Methacholine challenge testing is superior to the exercise challenge for detecting asthma in children

Practical approaches to the diagnosis of asthma in school-age children

INTRODUCTION

Asthma is a chronic airways disease characterized by episodes of wheeze, chest tightness, and evidence of reversible airflow obstruction. Symptoms are frequently triggered by exercise, exposure to aeroallergens, and respiratory viruses. It is the commonest non-communicable respiratory condition in children, affecting over 5.5 million children in the European Union alone. Both over- and under- diagnosis of asthma are common for several reasons.

AREAS COVERED

The diagnosis is frequently based on parental or patient reported non-specific symptoms alone. All major asthma guidelines now recommend the use of objective tests, including spirometry, bronchodilator reversibility testing, fraction of exhaled nitric oxide measurements and challenge testing to confirm the diagnosis. Recently, the European Respiratory Society published the first evidence-based international guidelines for diagnosing asthma in school-age children using objective measures. Major barriers to implementation in primary care and less well-resourced healthcare settings are access to relevant objective tests for children and quality assurance to obtain reliable results.

EXPERT OPINION

We highlight the importance of diagnosing asthma in school-age children using objective tests and outline a practical approach for the use of widely available tests. We also review challenges and barriers to implementation of objective testing in children managed outside specialist settings.

European Respiratory Society clinical practice guidelines for the diagnosis of asthma in children aged 5-16 years

Diagnosing asthma in children represents an important clinical challenge. There is no single gold standard test to confirm the diagnosis. Consequently, both over-, and under-diagnosis of asthma are frequent in children.A Task Force (TF) supported by the European Respiratory Society has developed these evidence-based clinical practice guidelines for the diagnosis of asthma in children aged 5-16 years using nine PICO (Population, Intervention, Comparator and Outcome) questions. The TF conducted systematic literature searches for all PICO questions and screened the outputs from these, including relevant full text articles. All TF members approved the final decision for inclusion of research papers. The TF assessed the quality of the evidence using the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach.The TF then developed a diagnostic algorithm based on the critical appraisal of the PICO questions, preferences expressed by lay members and test availability. Proposed cut-offs were determined based on the best available evidence. The TF formulated recommendations using the GRADE Evidence to Decision framework.Based on the critical appraisal of the evidence and the Evidence to Decision Framework the TF recommends spirometry, bronchodilator reversibility testing and FeNO as first line diagnostic tests in children under investigation for asthma. The TF recommends against diagnosing asthma in children based on clinical history alone or following a single abnormal objective test. Finally, this guideline also proposes a set of research priorities to improve asthma diagnosis in children in the future.

Diagnosis of asthma in children: the contribution of a detailed history and test results

INTRODUCTION

There are few data on the usefulness of different tests to diagnose asthma in children.

AIM

We assessed the contribution of a detailed history and a variety of diagnostic tests for diagnosing asthma in children.

METHODS

We studied children aged 6-16 years referred consecutively for evaluation of suspected asthma to two pulmonary outpatient clinics. Symptoms were assessed by parental questionnaire. The clinical evaluation included skin-prick tests, measurement of exhaled nitric oxide fraction (F _eNO), spirometry, bronchodilator reversibility and bronchial provocation tests (BPT) by exercise, methacholine and mannitol. Asthma was diagnosed by the physicians at the end of the visit. We assessed diagnostic accuracy of symptoms and tests by calculating sensitivity, specificity, positive and negative predictive values and area under the curve (AUC).

RESULTS

Of the 111 participants, 80 (72%) were diagnosed with asthma. The combined sensitivity and specificity was highest for reported frequent wheeze (more than three attacks per year) (sensitivity 0.44, specificity 0.90), awakening due to wheeze (0.41, 0.90) and wheeze triggered by pollen (0.46, 0.83) or by pets (0.29, 0.99). Of the diagnostic tests, the AUC was highest for F _eNO measurement (0.80) and BPT by methacholine (0.81) or exercise (0.74), and lowest for forced expiratory volume in 1 s (FEV₁) (0.62) and FEV₁/forced vital capacity ratio (0.66), assessed by spirometry.

CONCLUSION

This study suggests that specific questions about triggers and severity of wheeze, measurement of F _eNO and BPT by methacholine or exercise contribute more to the diagnosis of asthma in school-aged children than spirometry, bronchodilator reversibility and skin-prick tests.

A Practical Approach to Severe Asthma in Children

Severe asthma accounts for only a small proportion of the children with asthma but a disproportionately high amount of resource utilization and morbidity. It is a heterogeneous entity and requires a step-wise, evidence-based approach to evaluation and management by pediatric subspecialists. The first step is to confirm the diagnosis by eliciting confirmatory history and objective evidence of asthma and excluding possible masquerading diagnoses. The next step is to differentiate difficult-to-treat asthma, asthma that can be controlled with appropriate management, from asthma that requires the highest level of therapy to maintain control or remains uncontrolled despite management optimization. Evaluation of difficult-to-treat asthma includes an assessment of medication delivery, the home environment, and, if possible, the school and other frequented locations, the psychosocial situation, and comorbid conditions. Once identified, aggressive management of issues related to poor adherence and drug delivery, remediation of environmental triggers, and treatment of comorbid conditions is necessary to characterize the degree of control that can be achieved with standard therapies. For the small proportion of patients whose disease remains poorly controlled with these interventions, the clinician may assess steroid responsiveness and determine the inflammatory pattern and eligibility for biologic therapies. Management of severe asthma refractory to traditional therapies involves considering the various biologic and other newly approved treatments as well as emerging therapies based on the individual patient characteristics.

[Guidelines for methacholine provocation testing]

Bronchial challenge with the direct bronchoconstrictor agent methacholine is commonly used for the diagnosis of asthma. The "Lung Function" thematic group of the French Pulmonology Society (SPLF) elaborated a series of guidelines for the performance and the interpretation of methacholine challenge testing, based on French clinical guideline methodology. Specifically, guidelines are provided with regard to the choice of judgment criteria, the management of deep inspirations, and the role of methacholine bronchial challenge in the care of asthma, exercise-induced asthma, and professional asthma.