Children's blood routine test: correct interpretation of red blood cells and reticulocytes!

Author: Song Wenqi, National Children's Medical Center (Beijing), Chief Technician, Beijing Children's Hospital, Capital Medical University

Reviewer: He Yanling, Chief Physician, Beijing Chaoyang Hospital, Capital Medical University

In pediatric outpatient clinics, routine blood tests are a very common examination item. Many parents always have various questions when they receive their children's routine blood test reports. Today, let's talk about the clinical significance of these two common indicators, red blood cells and reticulocytes!

1. What disease may be caused by increased or decreased red blood cells in children’s blood routine?

The reference range (normal value range) of red blood cells varies for children of different ages. The reference range of red blood cell count on the first day after birth is (5.7-6.4)×1012/L; the reference range in the first week is (5.2-5.7)×1012/L; the reference range in the second week is (4.2-5.2)×1012/L; the reference range from 28 days to less than 6 months is (3.3-5.2)×1012/L; the reference range from 6 months to less than 6 years is (4.0-5.5)×1012/L; the reference range from 6 years to less than 13 years is (4.2-5.7)×1012/L; the reference range from 13 to 18 years is (4.5-5.9 for boys and 4.1-5.3 for girls)×1012/L. The reference range for healthy adult males is (4.3-5.8)×1012/L; the reference range for healthy adult females is (3.8-5.1)×1012/L.

Red blood cells are produced by the bone marrow and released into the blood. They are the most numerous cells in the blood. The main functional molecule in red blood cells is hemoglobin, which accounts for 90% of the red blood cell components.

The main function of red blood cells is to transport oxygen from the lungs to various tissues of the body through the blood, helping the tissues to metabolize. Therefore, a large number of red blood cells age and die every day, and new red blood cells are replenished at the same time, and the two are in a dynamic balance.

Under pathological conditions, the number of red blood cells can increase or decrease. The pathological conditions of erythrocytosis include relative increase and absolute increase.

Relative increase is mainly seen in dehydration caused by various reasons. Because the blood volume decreases, the red blood cells will increase relatively. Severe vomiting, very severe diarrhea, large-area burns, heavy sweating, polyuria and oliguria can all cause a relative increase in red blood cells.

The absolute increase is mainly due to secondary erythrocytosis caused by tissue hypoxia. For example, chronic cor pulmonale and cyanotic congenital heart disease are caused by an increase in the number of red blood cells due to hypoxia, which helps the body carry enough oxygen to maintain physiological needs. In some diseases, such as polycythemia vera, the patient's red blood cell count can be as high as (7.0-10.0)×1012/L.

Figure 1 Original copyright image, no permission to reprint

Erythropenia is mainly seen in various anemias. The cause may be bone marrow hematopoietic dysfunction, which causes erythropenia. It is common in aplastic anemia, acute leukemia, chronic leukemia and myelodysplastic syndrome.

Lack of hematopoietic raw materials or impaired utilization can also cause anemia, such as iron deficiency anemia caused by iron deficiency, and megaloblastic anemia caused by vitamin B12 and folic acid deficiency.

Massive consumption of red blood cells can cause hemolytic anemia; acute and chronic blood loss due to gastrointestinal bleeding, tumors, hookworm disease, etc. can cause hemorrhagic anemia.

2. What disease may be caused by increased or decreased reticulocyte count in children’s blood routine test?

The reticulocyte percentage varies with age. The normal range for newborns is 2%-6%, and the normal range for children and adults is 0.5%-1.5%; the normal range for the absolute value of reticulocytes is (22-139)×109/L.

Reticulocytes are precursor cells in the maturation of red blood cells. Cell morphology under a microscope shows that mature red blood cells do not have a nucleus, while immature red blood cells have a nucleus. In the process of immature red blood cells shedding their nuclei and developing into mature red blood cells, there are remnants of basophilic RNA in their cytoplasm. After the remnants aggregate, they form a network in the cytoplasm, so this precursor cell is called a reticulocyte.

Reticulocytes are red blood cells that are about to mature and account for 1% of the red blood cells in the blood. If the reticulocytes continue to mature, they will form mature red blood cells after 24-48 hours.

The reticulocyte count is of great clinical significance. On the one hand, it can help us judge the proliferation of the bone marrow erythrocyte system. For example, when the reticulocyte count increases, it generally indicates that the erythroid proliferation in the bone marrow is vigorous, which can be seen in various anemias, such as hemolytic anemia, iron deficiency anemia, megaloblastic anemia, sideroblastic anemia, etc.

When the reticulocyte count decreases, it often indicates a decrease in bone marrow hematopoietic function, which can be seen in aplastic anemia.

The biggest advantage of reticulocyte testing is that it helps us determine the effectiveness of anti-anemia treatment.

Figure 2 Original copyright image, no permission to reprint

When a patient is anemic, anti-anemia drugs such as iron supplements are given to him. If the patient's bone marrow hematopoiesis is relatively active, the reticulocyte count will increase, indicating that this treatment method is effective. On the contrary, if the patient's bone marrow hematopoiesis is inactive, the reticulocyte count will not change, indicating that the treatment method is ineffective.

Therefore, observing the reticulocyte count is of great significance when evaluating the effect of anemia treatment.