Hospital‐activity data inaccurate for determining spread‐of‐disease at diagnosis for non‐small cell lung cancer

Objective:Accurate information on spread‐of‐disease at diagnosis would increase the usefulness of hospital‐activity data for cancer research. This study evaluates the accuracy of codes recorded in hospital‐activity data to assign spread‐of‐disease at diagnosis for non‐small cell lung cancer (NSCLC).Methods:The reference (gold) standard was TNM stage as assigned at a multi‐disciplinary meeting. To allow comparison with hospital‐activity data, TNM stage was mapped to spread‐of‐disease (local, regional, distant). Sensitivity, specificity and positive‐predictive values were stratified by whether the patient had surgery.Results:Data from the reference standard and hospital‐activity database were available for 2,184 patients. According to the reference standard, local disease was present for 57.0% of surgical patients and 12.6% of non‐surgical patients at diagnosis. Hospital‐activity data over‐estimated patients with local disease (surgical: 71.9%, non‐surgical: 48.5%). There was a corresponding underestimation of distant spread‐of‐disease: surgical (reference standard: 4.0%, hospital‐activity data: 2.7%); non‐surgical (reference standard: 45.9%, hospital‐activity data: 36.8%). This meant that hospital‐activity data had good sensitivity but poor specificity for local disease; and poor sensitivity, but good specificity for metastatic disease.Conclusion:Secondary diagnosis codes in hospital activity data do not accurately capture spread‐of‐disease at diagnosis for patients with non‐small cell lung cancer; even when the clinical notes contain TNM clinical stage as documented at a multidisciplinary meeting.Implications:Changes are needed to coding rules, and the ICD codes themselves, to allow for coding of regional and distant spread without specification of the precise site.