Analytic inaccuracy and imprecision in reticulocyte counting: a preliminary report from the College of American Pathologists Reticulocyte Project.

Precision and accuracy of reticulocyte counting appears to require significant improvement. Several poorly controlled analytic variables affect reticulocyte count performance including sample size, use of an ocular insert, interobserver variation in reticulocyte definition, and possibly the type of blood smear evaluated. These sources of imprecision and inaccuracy are discussed, and new data from the initial phases of the College of American Pathologists assessment of reticulocyte counting are presented. Recommendations for analytic goals for both manual and automated reticulocyte counting are provided.