Retraction of: External Quality Assessment Programs in the US with an emphasis on urinary sediment testing: the College of American Pathologists experience.

The College of American Pathologists (CAP) has maintained the highest standards for laboratory medicine through education, evaluation, and certification. One form of External Quality Assurance - proficiency testing (PT) - is the centerpiece of that mission. Over 500 medical and scientific experts oversee CAP PT programs which include more than 600 tests performed by 22,000 laboratories in over 100 countries. It is the most comprehensive laboratory peer-review comparison program in the world. The CAP offers four urine sediment PT products tailored to the needs of different laboratories. Each includes three or four digital images, shipped twice a year. The program is overseen by the Hematology and Clinical Microscopy Resource Committee. Images are graded if there is 80% or greater consensus of either referee or participant laboratories. Failing laboratories must analyze the reasons for the failure, report the results, and initiate corrective action. Over the years, there has been a progressive decline in the number of errors, demonstrating that education and regulatory oversight are major contributors to improved PT performance and, by extension, patient care. The PT urine sediment image databank is a unique resource, representing the consensus of many laboratories. Participant and referee responses identify which morphologic variants are unambiguous and which are more difficult to classify. The PT challenges include discussions of disease pathophysiology and key morphologic features. This teaching component is what helps to set the CAP's program apart. The discussions formed the basis for the Color Atlas of Urinary Sediment published by the CAP in 2010.