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Introduction ⬇

Individual cell size is the best index for classifying anemias. This index expresses the volume occupied by a single erythrocyte and is a measure in cubic micrometers (femtoliters [fL]) of the mean volume. The MCV indicates whether the RBC size appears normal (normocytic), smaller than normal (less than 82 μm3, microcytic), or larger than normal (more than 100 μm3, macrocytic).

Normal Findings ⬆ ⬇

82–98 mm3 or 82–98 fL (higher values in infants and newborns and for older patients)

Procedure ⬆ ⬇

  1. Calculate the MCV from the RBC count (the number of cells per cubic millimeter of blood) and the Hct (the proportion of the blood occupied by the RBCs).

  2. Use the following formula:

Clinical Implications ⬆ ⬇

The MCV results are the basis of the classification system used to evaluate an anemia. The categorizations shown in Chart 2.1 aid in orderly investigation.

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain test purposes and procedures.

  2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Review test results; report and record findings. Modify the nursing care plan as needed. Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment.

  2. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆

  1. Mixed (bimorphic) population of macrocytes and microcytes can result in a normal MCV. Examination of the blood film confirms this.

  2. Increased reticulocytes can increase the MCV.

  3. Marked leukocytosis increases the MCV.

  4. Marked hyperglycemia increases the MCV.

  5. Cold agglutinins increase the MCV.