptom/drug rating could have been climatic variables, air air pollution, any intercurrent respiratory infectious ailments, and the management of signs by means of symptomatic medicines (which weren’t thought-about to simplify the analyses).


The research protocol complied with the Declaration of Helsinki and all subsequent amendments of Tokyo 1975, Venice 1983, and Hong Kong 1989, in addition to with the present rules for good medical apply (GCP). The protocol additionally complied with all nationwide and group rules relevant to observational research, and all moral and deontological ideas that encourage the medical career. This research was accredited by the Ethics Committee of Milan Space C (No. 80_122013).

Quantitative variables

Solely ragweed pollen focus was thought-about as a characteristic within the regression fashions as a result of the correlation between symptom/drug rating and mugwort pollen focus was general low and never important.

Statistical analyses

Spearman’s rank ρ correlation coefficient35 and Kendall’s rank τ correlation coefficient36 nonparametric statistical assessments had been used to look at the correlation between each day ragweed pollen concentrations and symptom depth, which was measured as the full each day variety of signs noticed within the research members. We adopted a nonparametric statistical strategy as a result of the goal variables weren’t usually distributed.

The nonparametric Kruskal–Wallis check37 and the Wilcoxon rank sum check38 had been used to check imply symptom degree scores between the 2 teams of sufferers: the group handled with AIT and the group not handled with AIT.

Time-series evaluation was used to analyse the affect of the each day pollen focus cycle on the onset of allergic signs. It’s cheap to imagine that the full variety of signs at present noticed is determined by the each day pollen concentrations, in addition to on the symptom values of the day prior to this (lag = 1) symptom values. Due to this fact, we utilized a first-order autoregressive distributed lag (ARDL) mannequin to discover these short-run relationships39.

({x}_{t})(t = 1, …,T) represents the each day pollen concentrations and ({y}_{t}) the full variety of signs noticed within the research sufferers. The ARDL mannequin is outlined as follows:

$$y_{t} = alpha + phi_{1} y_{t – 1} + theta_{0} x_{t} + varepsilon_{t} ,;;left( {{textual content{t}} = {1}, ldots ,{textual content{T}}} proper)$$


the place εt is a white noise course of, unbiased of (x_{t}), (y_{t}) and (y_{t – 1}), in order that the mannequin (1) could be estimated utilizing peculiar least squares (OLS). The regression coefficients could be interpreted as measures of the affect of the characteristic on the goal variable.

We additionally thought-about a first-order autoregressive distributed lag mannequin much like the mannequin formulated in (1), with the addition of a lagged (x_{t – 1}) as an extra explanatory variable:

$$y_{t} = alpha + phi_{1} y_{t – 1} + theta_{0} x_{t} + theta_{1} x_{t – 1} + varepsilon_{t} ,;;left( {{textual content{t}} = {1}, ldots ,{textual content{T}}} proper)$$


The Akaike data criterion (AIC) and Bayesian data criterion (BIC) had been used for mannequin choice. The fashions with the bottom AIC and BIC values had been thought-about optimum. Lastly, as a result of the pollen focus information confirmed excessive variance, we used a sq. root transformation to stabilise the variance.

All statistical analyses had been carried out utilizing R 4.0.2 software program40.

Ethics approval

All of the procedures carried out on this research involving human members had been in accordance with the moral requirements of the nationwide analysis committee and with the moral requirements as laid down within the 1964 Declaration of Helsinki and its later amendments or comparable moral requirements. The authors affirm that the research was accredited by the Bioethics Committee Milano Space C (No 80_122013).

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