H
Haptoglobin
Purpose of the test
Haptoglobin measurement is useful in the workup for hemolytic conditions. It also is used for monitoring of acute reactions that involve hemolysis of erythrocytes.
Basics the nurse needs to know
When erythrocytes undergo hemolysis by normal or abnormal processes, circulating haptoglobin binds to the free hemoglobin. These newly formed complexes cannot be filtered through the renal glomeruli so hemoglobin cannot be excreted in the urine. As the complexes are broken down, iron is conserved and stored for use in the manufacture of new erythrocytes.
Decreased values
A decreased value is more useful as a laboratory test. Decreased values occur with conditions of abnormal hemolysis of red blood cells. The decrease may be gradual, chronic, or sudden and severe in occurrence. In acute hemolysis, a severe decline in haptoglobin will occur. As the red blood cells are destroyed, available haptoglobin is rapidly consumed by the reticuloendothelial system.
Interfering factors
NURSING CARE
Nursing actions are similar to those used in other venipuncture procedures (see Chapter 2), with the following additional measures.
Posttest
Helicobacter pylori tests
Purpose of the test
This test establishes the presence of Helicobacter pylori infection that can cause chronic, active gastritis and peptic ulcers.
Basics the nurse needs to know
H. pylori is a gram-negative bacillus that resides under the mucosal layer, attached to the gastric epithelial tissue. It causes gastritis, is the main cause of ulcers in the stomach, and may be one cause of gastric cancer. The infection is usually acquired in childhood, particularly in people who are poor or who reside in developing countries where poor sanitary conditions and a lack of running water prevail. If the infection has not been eradicated in childhood, it remains as a lifelong infection, with or without symptoms. There are several different tests to confirm the H. pylori infection and to document its eradication. The tests are classified as noninvasive and invasive.
Noninvasive testing
Serology antibody test
This frequently used blood test identifies the elevated level of immunoglobulin G (IgG) antibody to the H. pylori antigen in the symptomatic patient. The positive test result indicates current or past infection. After treatment, it cannot document that infection has been eliminated.
Urea breath test
If H. pylori is present, the organism produces a unique enzyme, urease. Radiolabeled carbon urea is administered to the patient orally. The urease converts the carbon urea to ammonia and radiolabeled carbon dioxide (CO2) gas. The radiolabeled CO2 enters the blood and is then exhaled by the lungs. The test measures the radiolabeled CO2 in the exhaled air, demonstrating that the patient has an infection with H. pylori. When the urea breath test is conducted 7 days or more after completing the prescribed course of antibiotics, a negative result is proof that the infection has been eradicated. The test is highly accurate and widely used.
Invasive testing
Esophagogastroduodenoscopy with tissue biopsy
During the endoscopy procedure, the gastric and duodenal mucosa are examined, and a biopsy is taken of suspicious lesions and areas of inflammation or ulceration. In the laboratory, biopsy tissue slides are prepared and stained for microscopic examination. When present, the characteristic H. pylori bacteria are seen and identified. Additional laboratory tests on the biopsy samples are done, including those identified below. This testing approach is very accurate.
H. pylori produces a unique enzyme called urease. The urease can be detected by chemical analysis of the tissue sample. The presence of urease presumes the presence of H. pylori.
From the tissue specimen, polymerase chain reaction (PCR) technique amplifies the DNA sequence of H. pylori bacillus. The microbe is identified by its DNA blueprint.
How the test is done
Interfering factors
NURSING CARE
Pretest
Instruct the patient that 7 days before the breath test, he or she should stop taking antibiotics, bismuth-containing medication (Pepto-Bismol), and proton pump inhibitor medication, such as omeprazole (Prilosec), lansoprazole (Prevacid), esomeprazole (Nexium), or rabeprazole (Aciphex).
Hematocrit
Also called: (Hct); Microhematocrit
Purpose of the test
The hematocrit is useful in the evaluation of blood loss, anemia, hemolytic anemia, polycythemia, and dehydration.
Basics the nurse needs to know
The hematocrit is a measurement of the proportion of whole blood volume occupied by erythrocytes. The value is expressed as a percentage or fraction of cells to whole blood. For example, a hematocrit value of 40% means that there are 40 mL of erythrocytes in 1 dL of blood.
Decreased values
The hematocrit falls to less than the reference value when an excessive loss of erythrocytes occurs, as in hemolytic anemia or after excessive bleeding. It also can occur because fewer red blood cells are made or the erythrocytes are microcytic (smaller). The hematocrit also can decrease because of excessive intravenous fluids or fluid retention that creates greater plasma volume. The fluids exert a dilution effect, meaning that normal numbers of red blood cells are in a larger amount of fluid. In bleeding or hemorrhage, the hematocrit drops several hours after the bleeding episode. The severity of the drop in value correlates directly with the amount of red blood cells that are lost.
Interfering factors
NURSING CARE
Pretest
Nursing actions are similar to those used in other venipuncture or fingerstick procedures (see Chapter 2), with the following additional measures.
Posttest
Elevated hematocrit
When the patient’s condition is due to dehydration and the hematocrit is elevated, fluid and electrolyte replacement is usually administered intravenously, as prescribed. The nurse ensures that the correct solution and the correct amount of solution are given in the prescribed period. If the patient’s medical condition allows, the nurse encourages the patient to take extra fluids orally. As the patient is rehydrated, the hematocrit value will fall toward the normal value.
Decreased hematocrit
When the patient is hemorrhaging or has just had a severe bleeding episode, the hematocrit value decreases. After transfusion replacement of packed cells or whole blood, the nurse monitors the hematocrit results for a rising value. The hematocrit value, however, is not reliable immediately after an acute blood loss or blood transfusion. The changes will occur a few hours later.
Nursing response to critical values
When the hematocrit rises to a critical value or higher, the patient is at great risk of developing a myocardial infarction or a stroke because of increased viscosity. Those who are most vulnerable are patients with preexisting cardiovascular disease. When the hematocrit decreases to a critical value or lower, the patient may go into shock, particularly when there is associated blood loss or hemorrhage. The nurse notifies the physician immediately of a hematocrit result that is in the critical value range.
The nurse also starts frequent and regular monitoring of vital signs and assessment of the patient’s overall condition. The patient may complain of intense chest pain or exhibit signs of neurologic abnormality, including loss of consciousness, aphasia (impairment or loss of speech), hemiparesis (weakness in one side of the body), and hemiplegia (paralysis on one side of the body).
Hemoglobin
Purpose of the test
The hemoglobin is used to measure the severity of anemia or polycythemia, and it monitors the response to treatment of anemia. It is also used to calculate the mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) values.
Basics the nurse needs to know
Hemoglobin is the oxygen-carrying compound contained in each erythrocyte. The large amount of hemoglobin and the broad surface area of each erythrocyte enable the red blood cells to have a large oxygen-carrying capacity and to function with great efficiency.
Elevated values
An elevated hemoglobin value may be a result of either excess production of erythrocytes by the bone marrow or dehydration. In excess production of erythrocytes, the hemoglobin rises because it is present in additional cells. In dehydration, the red blood cell counts and hemoglobin are relatively high because of the normal number and quality of cells that are concentrated in a smaller amount of fluid.
Decreased values
An individual generally is considered anemic when the hemoglobin value for the male is less than 13 g/dL (SI: <130 g/L) and for the female, less than 11 g/dL (SI: <110 g/L). The low hemoglobin value can be caused by a low red blood cell count, by a lack of hemoglobin in each erythrocyte, or by fluid retention. The low red cell count may be a lack of production by the bone marrow, a loss of red blood cells in bleeding, or a loss of red blood cells from hemolysis (rapid destruction of the erythrocytes). The lack of hemoglobin in the erythrocytes is often due to a lack of iron, an essential mineral used to make heme, the iron-containing molecule of hemoglobin. In fluid retention, red blood cell counts and hemoglobin values are normal, but the cells are diluted in a greater amount of fluid.
Interfering factors
NURSING CARE
Nursing actions are similar to those used in other venipuncture or capillary puncture procedures (see Chapter 2), with the following additional measures.
Pretest
Posttest
Nursing response to critical values
The nurse notifies the physician of a severe decrease in the reference value. The decrease in hemoglobin means that less oxygen can be transported. The lungs and heart must work harder to get as much oxygen to cells as possible. As a result, both the pulse and respiratory rate will increase.
Hemoglobin electrophoresis
Purpose of the test
Hemoglobin electrophoresis is used to detect hemoglobinopathy (a genetic disorder of hemoglobin) and identify the type of anemia that results from the abnormal hemoglobin. It is also one of the tests used to identify sickle cell hemoglobin and differentiate between sickle cell trait and disease.
Basics the nurse needs to know
In the body, the manufacture of the various types of globin that bind with iron to make hemoglobin is genetically determined. The specific gene clusters to make alpha-type globins are located on chromosome 16 and the cluster of genes to make beta-type globins are located on chromosome 11. Mutations or absence of some of these genes will result in altered production or function of hemoglobin in the red blood cells of the affected individual. The genetic mutation of one or more genes can be transmitted to the offspring of the individual in an autosomal recessive inheritance pattern.
In the normal adult, the three types of hemoglobin found in erythrocytes are HbA, HbA2, and HbF. Using the electrophoresis method, the test separates the normal from the abnormal hemoglobin types and measures the percentage amounts of each type.
There are more than 700 variants (abnormal or altered types) of hemoglobin, identified by letters other than HbA, HbA2, and HbF. Hemoglobinopathy is the general term used to describe altered hemoglobin and some forms of hemolytic anemia. The specific hemoglobinopathy affects either the structure of the hemoglobin molecules or causes a decreased synthesis of hemoglobin, as in the various thalassemias. Of all the abnormal variants, HbS, or sickle cell hemoglobin, is the most predominant. Another common variant is HbC. Some conditions are asymptomatic or mild because the genetic defect of hemoglobin is a heterozygous (mixed) type, or trait condition. In the heterozogous (trait) condition, the mutant gene is inherited from one, but not both parents. In the homozygous (pure) state that produces the disease, the individual inherits the mutant gene from both parents.
Hemoglobin A2
Although this is normal hemoglobin, it is only a small proportion of the total hemoglobin in healthy individuals. Hemoglobin electrophoresis evaluates the amount of HbA2 in the investigation of β-thalassemia trait and differentiates β-thalassemia diseases from iron deficiency anemia. The β-thalassemia diseases are a group of disorders that produce a range of conditions varying from no clinical change to severe hypochromic, microcytic anemia. The amount of HbA2 is increased in the β-thalassemia trait. Abnormal elevations of HbA2 may include up to 7% of the total hemoglobin content.
Hemoglobin F
HbF is the hemoglobin present in fetal life. During infancy and early childhood, it is gradually replaced by HbA and HbA2. By age 3, only 2% or less of HbF remains and the rest of the hemoglobin is HbA and HbA2. Adults can have abnormal quantities of HbF in a condition called hereditary persistence of fetal hemoglobin. The homozygous state produces mildly microcytic, hypochromic erythrocytes without anemia. The hemoglobin electrophoresis test reveals 100% HbF. The heterozygous state does not cause anemia, but hemoglobin electrophoresis reveals 30% to 40% HbF.
Hemoglobin S
In the homozygous state, HbS produces the disease of sickle cell anemia, a type of severe hemolytic anemia that causes many health problems throughout life. In the heterozygous form, or sickle cell trait, hemoglobin electrophoresis demonstrates 30% to 35% HbS. Sickle cell trait produces no disease or hematologic abnormality unless the person experiences hypoxia, acidosis, or thrombosis (a blood clot).
Hemoglobin C
In the homozygous state of HbC disease, a mild hemolytic anemia often exists, but it is usually asymptomatic. On electrophoresis, no HbA is present. Most of the hemoglobin is HbC, with smaller quantities of other forms of hemoglobin. In the heterozygous state, 30% to 40% of the hemoglobin is type HbC.
Interfering factors
NURSING CARE
Nursing actions are similar to those used in other venipuncture or finger stick procedures (see Chapter 2), with the following additional measures.
Posttest
Health promotion
In all states of the U.S. and its territories, screening for sickle cell disease is mandated for all newborns, regardless of ethnicity (US Preventive Services Task Force, 2007).
Hemosiderin, urinary
Purpose of the test
Urinary hemosiderin is used to identify hemolytic anemia that is associated with hemolysis of red blood cells.
Basics the nurse needs to know
Hemosiderin granules are indicators of hemoglobin in the urine resulting from significant acute or chronic intravascular hemolysis. With the lysis of many erythrocytes, free hemoglobin is converted to ferritin and hemosiderin by the kidneys. The kidneys then remove the hemosiderin and those granules are present in the cells or casts in urinary sediment. The hemosiderin appears in the urine on the second or third day after the hemolytic episode. Urinary hemosiderin may also be caused by the excretion of excess iron, as from hematochromatosis.
The presence of hemosiderin in urine may not be detected by a urine reagent strip. In the laboratory analysis, however, the urinary sediment is stained with Prussian blue stain. If hemosiderin is present, the iron in urinary hemosiderin appears as blue-stained granules. The results are seen by microscopic examination of the slides that contain urinary cells and casts.
How the test is done
A random sample of 30 to 60 mL of urine is collected in a clean container with a lid.
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