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

Area of Science:

• Pulmonary Medicine
• Diagnostic Testing
• Respiratory Physiology

Background:

• The methacholine challenge test (MCT) assesses bronchial hyperreactivity for asthma diagnosis.
• Current MCT protocols report results based on a 20% decrease in forced expiratory volume in 1 second (FEV1), which can lead to precipitous FEV1 drops in some patients.

Purpose of the Study:

• To enhance the safety of the methacholine challenge test (MCT) without compromising its diagnostic accuracy.
• To develop and validate a novel, safer protocol for bronchial hyperreactivity testing.

Main Methods:

• Retrospective analysis of 879 methacholine challenge tests (MCTs) to derive a new protocol.
• Validation of the novel two-tiered MCT protocol in a separate cohort of 564 MCTs.
• Comparison of the proposed protocol's performance against the standard protocol using sensitivity, specificity, PPV, and NPV.

Main Results:

• A two-tiered protocol using a 10% decrease in FEV1 (PC10) cutoff of 1 mg/mL or less demonstrated high diagnostic accuracy (Sensitivity: 86%, Specificity: 98%).
• The proposed two-tiered protocol achieved 100% sensitivity, 98% specificity, and 99% overall accuracy in the derivation cohort.
• The modified protocol successfully avoided 62% of cases with precipitous FEV1 decreases (≥40%) and reduced medication dosage by 0.65 per test.
• Validation in a second cohort confirmed the protocol's high performance (Sensitivity: 100%, Specificity: 98%, Overall Accuracy: 98%).

Conclusions:

• The novel two-tiered methacholine challenge test protocol is accurate and safer than the standard method.
• This protocol effectively avoids precipitous forced expiratory volume in 1 second (FEV1) decreases.
• The modified protocol offers time savings and improved patient safety in diagnosing asthma.