Registration of lung cancer in Scotland: an assessment of data accuracy based on review of medical records

Lung cancer represents a major public health problem in Scotland. Cancer registration data permit the approximate incidence of this disease to be measured directly and the projected incidence to be modelled. Thus, in addition to epidemiologic studies and survival analyses, cancer registration data may be used for planning and monitoring relevant health services. Since the value of the data depends on their quality, we undertook a largescale study of the accuracy of cancer registration data in Scotland. The medical records of a random sample of cancer registrations attributed to the year 1990 were sought. The sample contained 340 registrations of lung cancer, 309 (91 percent) of which had relevant medical records available for scrutiny. Registration details were reabstracted from available records and compared with data in the registry. Results revealed 19 discrepancies in identifying items of data (surname, forename, gender, and date of birth) involving 16 (5.2 percent) patients. Most were trivial and would not disturb record linkage. Discrepancy rates were found to be: 7.8 percent in postcode of residence at the time of diagnosis, 10 percent in ‘anniversary date’ (excluding differences of six weeks or less), 12.5 percent in histologic verification status; 4.2 percent in ICD-9 site code (the first three digits), and 15.5 percent in four digit ICD-O morphology code (excluding ‘inferred’ morphology codes). This relatively high level of accuracy gives weight to routinely published incidence figures and supports the use of these data for exploratory epidemiologic studies, assessment of health care needs, and calculation of survival.