Frequency and determinants of exaggerated bronchoconstriction during shortened methacholine challenge tests in epidemiological and clinical set-ups

Dose omission to shorten methacholine challenge testing: clinical consequences of the use of a 10% fall in FEV1 threshold

Introduction

In methacholine challenge testing (MCT), skipping a methacholine dose is suggested if FEV₁ falls by < 5%. Using a larger threshold may further shorten test duration, but data supporting this hypothesis is lacking. We evaluated the safety and consequences of using a 10% FEV₁ fall as threshold to skip the next dose of methacholine in patients undergoing MCT.

Methods

We reviewed MCTs performed in our center in 2017–2018. A ≤ 10% FEV₁ fall allowed the omission of the next methacholine dose. Patients of interest were those in which a dose was skipped after a previous FEV₁ fall outside the usual range (5–10%, termed “skip_5–10%”). Adverse events [AE; mild: > 1 nebulized salbutamol dose (2.5 mg) to reach basal FEV₁, palpitations; severe: hypoxemia and/or need for medical attention or intervention] were compared in the skip_5–10% group and others. Regression analysis was used to identify predictors of AE.

Results

208 MCTs were analysed (135 males, age 52 ± 15 years). Skip_5–10% occurred 111 times in 90 tests. Prevalence of AE was 5% and all were mild. Patients who developed AEs had lower FEV₁, FVC and FEV₁/FVC ratio, and higher lung volume values (all p < 0.05), but similar prevalence of skip_5–10% (36 vs. 44%, p = 0.64). Overall, MCTs in which at least one skip_5–10% occurred had a lower mean number of doses (3.1 ± 0.6 vs. 3.5 ± 1.3 doses, p = 0.007). Baseline residual volume was independently related to the development of AEs (OR 1.05, 95% CI 1.01–1.10, p = 0.01), but not the presence of a skip_5–10%, even when the skipped dose directly led to the reaching of PC₂₀ (OR 5.40, 95% CI 0.73–39.22, p = 0.10).

Conclusion

Omitting a methacholine dose based on a ≤ 10% fall in FEV₁ occurs frequently and has the potential to shorten test duration. AE are rare, but patients with worse baseline lung function and gas trapping are at increased risk of mild side effects.

Methacholine challenge testing: improved patient comfort with a 2-tiered protocol

BACKGROUND

The methacholine challenge test (MCT) is a test of bronchial hyperreactivity used as an aid in the diagnosis of asthma. MCT results are reported as the provocation concentration at which the forced expiratory volume in 1 second (FEV1) decreases 20% (PC20). The requirement for a 20% or greater decrease in FEV1 results in precipitous decreases in FEV1 in some patients.

OBJECTIVE

To improve MCT safety without compromising accuracy.

METHODS

We performed a retrospective analysis of 879 consecutive MCTs (derivation cohort). A novel protocol for MCT was developed and validated in a cohort of 564 MCTs performed in a second institution.

RESULTS

In comparison with a PC20 cutoff of less than 8 mg/mL, a provocation concentration at which the FEV1 decreases 10% (PC10) cutoff of 1 mg/mL or less has a sensitivity of 86%, a specificity of 98%, a positive predictive value (PPV) of 97%, and a negative predictive value (NPV) of 91%. We propose a novel 2-tiered protocol for MCT. If the PC10 is 1 mg/mL or less, bronchial hyperreactivity is present; if the PC10 is greater than 1 mg/mL, the test is continued until the provocative concentration is 8 mg/mL or a 20% decrease in FEV1 is achieved. Compared with the standard protocol, the proposed protocol has a sensitivity, specificity, PPV, NPV, and overall accuracy of 100%, 98%, 97.6%, 100%, and 99%, respectively. The modified protocol would have enabled us to avoid 26 of 42 cases (62%) in which a 40% or greater decrease in FEV1 occurred and would save 0.65 dose for every MCT performed. The 2-tiered protocol performed well in the validation cohort; sensitivity, specificity, PPV, NPV, and overall accuracy were 100%, 98%, 87%, 100%, and 98%, respectively.

CONCLUSION

The proposed 2-tiered protocol is accurate, saves time, and avoids precipitous decreases in FEV1.

Does the methacholine test reproduce symptoms?

BACKGROUND

The interpretation of methacholine test results do not usually consider the symptoms for which the subject was referred and those that occur during the test.

OBJECTIVE

To assess the association between methacholine test results and symptoms, and to examine variables that may affect this association.&nbsp;METHODS A total of 400 prospectively chosen subjects who underwent methacholine testing for possible asthma were investigated. The subjects answered a short questionnaire regarding the symptoms for which they had been referred and those that were encountered during the methacholine test.

RESULTS

The positive predictive value for the reproduction of symptoms during the test compared with symptoms for which subjects had been referred were 84% for dyspnea, 87% for cough, 81% for wheezing and 72% for chest tightness. The positive predictive value among the values obtained by measuring the provocative concentration of methacholine causing a 20% fall (PC20) in forced expiratory volume in 1 s on the one hand, and specific symptoms on the other, varied by up to approximately 50%; negative predictive values were higher. Forty-eight per cent of subjects with a PC20 of 16 mg⁄mL or lower reported that the test had globally reproduced their symptoms. This association was significantly stronger in women, young subjects and those taking inhaled steroids.

CONCLUSIONS

The methacholine test generally reproduced the symptoms for which the subjects were referred. The absence of a specific symptom (eg, dyspnea, cough, wheezing or chest tightness), either in daily life or at the time of methacholine testing, was more generally associated with a negative test than the reverse. The global impression that the test had reproduced what the patient had experienced in daily life was significantly associated with a positive test (ie, a PC20 of 16 mg⁄mL or lower), with the association being stronger in young subjects and women.

Matrix metalloproteinases, IL-8 and glutathione in the prognosis of workers exposed to chlorine

BACKGROUND

Workers exposed to chlorine may be at risk of deterioration in FEV1.

METHODS

A prospective study of 72 workers examined over a 5.8 +/- 1.9 year period. A sample of induced sputum for cells and mediators was obtained in 69 subjects at baseline (Vb) and in 36 both at Vb and at follow-up (Vf).

RESULTS

Sixty-four workers (89%) experienced at least one accidental inhalation of chlorine in the interval. The mean decrease in FEV1 was 30 ml/year and thus was within normal limits. Among the analysed remodelling markers, the level of the MMP-9-TIMP-1 complex, but not of free MMP-9 and TIMP-1, significantly diminished from Vb to Vf. We found significant correlations between neutrophils, IL-8, MMP-9 and MMP9-TIMP-1 complex at Vb and Vf. While levels of total glutathione, IL-8, MMP9, TIMP-1 and MMP9-TIMP-1 complex were highly correlated with each other at Vb, this was inconstant at Vf. Levels of MMP9-TIMP1 complex and of TIMP1 at Vf were significantly lower in workers reporting chlorine puffs with mild acute respiratory symptoms between visits compared to those who had no, or asymptomatic inhalations (P = 0.03 and 0.02, respectively). The fall in FEV1 from Vb to Vf was significantly correlated with levels of glutathione at Vb. Cough between visits was associated with a decrease in FEV1 (P = 0.06).

CONCLUSION

Although no accelerated loss in FEV1 was documented in these workers exposed to chlorine, subjects with a greater fall in FEV1 were more likely to report cough and have higher levels of total glutathione at Vb.

Long-term outcomes in a prospective cohort of apprentices exposed to high-molecular-weight agents

RATIONALE

We conducted a long-term (8-yr) follow-up of 408 apprentices entering programs involving exposure to high-molecular-weight allergens.

OBJECTIVES

The objectives were to assess the frequency of new and persisting sensitization, symptoms, and bronchial hyperresponsiveness in relation with job history after ending apprenticeship and to examine characteristics significantly associated with the incidence and remission of these occupational outcomes.

METHODS

A respiratory symptom questionnaire, skin prick tests with work-related allergens (laboratory animals, flour, and latex), spirometry, and methacholine challenge were administered. The association between incidence or remission of these outcomes and individual characteristics at baseline and end of apprenticeship was examined.

MEASUREMENTS AND MAIN RESULTS

In subjects who at any time during follow-up held a job related to their training (78%), the incidence of sensitization, rhinoconjunctival and chest symptoms, and bronchial hyperresponsiveness at follow-up was 1.3, 1.7, 0.7, and 2.0 per 100 person-years, respectively. The remission of these outcomes acquired during apprenticeship was 18.5, 9.6, 9.6, and 12.4 per 100 person-years, respectively, in subjects no longer in a job related to training. Several clinical, immunological, and functional characteristics at baseline and acquired during apprenticeship were found to be significantly associated with the incidence and remission of the outcomes.

CONCLUSIONS

The incidence of sensitization, symptoms, and bronchial hyperresponsiveness was lower while at work than during the apprenticeship period. A high proportion of subjects in a job not related to training experienced remission of symptoms acquired during apprenticeship.

[Bronchial hyperresponsiveness to methacholine assessed by means of tracheal auscultation of healthy children aged under 4 years]

OBJECTIVE

To assess the safety of the tracheal auscultation method for measuring bronchial hyperresponsiveness in healthy unsedated children aged less than 4 years and to establish a range of normal bronchial hyperresponsiveness values.

POPULATION AND METHODS

The study population consisted of healthy children aged between 6 months and 4 years. A methacholine bronchial provocation test was administered to unsedated children, using the tidal volume breathing technique and applying an abbreviated protocol. The test was considered positive when wheezing was heard in the trachea, arterial oxygen saturation (SaO2) fell by 5% or more, or respiratory rate increased by 50% or more.

RESULTS

A total of 16 children were studied. Ages ranged from 8 to 47 months, with a mean (SD) of 23.5 (12.2) months. There was no response to the methacholine in 11 children. In the other 5 children, there was a positive response at a concentration of 8 mg/mL. Response to the test was considered positive on the basis of tracheal wheezing in 3 cases, tracheal wheezing and a fall in SaO2 in 1 case, and a fall of SaO2 of 5% or more in 1 case. SaO2 never fell below 93%.

CONCLUSIONS

As a means for assessing bronchial hyperresponsiveness, the tracheal auscultation method is appropriate, is simple to apply, and can be safely administered to unsedated children aged less than 4 years. The lowest concentration at which a response to methacholine occurs in healthy children of this age group is 8 mg/mL.

Airway hyperresponsiveness and risk of chest symptoms in an occupational model

BACKGROUND

The clinical outcome of asymptomatic airway hyperresponsiveness (AHR) remains unclear. A study was undertaken to evaluate the incidence of respiratory symptoms in a cohort of asymptomatic subjects with AHR at baseline.

METHODS

A 3 year prospective study involving methacholine challenge tests and serially administered questionnaires was undertaken in 769 apprentices exposed to high molecular weight allergens. Analyses were performed on 428 initially asymptomatic subjects.

RESULTS

Thirty eight subjects (8.9%) were airway hyperresponsive (PC(20) < or =8 mg/ml) and asymptomatic at the start of the study. Forty four apprentices (10.3%) developed two or more respiratory symptoms unrelated to work, 13 (34.2%) in the AHR group and 31 (7.9%) in the non-AHR group (risk ratio (RR) 7.88 (95% CI 2.53 to 24.55) among subjects with AHR). The RR of developing two or more respiratory symptoms increased as the degree of PC(20) decreased with a significant trend (p<0.001). In a multivariate analysis, AHR (RR 8.33, 95% CI 2.65 to 26.16) and self-reported rhinitis on exposure to pollen through an interaction with a family history of asthma (RR 6.3, 95% CI 1.29 to 31.89) were associated with the incidence of two or more respiratory symptoms; atopy was not a significant covariate.

CONCLUSION

AHR in asymptomatic subjects is an important determinant for the development of respiratory symptoms outside the workplace among apprentices exposed to high molecular weight allergens in their training environment.

Methacholine challenge testing: comparison of the two American Thoracic Society-recommended methods

STUDY OBJECTIVES

Recent American Thoracic Society guidelines recommend two different methods of methacholine challenge testing: the 2-min tidal breathing method with twofold increases in concentration, and the five-breath dosimeter method with fourfold increases. Since the tidal breathing method delivers more methacholine to the mouthpiece, we hypothesized that the provocative concentration of methacholine required to decrease FEV(1) by 20% (PC(20)) would be lower than with the dosimeter method.

DESIGN

Twelve subjects 18 to 45 years old with stable asthma were selected on the basis of a screening PC(20) (by tidal breathing) of < 1 mg/mL, 1 to 4 mg/mL, or 4 to 16 mg/mL (4 subjects in each concentration range). On subsequent visits within a 7-day period, methacholine challenge testing with tidal breathing or dosimeter were performed on separate days, in a randomized crossover manner.

RESULTS

The geometric mean PC(20) was 1.8 mg/mL (95% confidence interval [CI], 0.7 to 4.3) after tidal breathing and 1.6 mg/mL (95% CI, 0.7 to 3.7) after dosimeter (p = 0.2). There was no significant difference between the screening PC(20) and the PC(20) obtained by either method on randomized study days. The maximum decrease in FEV(1) from diluent baseline after the last concentration was 27.8% (range, 20 to 50%) during tidal breathing and 27.9% (range, 16 to 47%) during the dosimeter method (p = 0.35).

CONCLUSIONS

Both methods give similar results. Fourfold increases in methacholine concentration with the dosimeter method are as safe as twofold increases with the tidal breathing method.

Incidence of occupational rhinoconjunctivitis and risk factors in animal-health apprentices

BACKGROUND

Exposure to laboratory animals often causes the appearance of immunologic sensitization and symptoms.

OBJECTIVE

Our aim was to determine the incidence of occupational rhinoconjunctivitis and the timing of symptoms and their determinants in apprentices starting exposure to laboratory animals.

METHODS

Data from 387 (92.8%) of 417 students entering career programs in animal health in 5 schools were kept for analysis. Questionnaires and skin prick tests with common and occupational inhalants were carried out on entry and at follow-up visits scheduled at 8, 20, 32, and 44 months, depending on the schools. Responsiveness to inhaled methacholine was assessed at entry.

RESULTS

Ninety-three (24%) subjects showed incident occupational rhinoconjunctivitis symptoms, and 37 (9.6%) had symptoms combined with skin sensitization to an animal-derived allergen. Symptoms such as sneezing, rhinorrhea, and itchy eyes tended to develop early in the course of exposure. In two thirds of the subjects, symptoms persisted at subsequent visits. In a multivariate analysis the determinants of the appearance of rhinoconjunctivitis with or without allergic sensitization included sensitization to grass pollens (odds ratio [OR], 1.78; 95% CI, 0.99-3.19), as well as nasal (rhinorrhea in contact with dust: OR, 1.79; 95% CI, 1.05-3.05) and bronchial symptoms (chest tightness: OR, 3.31; 95% CI, 0.98-11.25; cough on exposure to strong odors: OR, 1.88; 95% CI, 0.98-3.59).

CONCLUSION

The incidence of occupational rhinoconjunctivitis symptoms with or without immunologic sensitization is high in apprentices starting exposure to laboratory animals. Symptoms related to histamine release are common in the early course of exposure. Determinants include immunologic and target-organ susceptibility.

Rhinoconjunctivitis, bronchial responsiveness, and atopy as determinants for incident non-work-related asthma symptoms in apprentices exposed to high-molecular-weight allergens

OBJECTIVE

The aim of this study was to explore the role of rhinoconjunctivitis (RC), taking into account atopy and the level of bronchial responsiveness to methacholine, on the incidence of respiratory symptoms and in the development and/or worsening of asthma.

METHODS

We examined data from a prospective study in 769 students starting exposure to high-molecular-weight occupational allergens and who were serially followed for up to 44 months.

RESULTS

The presence of RC symptoms at baseline was significantly associated with an increased risk of developing shortness of breath and wheezing in atopic subjects regardless of PC20 level and in subjects with a PC20 <or= 32 mg/ml regardless of atopic status. RC symptoms were significantly associated with the development of exercise-induced respiratory symptoms. Multivariate analyses indicated that having a measurable PC20 was significantly associated with the incidence of all respiratory symptoms studied, whereas baseline seasonal RC was associated only with incident exercise-induced respiratory symptoms; atopy played a minimal role, and only through an interaction with seasonal RC.

CONCLUSION

Of the three potential factors for the development of respiratory symptoms that we considered, i.e. RC symptoms, having a measurable PC20 and atopy, having a measurable PC20 is the most significant one.

Incidence and host determinants of work-related rhinoconjunctivitis in apprentice pastry-makers

BACKGROUND

The authors recently assessed the incidence and determinants of immunologic sensitization to flour in apprentice pastry-makers. The aim of this work was to determine the incidence of work-related rhinoconjunctivitis (RC) symptoms and their determinants.

METHODS

For this 188/230 entrants (81.7%) were evaluated before starting exposure to flour, and again 10.8 and 16.8 months after. Questionnaires and skin prick testing to common and work-related allergens were administered at each visit. Bronchial responsiveness to methacholine was assessed at baseline in all subjects and in a subgroup at follow-up.

RESULTS

Thirty subjects (16.1%) reported new work-related RC symptoms (13.1 per 100 person-years); in three subjects (1.6%), these were accompanied by incident skin prick test reactivity to flour-derived allergens. Skin prick test reactivity to grass pollens (OR = 3.0, 95% CI, 1.3-6.7) and to pets (OR = 2.5, 95% CI, 1.1-5.9), persistent rhinitis (OR = 3.1, 95% CI, 1.1-8.4), seasonal RC (OR = 2.5, 95% CI, 1.1-5.5), RC on contact with pets (OR = 2.3, 95% CI, 1.03-5.0) and skin prick test reactivity to wheat flour (OR = 10.5, 95% CI, 2.3-46.8), assessed at baseline, were significantly associated with the incidence of work-related RC symptoms. Multivariate logistic regression analysis yielded significant OR of skin prick test reactivity to wheat flour at baseline (OR = 7.1, 95% CI, 1.7-35.1) and persistent rhinitis (OR = 3.9, 95% CI, 1.01-9.6) for the incidence of work-related RC symptoms. Increased bronchial hyperresponsiveness at follow-up was more frequent, although not significantly, in subjects positive to skin prick test to flour on entry and reporting new work-related symptoms (3/5), than in other subjects (4/17).

CONCLUSIONS

The incidence of work-related RC symptoms among apprentice pastry-makers was high (16.1% 30/186), while a minority (3/30) also developed skin prick test reactivity to flour. Skin prick test reactivity to wheat flour and persistent allergic rhinitis on starting exposure to flour are significant determinants for the development of work-related RC symptoms.

Utilization of pulmonary function measurements in the assessment of occupational asthma

Lung function assessments that include spirometry and bronchial responsiveness are now often coupled to immunological assessment and an evaluation of inflammation in the investigation of occupational asthma. For diagnostic purposes, evidence points out that specific inhalation challenges are the gold standard, as previously suspected. In the epidemiological setting, both spirometry and bronchial responsiveness are feasible and safe. The role of lung function assessments in surveillance programmes is still open to discussion.

Methacholine challenge: test-shortening procedures

STUDY OBJECTIVES

Validation of test-shortening procedures for the 2-min tidal breathing methacholine challenge method.

DESIGN

Retrospective chart review.

SETTING

Tertiary-care university clinical pulmonary function laboratory.

PATIENTS

One thousand subjects aged 10 to 85 years (mean +/- SD, 44.5 +/- 16.0 years), 44.5% male, referred for methacholine challenge.

INTERVENTION

Two-minute tidal breathing methacholine challenge was performed, with both physician and technician access to published test-shortening procedures.

MEASUREMENTS AND RESULTS

There were 315 positive test results (provocative concentration of methacholine causing a 20% fall in FEV(1) [PC(20)] < or = 8 mg/mL) and 685 negative test results. The subjects with positive test results were less likely to be male (39.1 vs 47.5%; p < 0.02) and had lower FEV(1) (91.8 +/- 14.9% predicted vs 97.2 +/- 13.9% predicted; p < 0.001). The average starting PC(20) was between 0.5 mg/mL and 1.0 mg/mL; the most common PC(20) was 1 mg/mL (67%). There were 431 skipped concentrations in 380 subjects. The mean number of methacholine inhalations was 3.7 +/- 1.1 (3.9 +/- 0.1 for negative test results vs 3.3 +/- 1.2 for positive test results; p < 0.001). Eighteen subjects had a > or = 20% FEV(1) fall on the first inhalation, and 11 subjects had a > or = 20% FEV(1) fall after a skipped concentration. In only one case (0.1%) an FEV(1) fall > or = 40% on the first concentration was reported, compared with no cases after a skipped concentration and seven cases with a > or = 40% FEV(1) fall after a routine doubling dose step-up.

CONCLUSIONS

The 2-min tidal breathing methacholine test in clinical practice can be safely shortened to an average of less than four inhalations using starting concentrations based on FEV(1), asthma medication, and clinical features, and by occasionally omitting concentrations.

Natural history of sensitization, symptoms and occupational diseases in apprentices exposed to laboratory animals

The natural history of the development of sensitization and disease due to high-molecular-weight allergens is not well characterized. This study describes the time-course of the incidence of work-related symptoms, skin reactivity and occupational rhinoconjunctivitis (RC) and asthma (OA); and assesses the predictive value of skin testing and RC symptoms in apprentices exposed to laboratory animals, in a 3-4-yr programme. Four-hundred and seventeen apprentices at five institutions were assessed prospectively with questionnaire, skin-testing with animal-derived allergens, spirometry and airway responsiveness (n=373). Depending on the school, students were seen 8 (n=136), 20 (n=345), 32 (n=355) and 44 (n=98) months after starting the programme. At all visits, the incidence was greater for work-related RC symptoms followed in order by skin reactivity, occupational RC, and, almost equally, OA and work-related respiratory symptoms. The incidence-density figures were comparable for each follow-up period and for most indices up to 32 months after entry into the study and then tended to decrease. The positive predictive values (PPVs) of skin reactivity to work-related allergens for the development of work-related RC and respiratory symptoms were 30% and 9.0%, respectively, while the PPVs of work-related RC for the development of OA was 11.4%. Sensitization, symptoms and diseases occur maximally in the first 2-3 yrs after starting exposure to laboratory animals. Skin reactivity to work-related allergens and rhinoconjuctivitis symptoms have low positive predictive values.

Incidence and host determinants of probable occupational asthma in apprentices exposed to laboratory animals

Laboratory animal (LA) workers are frequently affected with allergic sensitization and occupational asthma (OA). The role of preexposure host factors, in particular airway responsiveness, on the incidence of OA has not been satisfactorily studied. A prospective cohort study of 417 apprentices in animal-health technology was conducted to investigate the incidence and determinants of probable OA. Questionnaire and skin-prick tests with common and work-specific allergens were administered on entry and at follow-up visits (up to three) from 8 to 44 mo after starting apprenticeship. Responsiveness to inhaled methacholine was assessed at baseline and at follow-up in apprentices who developed a new specific skin sensitization and in control subjects. Preexposure host characteristics and the school attended were compared between cases and all cohort subjects not meeting the criteria for probable OA. Twenty-eight apprentices satisfied the definition for probable OA, i.e., onset of immediate skin reactivity to > 1 occupational inhalant and > 3.2-fold decrease in the provocative concentration causing a 20% reduction in FEV(1) (PC(20)). The incidence of probable OA was 2.7% (28/1,043 person-years). Baseline immediate skin reactivity to pets (rate ratio [RR] 4.1, 95% confidence interval [CI] = 1.6 to 10.8), and bronchial responsiveness (PC(20) < or = 32 versus PC(20) > 32 mg/ ml) (RR = 2.5, 95% CI = 1.0 to 5.8) were associated with an increased risk of probable OA; a lower FEV(1) had an apparent, protective effect (RR = 0.58, 95% CI = 0.43 to 0.78). It is concluded that apprentices in animal health show a high incidence of probable OA, and that preexposure airway caliber and responsiveness as well as sensitization to pets are associated with an increased risk.