H | Nurse Key

Haptoglobin

Specimen or type of test:

NURSING CARE

Nursing actions are similar to those used in other venipuncture procedures (see Chapter 2), with the following additional measures.

Pretest

• This test may be used to monitor for a blood transfusion reaction. If prescribed, ensure that the haptoglobin specimen is drawn before starting the transfusion. A repeat test may be ordered at the conclusion of the transfusion.

Posttest

• The nurse compares the current results with the patient’s baseline value to monitor for the level and direction of change. The physician is notified of a sudden or severe decrease in this laboratory value. The cause of an abnormal laboratory value will determine the interventions that are needed.

• The nurse should assess any fresh sample of urine for change in color. If the haptoglobin level is decreased, free hemoglobin will be filtered out of the blood into the urine. Hemoglobin changes the color of the urine to dark red or brown.

Helicobacter pylori tests

Specimen or type of test:

Blood, Breath, Feces, Gastric Biopsy

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.

H. pylori antigen test

The antigen of H. pylori can be detected in the fecal matter of the infected patient. It can also be used to evaluate the patient’s response to treatment. After treatment, a negative test result confirms that the infection has been eradicated.

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.

Rapid urease test.

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.

PCR-DNA.

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.

Significance of test results

Positive values

H. pylori infection

Chronic gastritis

Peptic ulcer disease

Gastric cancer

Interfering factors

• Recent antimicrobial therapy

• Current bismuth preparation

• Current proton pump inhibitor medication

NURSING CARE

Pretest

• Serology antibody. Nursing actions are similar to those used in other venipuncture procedures (see Chapter 2), with the following additional measures.

• Breath test. Inform the client that a small amount of low-dose radiation will be in the capsule, but it will be exhaled within hours and the brief exposure will not harm the patient.

Posttest

After treatment with antibiotics, follow-up testing for H. pylori antigen in the feces may be done to verify that the infection has been eradicated. This testing should occur no sooner than 4 weeks post treatment.

Hematocrit

Also called: (Hct); Microhematocrit

Specimen or type of test:

Blood

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.

Elevated values

The hematocrit rises if the number or size of the erythrocytes increases or when the plasma fluid volume is reduced. When the fluid volume is decreased, the red blood cells become concentrated in the smaller fluid volume. The blood is thicker or has increased viscosity.

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.

How the test is done

Venipuncture or skin puncture is done to collect a sample of blood.

Interfering factors

• None

NURSING CARE

Pretest

Nursing actions are similar to those used in other venipuncture or fingerstick procedures (see Chapter 2), with the following additional measures.

• The nurse informs the patient that blood will be drawn at intervals to monitor his or her condition.

During the test

• Ensure that the blood sample is not taken from a vein in the hand or arm with an intravenous line. Hemodilution with intravenous fluids will lower the hematocrit value falsely.

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.

• Because the loss of blood or fluids often results in hemodynamic instability, the nurse measures and records vital signs at regular and frequent intervals. Abnormal findings would include hypotension (a low blood pressure), tachycardia (a rapid pulse), and dyspnea (labored breathing).

• When the patient has excess fluid volume, often with edema, the underlying cause must be diagnosed and treated medically. In cases such as cirrhosis, congestive heart failure, and renal failure, the hematocrit falls because the normal number of red blood cells is diluted in excess plasma. The nurse carries out the medical treatment protocol that often includes medications, fluid restrictions, and salt restrictions. As excess fluid is excreted, the hematocrit rises toward a more normal reference value.

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

Also called: Hgb, Hb

Specimen or type of test:

Whole Blood

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.

How the test is done

Venipuncture or capillary puncture is used to obtain a sample of blood

Interfering factors

• White blood cell count greater than 100 × 10³ μL (SI: >100 × 10⁹/L)

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

• The nurse informs the patient of the need for additional lab testing to monitor his or her condition. When the patient had a severe bleeding episode, the hemoglobin measurement is taken at regular intervals. The decreased results indicate the severity of the blood loss. Likewise, after transfusion replacement of packed cells or whole blood, this test is used to monitor for a rise in the value. Ensure that the tests are performed at the indicated times.

During the test

• Ensure that the blood sample is not taken from the arm that has an intravenous line in place. The intravenous infusion would dilute the blood and alter the test value.

Posttest

• When the hemoglobin level is decreased, the nurse can assess abnormal physical responses that include dizziness, pallor, and fatigue associated with physical activity. When the decline in hemoglobin occurs slowly over time, the patient may not experience symptoms of anemia, particularly when resting. With physical activity, however, the patient may report breathlessness or palpitations.

• There are numerous causes for an abnormal hemoglobin value. Laboratory testing will be needed to determine the specific cause and appropriate medical therapy. Additional specific nursing interventions will be implemented when the medical diagnosis is made.

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

Specimen or type of test:

Blood

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).

How the test is done

Venipuncture or capillary puncture is used to collect a sample of blood.

Interfering factors

• Blood transfusion in the preceding 4 months

• Hemolysis of the erythrocytes

NURSING CARE

Nursing actions are similar to those used in other venipuncture or finger stick procedures (see Chapter 2), with the following additional measures.

Pretest

• Ask the patient about any transfusion of blood received within the preceding 4 months. A recent transfusion would make the findings of the test inconsistent.

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).

• The genetic counselor and the physician discuss the abnormal results with the parents of the infant, providing counseling and education

• The nurse also provides support to the parents who have an infant who tested positive for sickle cell trait or disease. Parents may not understand the difference between trait and disease. The parents often have feelings of concern, guilt, fear, and worry about the well-being of the infant. In discharge planning, encourage the parents to keep the follow-up appointments with the pediatrician for additional testing and specific follow-up care for the infant.

• When one child of the family tests positive for the trait or disease, the nurse encourages testing of all members of the family. If the individual knows his or her genetic status regarding this mutation, he or she can make informed decisions regarding health and reproduction.

Hemosiderin, urinary

Specimen or type of test:

Urine

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.

REFERENCE VALUES

Negative

How the test is done

A random sample of 30 to 60 mL of urine is collected in a clean container with a lid.

Significance of test results

Positive values

Blood transfusion reaction

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