I

Immunoglobin E antibody

Also called: IgE antibody test, (IgE)

Specimen or type of test:

Serum

Purpose of the test

This test measures the amount of IgE antibody in the blood and the identification of the specific antigen(s) that caused the IgE level to rise. The test identifies sensitivity to one or more specific antigens and confirms or excludes allergy as the cause of the patient’s symptoms.

Basics the nurse needs to know

There are many sources of allergy in the home and environment that have the potential to cause an allergic response in sensitized individuals. Common allergens are foods, pollens, mold spores, dust mites, animal dander and proteins, insect bites, parasites, and particular medications (see box 4 on p. 59).

Immunoglobin E is the allergy antibody. The IgE antibodies in nonallergic individuals exist at very low levels in the blood. If, however, the individual is allergic to a particular substance and is exposed to it, the IgE antibody level usually rises in the blood, demonstrating sensitivity to the allergen.

The allergen-specific IgE antibody test method uses in vitro testing to identify offending allergens for the individual patient. This means that a blood sample is drawn and in the laboratory specific allergens are mixed with the serum sample to measure the IgE response. The IgE testing is the newer and more accurate method of testing.

The radioallergosorbent test (RAST) method is no longer used, but the term RAST has continued in use as a general name for IgE antibody testing. To avoid confusion, the RAST colloquialism for IgE testing should be discontinued (Cox, Williams, Sicherer, 2008).

If additional testing is needed to identify specific allergens that cause a positive response in sensitized patients, the skin prick, intradermal injection, or patch test methods testing may be done. (See Allergy testing, p. 58 and Patch Test, Skin, p. 480).

REFERENCE VALUES

IgE Antibody (fluorescent enzyme immunoassay method): <0.35-100 kU/L

Note: there are three different manufacturers of the testing materials and the normal values and test results are based on which product was used.

How the test is done

Venipuncture is used to collect a specimen of blood.

Significance of test results

Elevated values

Sensitivity to specific allergens

Interfering factors

• None

NURSING CARE

Pretest

• A complete clinical history and physical examination must be done to help identify possible allergens, recent exposure or contact with these allergens, and the type of physical symptoms that resulted. The patient’s age, occupation, hobbies, and employment are also noted.

•   Patient teaching

• Instruct the patient to continue taking the antihistamine or corticosteroid medications as prescribed. Current use will not interfere with this blood test.

• Reassure the patient that the test is safe and will not worsen the current symptoms.

Posttest

• If the patient has tested positive to specific IgE antibodies and the clinical history and physical examination also indicates exposure to the allergen, additional skin testing methods may be employed to confirm the medical diagnosis. Once the allergy is confirmed and the specific allergen is identified, the goals of treatment for the patient will be to avoid future contact or exposure to the allergen; use prescribed medications to lessen the symptoms of the allergic response.

Impedance cardiography

See Catheterization, Cardiac on p. 221.

Influenza tests

Includes: Influenza A, Influenza B, H1N1

Purpose of the test

The testing identifies influenza A and B viruses and differentiates them from other causes of acute respiratory infections. The results help with the diagnosis and provide guidance for medical treatment.

Specimen or type of test:

Nasal secretions

Basics the nurse needs to know

The influenza viruses A and B cause worldwide acute respiratory infection in seasonal patterns. In North America the flu season occurs from November to April. H1N1 is one subtype of the influenza A virus. The influenza A virus mutates every year and result in outbreaks of the flu annually. The influenza B virus mutates less frequently and outbreaks occur every few years. The method of transmission from person to person is by respiratory droplet and probable hand contact with contaminated objects such as doorknobs.

These viruses initially infect various animals, birds, or mammals, such as pigs or chickens. As the virus gradually adapts and mutates, it becomes transmissible to humans. Because humans have no resistance to the mutant strain, outbreaks occur quickly and spread in epidemic and pandemic patterns of illness.

The influenza virus has an envelope that surrounds the core genetic material. The envelope contains various H and N type antigens. As the RNA of the influenza A virus mutates, it changes the structure of the H and N antigens and a new strain of the virus occurs. The outbreak of the flu of 2009-2011 is a type A H1N1 influenza infection (Mahon, Lehman & Manuselis, 2011).

Patients with the flu have high fever, a nonproductive cough, and muscle aches. The complication of pneumonia can develop and death can occur. Pregnant women are very vulnerable to severe illness and complication with this current strain of A/H1N1 influenza. Morbidly obese people may also have a high risk of complications.

Laboratory testing detects the type A and B types of influenza, but at this time there is no test for the subgroup of H1N1. The rapid tests are most accurate during the busiest part of the flu season and are least accurate at the beginning and end of the flu season. Not every patient is tested.

There are various methods to identify the virus and most can distinguish between type A and type B. Some of the tests are not practical in the clinical setting because of the lengthy delay before the results are known. For example, viral culture takes 5 to 10 days to obtain the results and reverse transcriptase-PCR method takes 1 to 2 days to complete the testing. In this discussion, only the tests that are most useful are included. The antibody test results are available in 2 to 4 hours and the results of rapid tests are available in 15 minutes or less (Lewandewski, 2009c).

REFERENCE VALUES

Direct fluorescent antibody (DFA): negative

Enzyme immunosorbent antibody (EIA): negative

Rapid tests: negative

How the test is done

The best method is to collect samples of nasal secretions or nasal washings by swab or aspiration. Throat swabbing or bronchial washings may also be obtained.

Significance of the test results

Positive values

Influenza A or B

Interfering factors

• Use of a generic swab that is not part of the test kit.

NURSING CARE

Pretest

All nurses and employees who give patient care should be vaccinated before the start of every flu season. When flu is suspected, the nurse wears a mask and asks the patient to wear one also. The nurse monitors the vital signs including blood pressure, pulse, respirations, and temperature. The patient’s history and the results of the physical examination provide important information for the diagnosis. The results are recorded in the patient’s record.

Posttest

•   Patient teaching.

If the patient has the flu, the nurse teaches the patient, family, and caregiver to wash their hands frequently. Respiratory etiquette is reinforced. In the home, washing of dirty dishes and utensils should be done promptly. The patient’s bed linens need to be changed often and the dirty linens washed.

Health promotion

The nurse teaches that everyone older than 6 months should have the flu vaccine, annually.

Insulin

Also called: Immunoreactive Insulin

Specimen or type of test:

Serum, plasma

Purpose of the test

Insulin levels are determined to assess for insulin-producing tumors, to confirm suspected insulin-resistant states, and as part of the evaluation of glucocorticoid insufficiency. It is not recommended for routine testing of patients with diabetes mellitus.

Basics the nurse needs to know

Insulin is a protein hormone produced and secreted by the pancreas. It has a short half-life (3 to 5 minutes) and is broken down by the liver and kidneys. Insulin is secreted in response to food intake. It increases in concentration within 10 minutes of eating, peaks in 30 to 45 minutes, and returns to baseline levels within 90 to 120 minutes. Normally, insulin levels increase as blood glucose levels increase.

Without insulin, carbohydrate, protein, and fat metabolism are affected, resulting in hyperglycemia and metabolic acidosis.

REFERENCE VALUES

Fasting

Newborn: 3-20 μU/mL or SI: 21-139 pmol/L

Adult: 5-25 μU/mL or SI: 35-174 pmol/L

1 hour after eating

50-130 μU/mL or SI: 347.3-902.8 pmol/L

2 hours after eating

<30 μU/mL or SI: <208.4 pmol/L

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