RBC indices are calculated mean values that reflect the size, weight, and Hgb content of individual erythrocytes. They consist of the mean corpuscular volume (MCV), the mean corpuscular hemoglobin (MCH), and the mean corpuscular hemoglobin concentration (MCHC). MCV indicates the volume of the Hgb in each RBC, MCH is the weight of the Hgb in each RBC, and MCHC is the proportion of Hgb contained in each RBC. MCHC is a valuable indicator of Hgb deficiency and of the oxygen-carrying capacity of the individual erythrocyte. A cell of abnormal size, abnormal shape, or both may contain an inadequate proportion of Hgb.
RBC indices are used mainly in identifying and classifying types of anemias. Anemias are generally classified according to RBC size and Hgb content. Cell size is indicated by the terms normocytic, microcytic, and macrocytic. Hemoglobin content is indicated by the terms normochromic, hypochromic, and hyperchromic. Table 1-6 shows anemias classified according to these terms and in relation to the results of RBC indices.
To calculate the RBC indices, the results of an RBC count, Hct, and Hgb are necessary. Thus, factors that influence these three determinations (e.g., abnormalities of RBC size or extremely elevated WBC counts) may result in misleading RBC indices. For this reason, a stained blood smear may be used to compare appearance with calculated values and to determine the etiology of identified abnormalities.
| Men | Women | Newborns | SI Units | |
|---|---|---|---|---|
| MCV | 80-94 µm3 | 81-99 µm3 | 96-108 µm3 | 81-99 fL (women) 96-108 fL (newborns) |
| MCH | 27-31 pg | 27-31 pg | 32-34 pg | 32-34 pg (women) 32-34 pg (newborns) |
| MCHC | 32-36% | 32-36% | 32-33% | 320-360 g/L (women) 320-330 g/L (newborns) |
Normal values for RBC indices are shown in Table 1-4 in relation to the CBC and also are repeated above for adults. Values in newborn infants are slightly different, but adult levels are achieved within approximately 1 month of age.
Because RBC indices are calculated from the results of the RBC count, Hgb, and Hct, factors that influence the latter three tests (e.g., abnormalities of RBC size, extremely elevated WBC counts) also influence RBC indices.
Nursing Care Before the Procedure
Client preparation is the same as that for any study involving the collection of a peripheral blood sample (see Appendix I).
A venipuncture is performed and the sample collected in a lavender-topped tube. A capillary sample may be obtained in infants and children as well as in adults for whom venipuncture may not be feasible.
Nursing Care After the Procedure
Care and assessment after the procedure are the same as for any study involving the collection of a peripheral blood sample (see Appendix I).