Respiratory Assessment Instruments

Respiratory instruments answer two different questions. Control and impact questionnaires such as the Asthma Control Questionnaire, the Asthma Control Test, the Clinical COPD Questionnaire and the COPD Assessment Test ask how much the condition is affecting the person over a defined recall period, usually a week or four weeks. Breathlessness scales such as the Medical Research Council Dyspnea Scale, its modified version and the Borg CR10 Scale grade the symptom itself, either as a stable functional limitation or as an intensity rating at a moment in time.

Two further instruments sit here for specific reasons. The Leicester Cough Questionnaire measures cough-specific quality of life, which general respiratory questionnaires cover poorly. The Penetration-Aspiration Scale grades airway invasion during swallowing, which belongs here as much as with swallowing because aspiration is a respiratory risk.

The distinction between a control questionnaire and a breathlessness grade matters more than it looks. The Medical Research Council Dyspnea Scale grades a stable functional limitation and does not move quickly, so it is unsuitable as a short-term response measure. The Borg scale rates intensity at a moment and is used during exercise testing, so it is unsuitable as a description of usual state. Substituting one for the other produces either a flat line or unusable noise.

Recall period is the other recurring issue. The Asthma Control Questionnaire and the Asthma Control Test use different recall windows and different item sets, and their scores are not interchangeable even though both claim to measure asthma control. A study that changes instrument between phases has changed its endpoint.

Check the recall period and keep it fixed, and check whether the instrument includes a lung function item. Some versions of the Asthma Control Questionnaire include an FEV1 component and some do not, which means one version can be collected remotely and the other cannot.

Check licensing, which is unusually strict in this group. Several respiratory questionnaires are commercially licensed, require registration even for academic use, and control their translations separately.

Check that the instrument matches the condition. Asthma and COPD questionnaires are not interchangeable, and in populations with overlapping features the choice needs to be justified rather than assumed. Where breathlessness is the endpoint, state whether it is being measured as a stable limitation or as an intensity rating, because those are different endpoints with different analysis plans.

What is the difference between the MRC and modified MRC dyspnoea scales?

They use different grade numbering. The modified version runs from 0 to 4 and the original from 1 to 5, so a grade quoted without the version is ambiguous. State which version was used, and do not mix them within a dataset.

Can the Asthma Control Questionnaire be collected remotely?

The symptom-only versions can. Versions that include an FEV1 measurement require spirometry, so they need either a clinic visit or a validated home spirometer, and the version used must be reported.

Are the Asthma Control Questionnaire and Asthma Control Test interchangeable?

No. They have different items, different recall periods and different scoring directions. Choose one for a study and keep it for the duration.

Which instrument measures cough?

The Leicester Cough Questionnaire measures cough-specific quality of life. General respiratory questionnaires cover cough with one or two items at most, which is not enough when cough is the outcome of interest.