Abstract
Introduction:
Diagnostic confusion between COPD and asthma abounds in clinical practice and epidemiological surveys, as symptoms are non-specific. Spirometry is essential for the diagnosis of COPD, but is neither widely used nor reliably performed in general practice. The DDQ was developed to help GPs differentiate patients with respiratory symptoms into the category ‘likely COPD’.
Aims and objectives:
To validate the DDQ prospectively in Australian primary care. Subjects and
Methods:
Forty-two GPs in Adelaide, Brisbane and Sydney recruited patients aged >40 years with a previous diagnosis of asthma or COPD, or with recent respiratory medication prescription. Diagnostic validity — DDQ scores were compared to spirometry in 131 patients, using two pre-determined cutpoint scores: 24.5=‘high likelihood’ (HL) and 18.5 = ‘low likelihood’ (LL). Test-retest reliability was tested in 73 of these patients.
Results:
Subject characteristics – 79% smoked >10 pack-years; M:F = 56:44; 57% were aged >60; previous diagnoses were asthma (64%), COPD (44%) or both (13%). Utility of DDQ — HL Cutpoint: Sensitivity = 63%, Specificity = 76%, Positive Predictive Value = 67%. LL Cutpoint: Sensitivity =82%, Specificity = 44%, Positive Predictive Value= 77%. Area under the Receiver Operating Curve=0.72 (moderate diagnostic agreement between DDQ and spirometry). Reliability was good (kappa=0.78). These characteristics are similar to those previously obtained from UK/US, though some symptoms in Australia appear less helpful in contributing to the differential diagnosis model.
Conclusions:
The DDQ is a valid and reliable tool for helping GPs in Australia differentiate patients with a high likelihood of COPD from those unlikely to have COPD. Further work may help to develop greater discriminative value for the DDQ in Australia, enabling the GP to prioritise patients more effectively for spirometry confirmation.
Conflict of interest and funding
Covance was supported by Boehringer Ingelheim Pty Ltd and Pfizer Australia Pty Ltd.
Article PDF
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Frith, P., Attewell, R., Crockett, A. et al. ABS49: Splitting COPD and asthma: Validation of the differential diagnosis questionnaire (DDQ) in Australian primary care. Prim Care Respir J 15, 198 (2006). https://doi.org/10.1016/j.pcrj.2006.04.144
Issue Date:
DOI: https://doi.org/10.1016/j.pcrj.2006.04.144