Abstract
Microspirometry may be useful as the second stage of a screening pathway among patients reporting respiratory symptoms. We assessed sensitivity and specificity of the Vitalograph® lung monitor compared with post-bronchodilator confirmatory spirometry (ndd Easy on-PC) among primary care chronic obstructive pulmonary disease (COPD) patients within the Birmingham COPD cohort. We report a case–control analysis within 71 general practices in the UK. Eligible patients were aged ≥40 years who were either on a clinical COPD register or reported chronic respiratory symptoms on a questionnaire. Participants performed pre- and post-bronchodilator microspirometry, prior to confirmatory spirometry. Out of the 544 participants, COPD was confirmed in 337 according to post-bronchodilator confirmatory spirometry. Pre-bronchodilator, using the LLN as a cut-point, the lung monitor had a sensitivity of 50.5% (95% CI 45.0%, 55.9%) and a specificity of 99.0% (95% CI 96.6%, 99.9%) in our sample. Using a fixed ratio of FEV1/FEV6 < 0.7 to define obstruction in the lung monitor, sensitivity increased (58.8%; 95% CI 53.0, 63.8) while specificity was virtually identical (98.6%; 95% CI 95.8, 99.7). Within our sample, the optimal cut-point for the lung monitor was FEV1/FEV6 < 0.78, with sensitivity of 82.8% (95% CI 78.3%, 86.7%) and specificity of 85.0% (95% CI 79.4%, 89.6%). Test performance of the lung monitor was unaffected by bronchodilation. The lung monitor could be used in primary care without a bronchodilator using a simple ratio of FEV1/FEV6 as part of a screening pathway for COPD among patients reporting respiratory symptoms.
Highlights
Chronic obstructive pulmonary disease (COPD) is one of the most common long-term respiratory conditions with rising burden and mortality worldwide.[1,2,3] It is characterised by increasing breathlessness and decline in lung function, punctuated by episodes of acute exacerbations that often lead to hospital admission and result in poor prognosis and gradual deterioration of quality of life.[4]
We found that the lung monitor has high discriminatory accuracy among patients with existing chronic respiratory symptoms
We further demonstrated that using a bronchodilator with the lung monitor as part of screening offers no performance advantage
Summary
Chronic obstructive pulmonary disease (COPD) is one of the most common long-term respiratory conditions with rising burden and mortality worldwide.[1,2,3] It is characterised by increasing breathlessness and decline in lung function, punctuated by episodes of acute exacerbations that often lead to hospital admission and result in poor prognosis and gradual deterioration of quality of life.[4]. Screening programmes are not yet recommended, partly because of lack of evidence of the long-term benefits,[10,11] a view which is upheld in the most recent UK National Screening Committee report.[12] there are uncertainties around the performance of available screening tests, including symptom or risk assessment questionnaires and lung function-based measures, alone or in combination.[12,13] A recent study compared different screening strategies among current smokers, against post-bronchodilator spirometry This concluded that microspirometry or peak flow meters had the best performance, but interpretation was limited by a small sample size and low-quality spirometry data.[14] Microspirometers are small relatively inexpensive handheld devices that measure forced expiratory volume in 1 s (FEV1) and in 6 s (FEV6). Microspirometry can be undertaken in office settings and requires less time and patient effort.[15,16,17,18]
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