After an automated complete blood count (CBC) analysis has determined that abnormal RBC morphology may be present, a well-made and well-stained peripheral blood smear should be reviewed. When a peripheral blood smear is made for the purpose of evaluating RBC morphology, accurate recognition and identification of RBC morphologic abnormalities can be an invaluable aid in the diagnosis of a variety of disorders.
RBC morphology reporting formats can vary among laboratories. Despite the standardization of many laboratory technologies and test result formats, there are still various protocols in use in the area of red cell morphology reporting. Current methods of reporting and quantifying red cell morphology include descriptive terms such as 'rare,' 'occasional,' 'many,' 'slight,' or 'moderate,' as well as numerical gradings of 1+, 2+, 3+, etc.
Regardless of the terminology used, consistency is of greater importance. There must be a defined, semi-quantitative scheme that dictates how many cells with a specific morphologic abnormality qualify as "rare" or "many," and so on. The report format must be clear and useful to the physician. Some morphologic abnormalities are quite specific and diagnostic, but others are ambiguous and of little diagnostic significance.
A well-defined, semi-quantitative report format for RBC morphology should be based on clinical significance. Some morphologic abnormalities are significant, even when they occur in very low numbers. These include:
- Fragmented red cells (eg, schistocytes, helmet cells, keratocytes/horn cells)
- Sickle cells
- Teardrop cells
- Polychromatophilic cells
Other morphologic abnormalities are significant only when seen in considerable numbers. These include:
- Burr cells (echinocytes)
- Target cells
- Hypochromic cells
A final category includes morphologic abnormalities that are significant but do not need to be quantified as it serves no purpose; these findings can be noted as "present." These include
- RBC agglutination
- Dimorphic or double red cell population
An example of a standardized reporting format is given on the following page.