Laboratory Diagnostic Tests

RETICULOCYTES COUNTS

Reticulocytes in the peripheral blood are young erythrocytes, observed as polychromatophilic cells because they contain residual RNA.
Reticulocytes require supravital stains brilliant cresyl blue or methylene blue for an accurate identification and enumeration. Smears are prepared, and the cells containing stained precipitates (reticulum) are counted manually under the microscope. The areas of the smear where cells do not overlap are examined under an oil immersion lens, and the number of cells containing any blue granules or reticulum occurring among 1,000 erythrocytes are counted. The counts can be expressed as percentage (number of reticulocytes per 100 erythrocytes), or in absolute numbers per liter.
Automated methods are based on flow cytometry of erythrocytes stained with fluorescent dyes (Technicon H3, Sysmex, and Abbot).

Reference values