Data were collected on procedures that were part of a diagnostic work-up for lung cancer and for staging procedures following a diagnosis. Two different types of events triggered the collection of diagnostic procedure information among LSS and ACRIN participants:

1. Screens suspicious for lung cancer: Among approximately 27,000 participants in each arm screened once a year for up to 3 years, there were about 18,000 screening CT exams and 5,000 screening x-ray exams suspicious for lung cancer (positive screens). Participants with positive screens were advised to receive further follow-up from a doctor outside the trial. Follow-up procedures were systematically captured, in most cases for up to one year following the screen (two years following a positive T2 screen, if a conclusive result was not reached after one year of follow-up). Any participant receiving a positive screen was recommended for further follow-up. This information was captured regardless of the eventual diagnosis.
2. Confirmed diagnoses of lung cancer: When a participant was diagnosed with lung cancer within the trial period, diagnostic procedures that occurred in the year leading up to that diagnosis were captured in the data. This is the only source of diagnostic procedure information in the years after the conclusion of screening.

If a participant had a diagnostic procedure during the trial such that it was neither one year following a positive screen (up to two years for T2) nor one year prior to a lung cancer diagnosis, that information was not systematically captured by NLST and is not available in the datasets.

For many purposes, diagnostic procedure data can be obtained within the Participant dataset. Additional details are contained within the Diagnostic Procedures dataset (one record per procedure per person) and the Medical Complications dataset (one record per complication per person).

Summary	Available Data
~61,000 procedures among ~13,000 participants Collected for the year following a positive screen (up to two years for positive T2 screens) Collected for the year preceding a lung cancer diagnosis Collected on the following forms: LSS DE (PDF - 183 KB) ACRIN ZX (ACRIN NLST CRF Set)	Whether screens prompted diagnostic procedure(s) Whether screens triggered biopsies Available in diagnostic procedures dataset Types of procedures Days from randomization to procedure Whether procedure was linked to a positive screen and/or a cancer diagnosis Medical complications dataset