Background
Lung cancer is the leading cause of cancer death worldwide. The UK relies more heavily upon chest x-ray than many other high income countries. Little is known about the performance of the test, the risk of cancer following negative test, consequences of ‘false negative’ results and the factors that affect how frequently chest x-ray is used.
Aims
1. Determine sensitivity and specificity of chest x-ray.
2. Determine if there are differences in outcomes between patients with ‘true positive’ versus ‘false negative’ chest x-rays.
3. Determine the risk of lung cancer following a negative chest x-ray with respect to symptoms.
4. Quantify the volume of chest x-rays undertaken by English general practices and understand the extent to which variations in chest x-ray frequency are due to differences in patient populations and the practices themselves.
Methods
1. Systematic review on sensitivity of chest x-ray
2. Observational study to determine sensitivity and compare stage and survival between those with ‘true positive’ versus ‘false negative’ results.
3. Cohort study to determine chest x-ray specificity and lung cancer risk following negative chest x-ray.
4. Retrospective study to quantify general practices’ chest x-rays with respect to characteristics of their patient populations and the practices.
Results
1. Sensitivity was 77-80% (systematic review) and 82% (observational study). Specificity was 90%.
2. ‘False negative’ chest x-rays were not associated with adverse outcomes, although given the retrospective methodology this cannot be excluded.
3. Lung cancer risk following negative chest x-ray was <1% for all symptoms except haemoptysis (3%).
4. There was substantial variation in chest x-ray utilisation (median 34/1000 patients, IQR 26-43), with 18% of variance accounted for by recorded characteristics.
Conclusions
Chest x-ray does not identify ~20% of lung cancers but it continues to have a useful role. The substantial variation in rates of investigation suggest that it may be underutilised in many practices.
