Quality control of cancer screening examination procedures in the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial

Investigators for the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial describe quality control procedures for the digital rectal examination, ovarian palpation examination, transvaginal ultrasound, chest X-ray, and flexible sigmoidoscopy. These cancer screening tests are subject ive and difficult to standardize. PLCO quality control procedures aim to me asure and, where possible, reduce variation, across examiner and screening center, with respect to cancer screening test performance. Initial protocol s stressed examiner qualifications, experience, and training; equipment spe cifications; examination procedures; and definitions for positive tests. Th e PLCO quality assurance subcommittee developed a final quality assurance p lan, which included central approval and registration of PLCO examiners, di rect observation of screening test performance during periodic site visits by the National Cancer Institute and coordinating center auditors, periodic analysis of screening test data, and procedures for independently duplicat ing or reviewing selected examinations. For each modality, the periodic dat a analyses examine the test-positive and the test-inadequate proportions an d aim to identify divergent centers or examiners. Procedures for duplicatin g examinations specify feasible sample sizes for precise estimates of agree ment between examiners, at each center, for each screening test modality, a nd over a 1-year period. These quality control procedures will help charact erize the consistency and reliability of the PLCO cancer screening tests. C ontrol Clin Trials 2000;21:390S-399S (C) Elsevier Science Inc. 2000.