Introduction
Anemia is a complication caused by several chronic diseases, chronic kidney disease (CKD) in particular. Anemia can be defined as reducing the total number of circulating red blood cells (RBCs). Anemia is considered when there is a decrease of the following, RBC count, the concentration of hemoglobin, and hematocrit. When laboratory tests show this condition’s existence, it is a signal that a disease can be present. Therefore anemia should be diagnosed. There are several etiologic categories of anemia. The paper will, in detail, discuss the background of anemia, such as epidemiology, physiology, and etiology. Diagnosis of anemia will also be including assay choice, testing frequency, and laboratory analysis of current markers. The essay will focus mainly on the biochemistry laboratory’s role in assessing anemia’s clinical management as a CKD-related complication.
Background
Anemia was linked to CKD for the first time over 170 years ago. According to New, Et, Al, (2015) , the progress of kidney disease increases the prevalence of anemia increase. This affects almost every patient with CKD stage 5. CDK’s related anemia reduces life quality, increases cardiovascular disease, mortality, and cognitive impairment. CKD anemia is typically normochromic, hyperproliferative, and normochromic. A hypothesis in the 1950s engendered that erythropoietin (EPO) deficiency was the main cause of CKD anemia. Cloning and purification of EPO in the early 1980s helped develop immunologic assays that quantified circulating EPO levels. Levels of EPO are inappropriately considered relatively low to the degree of anemia….. The main limitation of these assays is that all immunogenic EPO fragments are measured, and all of them do not correlate to biological activity.
In the 1980s, the management of anemia was revolutionized by the introduction of recombinant human EPO. The major benefit of this revolution was that patients debilitating symptoms were improved, which freed them from depending on blood transfusion. Iseki, & Kohagura, (2017). However, there was a negative effect on patients who were receiving erythropoiesis-stimulating agents (ESAs). It led to a worsening of the patient’s hypertension and clotting of dialysis access. Additionally, negative results that are associated with anemia were not reduced by ESAs. Apart from the deficiency of EPO, there are other causes of CKD anemia.
Etiologically, anemia can be categorized into three categories. They include increased RBC destruction, decreased production of RBC and loss of blood. Both anemias of CKD and anemia of chronic illness are in the category of decreased production of RBCs. However, CKD anemia can be classified as normochromic and normocytic anemia.
Kidney and Their Functions
Kidneys are two almost equal bean-shaped organs. Kidneys are located below the rib cage. Their function is to filter blood to produce urine. Healthy kidneys produce erythropoietin (EPO) hormone. The role of hormones is to trigger or help in regulating specific body functions. EPO’s role is prompting bone marrow to produce red blood cells, which carry oxygen in the body.
Causes of CKD Anaemia
In a damaged or diseased kidney, the production of EPO is low and not enough. As a result, fewer red blood cells are made by the bone marrow; this causes anemia. When red blood cells are few in the blood, the body has deprived of the oxygen that it needs.
Another anemia cause in diseased kidney patients is the loss of blood in hemodialysis. According to Singh Et.Al, (2016) low levels of iron, folic acid, and vitamin B12 are another cause of CKD anemia. The blood requires such nutrients in making hemoglobin, which is the main carrier of oxygen in red blood cells.
Other causes of anemia include bone marrow problem, inflammatory problems such as lupus and arthritis, malnutrition and chronic infections like diabetic ulcers. However, these causes are checked by health care providers when treatment of kidney-related anemia fails to work.
Laboratory Evaluation
Even if physical examination and patient history may indicate anemia’s presence and cause, comprehensive evaluation from the laboratory is necessary for definitive diagnosis and treatment of CKD-related anemia. O’Mara, (2017). Thus, there are several tests to diagnose anemia with hematological routine tests like reticulocyte counts and CBC as well as iron status study, which help as a point of leaping anemia diagnosis. Several specific tests are done to diagnose the specific condition of anemia. Most laboratory tests use quantitative and semiquantitative red blood cells and supplementary testing of body fluids and blood. Laboratory outcomes from such parameters are crucial arguments in treatment, diagnosis and anemia monitoring.
The first step in diagnosing anemia, which is related to CKD, is detection with accurate predictive tests from laboratories to get clues of underlying health conditions and diseases. This process helps to prevent subjecting patients to tests and treatments of anemia that do not exist.
In the past decade, there has been remarkable progress in algorithms, tests, and CKD anemia diagnosis. The main procedure for investigating anemia is CBC. In the first step, microcytic RBCs are considered. MCV, RBC, and RDW are considered in the second step, and they are examined. Innovative algorithms and parameters are advocated in reflecting RBC hemoglobinization and reticulocytes. This helps in differentiation between types of anemias, their cause and treatment. Currently, automated counts of reticulocytes help in providing new parameters to evaluate marrow activity. As a result, establishing reliable and accurate criteria for the specific cause of anemia identification and evaluation of impact intervention strategies is important. After all these, mandatory and simple laboratory tests should follow.
The table below summarizes laboratory tests used to diagnose anemia.
Complete Blood Count
Before developing the current blood analyzers of hematology, blood counts included white blood cell count, manual platelet and hemoglobin concentration. Parameters like hematocrit (Hct), RBC count and hemoglobin concentration (Hb) had to be calculated mathematically. Modern analyzers use chemical and physical methods like electronic impedance. Light absorption, staining properties, and scattering of laser light to provide CBC.
CBC identifies different parameters, which provides important information in the testing of CKD anemia. Biochemical and hematologic variations of red blood cells help to know the anemic status of a patient. When the patient is anemic, MCV helps in providing probable causes of anemia. Abnormal number or size of platelets might be caused by either effect of existing disease of blood or by reflecting the existence of other underlying pathologies. Walters, & Abelson, (2014). Due to this, a curious and careful reassessment of clinical evaluation is important. Fundamental parameters are discussed below:
- Hemoglobin (Hb) concentration
The intense color of hemoglobin is used in determining the concentration of blood. A mixture of oxyhemoglobin, hemoglobin, methemoglobin and carboxyhemoglobin is contained in erythrocytes. Hb is usually used in laboratories to screen and determine how severe anemia is. A systematic clinical approach is required when there is an increase in Hb concentration. Buttarello, (2016). This leads to further investigation and diagnosis. According to Otto, Et.Al, (2017), levels of Hb can rise due to congestive heart failure and chronic pulmonary diseases, among others.
- Count of red blood cell
RBC count is one of the most efficient and most recognized measurements in laboratories for diagnosing anemia. An increase in RBC count can be a result of a chronic increase in erythropoiesis. As a result, MCH and MCV are low in beta-thalassemia compared to deficiency of iron in anemia.
- Hematocrit
This is where plasma and blood cells are separated in the laboratory by centrifugation to enable test mechanisms. Low values of Hct indicate the presence of anemia. If Hct is less or equal to thirty percent, then the patient has severe anemia.
Red Blood Cells Indices
Red blood cell indices are hemoglobin content and size. In modern laboratories, these indices are obtained using automated instruments. In the laboratory, different instruments vary depending on the technologies used. A combination of the electric field, radiofrequency and light, which is highly focused, is used to separate the cells. Apart from being fast, automated instruments are also very accurate, with an error variation of two percent.
Mean Corpuscular volume (MCV)
MCV is normally used to test and diagnose CKD-related anemia. Despite MCV being highly reproducible and accurate, the introduction of errors by agglutination of RBC and distortion of the cell’s shape might happen. Results of MCV form the basis of the classification system used to evaluate anemia. Thomas, Et.AL, (2018).
| • |
| Microcytic anemias (MCV 50–79 fL) | |
| Disorders of iron metabolism | Iron deficiency anemia, anemia of chronic disease, congenital hypochromic-microcytic anemia with iron overload |
| Disorders of porphyrin and heme synthesis | Acquired sideroblastic anemias, idiopathic refractory sideroblastic anemia |
| Disorders of globin synthesis | Thalassemias, hemoglobinopathies, characterized by unstable hemoglobins |
| Normocytic normochromic anemia (MCV 80–98 fL) | |
| Anemia with appropriate bone marrow response | acute posthemorrhagic anemia, hemolytic anemia |
| Anemia with impaired marrow response | Aplastic anemia, pure red blood cell aplasia, myelofibrosis |
| Macrocytic anemias (MCV 99–150 fL) | |
| Cobalamin (B12) deficiency | Lack of animal products, intrinsic factor deficiency, pernicious anemia, hyperthyroidism, pregnancy, enzyme deficiencies. |
| Folate deficiency | Lack of vegetables, celiac disease, hypothyroidism, folic acid antagonists, hemodialysis |
| Unresponsive to cobalamin or folate | Metabolic inhibitors (i.e., 6-mercaptopurine), inborn errors (Lesch-Nyhan Syndrome) |
The flowchart below is followed to show anemia diagnosis, according to MCV.
Red Blood Cell Distribution Width (RDW)
This is an estimate of volume variance within the red blood cell population. Automated counters are used in providing RDW. RDW can be expressed as a variation coefficient (%) or as SD (fL) of red cell volume. Pulse height analysis is used to derive RDW. Two methods are used by automated counters to calculate RDW. The first method is known as RDW-CV. This is the ratio of red blood cell width at SD, divided by MCV. Any changes in MCV or width of the curve influences the result. The second method of measuring RDW is known as RDW-SD. This method is independent of MCV. The two RDW measurements are mathematical statements of anisocytosis.
Stained Peripheral Blood Smear
This a method used in laboratories to obtain additional information about CKD-related anemia. It is a manual investigation that is prepared using glass slides. This method is used in the laboratory only when the patient’s indices are not normal, i.e., there is a major change from previous CBCs. A film is requested when any disorder of blood is suspected. At this stage, automated laboratory instruments are used to determine RBC indices and counts accurately. This method is a complement automated counter measurement of MCH and MCV.
| abnormal RBCs | Comment |
| Macrocyte | Larger than normal (>8.5 μm diameter) |
| Microcyte | Smaller than normal (<7 μm diameter) |
| Hypochromic | Less hemoglobin in the cell. The enlarged area of central pallor
Loss of central pallor, stains more densely, often microcytic. |
| Spherocyte | Hereditary spherocytosis and certain acquired hemolytic anemias |
| Target cell | Hypochromic with central “target” of hemoglobin. Liver disease, thalassemia, Hb D, and post-splenectomy |
| Leptocyte | Hypochromic cell with a normal diameter and decreased MCV. Thalassemia |
| Elliptocyte | Oval to cigar-shaped. Hereditary elliptocytosis, certain anemias (particularly vitamin B12 and folate deficiency) |
| Stomatocyte | Slit-like area of central pallor in the erythrocyte. Liver disease, acute alcoholism, malignancies, hereditary stomatocytosis, and artifact |
| Acanthocyte | Five to ten spicules of various lengths and at irregular intervals on the surface of RBCs |
| Echinocyte | Evenly distributed spicules on the surface of RBCs, usually 10–30. Uremia, peptic ulcer, gastric carcinoma, pyruvate kinase deficiency, and preparative artifact |
| Sickle cell | Elongated cell with pointed ends. Hb S and certain types of Hb C |
Variations in color, shape, and inclusion of bodies and staining in blood smear indicate RBC abnormalities and a diagnosis of diseases.
Conclusion
There is no specific marker or combination of tests for diagnosing CKD-related anemia. Physicians’ experience and knowledge who demand biochemical tests related to preliminary diagnosis play an important role in anemia diagnosis. Although in the underlying condition of CKD, there is a high probability of anemia complications arising, it is always recommended that algorithms be used to determine anemia tools so that laboratory tests can be reduced while accurately diagnosing the underlying cause in patients.
References
New, J. P., Aung, T., Baker, P. G., Yongsheng, G., Pylypczuk, R., Houghton, J., … & O’Donoghue, D. J. (2015). The high pr; evidence of unrecognized anemia in patients with diabetes and chronic kidney disease: a population‐based study. Diabetic Medicine, 25(5), 564-569.
O’Mara, N. B. (2017). Anemia in patients with chronic kidney disease. Diabetes Spectrum, 21(1), 12-19.
Otto, J. M., Plumb, J. O., Clissold, E., Kumar, S. B., Wakeham, D. J., Schmidt, W., … & Montgomery, H. E. (2017). Hemoglobin concentration, total hemoglobin mass and plasma volume in patients: implications for anemia. Haematologica, 102(9), 1477-1485.
Iseki, K., & Kohagura, K. (2017). Anemia as a risk factor for chronic kidney disease. Kidney International, 72, S4-S9.
