Misinterpretation of the chest x ray as a factor in the delayed diagnosis of lung cancer.

All patients in 1997 with a histologically proved diagnosis of lung cancer in Castle Hill Hospital in whom a full set of case notes and x rays could be retrieved were studied. All previous chest x rays were reviewed by a consultant chest physician and a radiologist, who were blinded to the eventual site of the lesion and the point at which a suspicious abnormality first appeared. Case notes were inspected to clarify the cause of any error. Fifty eight patients were eligible, 28 of whom had previous chest x rays. Of these 14 were found to be abnormal. A significant difference (p=0.007) in time from diagnosis to death was found between those with a missed abnormality, median (interquartile range, IQR) 105 (55-219) days and those with no previous abnormality, median (IQR) 260 (137-512) days. In the 14 in whom the diagnosis was missed the median (IQR) delay from first abnormal chest x ray to the eventual diagnostic x ray was 101 (48-339) days. A significant difference (p=0.001) was also found between the median (IQR) time from first abnormal chest x ray to start of treatment between those with missed abnormalities, 155 (115-376) days, and those with no previous abnormality on chest x ray, 51 (44-77) days. The most common reason (47%) for the diagnosis to be missed was failure of the radiologist reporting the x ray to recognise the abnormality. It is not unusual to find previous significant radiological abnormalities in patients in whom a diagnosis of lung cancer is later made. This leads to a diagnostic delay which has a significant effect on time to initiation of treatment and palliation of symptoms, although not necessarily to eventual outcome.