Tuberculosis: Skin and Blood Tests

Common use

Specimen

Normal findings

Description

This procedure is contraindicated for

N/A

Indications

• Evaluate cough, weight loss, fatigue, hemoptysis, and abnormal x-rays to determine if the cause of symptoms is TB
• Evaluate known or suspected exposure to TB, with or without symptoms, to determine if TB is present
• Evaluate patients with medical conditions placing them at risk for TB (e.g., AIDS, lymphoma, diabetes)
• Screen populations at risk for developing TB (e.g., health-care providers [HCPs], nursing home residents, correctional facility personnel, prison inmates, and residents of the inner city living in poor hygienic conditions)

Potential diagnosis

Positive findings in:

• Pulmonary TB

Critical findings

• Positive results

• It is essential that a critical finding be communicated immediately to the requesting health-care provider (HCP). A listing of these findings varies among facilities.

• Timely notification of a critical finding for lab or diagnostic studies is a role expectation of the professional nurse. Notification processes will vary among facilities. Upon receipt of the critical value the information should be read back to the caller to verify accuracy. Most policies require immediate notification of the primary HCP, Hospitalist, or on-call HCP. Reported information includes the patient’s name, unique identifiers, critical value, name of the person giving the report, and name of the person receiving the report. Documentation of notification should be made in the medical record with the name of the HCP notified, time and date of notification, and any orders received. Any delay in a timely report of a critical finding may require completion of a notification form with review by Risk Management.

Interfering factors

General

• Each of the blood and skin tests evaluate different facets of the immune response and use different methodologies and reagents; interpretations may not be interchangeable.

Skin Test

• Drugs such as immunosuppressive agents or steroids can alter results.
• Diseases such as hematological cancers or sarcoidosis can alter results.
• Recent or present bacterial, fungal, or viral infections may affect results. False-positive results may be caused by the presence of nontuberculous mycobacteria or by serial testing.
• False-negative results can occur if sensitized T cells are temporarily decreased. False-negative results also can occur in the presence of bacterial infections, immunological deficiencies, immunosuppressive agents, live-virus vaccinations (e.g., measles, mumps, varicella, rubella), malnutrition, old age, overwhelming TB, renal failure, and active viral infections (e.g., chickenpox, measles, mumps).
• Improper storage of the tuberculin solution (e.g., with respect to temperature, exposure to light, and stability on opening) may affect the results.
• Improper technique when performing the intradermal injection (e.g., injecting into subcutaneous tissue) may cause false-negative results.
• Incorrect amount or dilution of antigen injected or delayed injection after drawing the antigen up into the syringe may affect the results.
• Incorrect reading of the measurement of response or timing of the reading may interfere with results.
• It is not known whether the test has teratogenic effects or reproductive implications; the test should be administered to pregnant women only when clearly indicated.
• The test should not be administered to a patient with a previously positive tuberculin skin test because of the danger of severe reaction, including vesiculation, ulceration, and necrosis.
• The test does not distinguish between current and past infection.

Blood Test

• The performance of these blood tests has not been evaluated in large studies with patients who have impaired or altered immune function, have or are highly likely to develop TB, are younger than 17, are pregnant, or have diseases other than TB. These individuals are either immunosuppressed, immunocompromised, or have immature immune function and may not produce sufficient numbers of T lymphocytes for accurate results. The testing laboratory should be consulted for interpretation of results or limitations for use with patients in these categories.
• False-negative results are possible due to exposure or infection prior to development of detectable immune response.
• False-positive results are possible due to some cross-reactivity to some strains of environmental mycobacteria.
• False-negative results are possible due to exposure or infection prior to development of detectable immune response.

Nursing Implications and Procedure

Potential nursing problems

Pretest

Blood and Skin Tests

• Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
• Patient Teaching: Inform the patient this test can assess for a tuberculin infection or exposure.
• Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies and sensitivities to latex.
• Obtain a history of the patient’s immune and respiratory systems, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures. Obtain a history of TB or TB exposure, signs and symptoms indicating possible TB, and other skin tests or vaccinations and sensitivities.
• Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
• Review the procedure with the patient.

Skin Test

• Before beginning the test, ensure that the patient does not currently have TB and has not previously had a positive skin test. Do not administer the test if the patient has a skin rash or other eruptions at the test site. Inform the patient that the procedure takes approximately 5 min. Address concerns about pain and explain that a moderate amount of pain may be experienced when the intradermal injection is performed.
• Emphasize to the patient that the area should not be scratched or disturbed after the injection and before the reading.

Blood Test

• Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.

Blood and Skin Tests

• Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
• Note that there are no food, fluid, or medication restrictions unless by medical direction.

Intratest

• Potential complications: N/A
• Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient.

Blood and Skin Tests

• Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
• Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.

Skin Test

• Have epinephrine hydrochloride solution (1:1,000) available in the event of anaphylaxis.
• Cleanse the skin site on the lower anterior forearm with alcohol swabs and allow to air-dry.

Multipuncture Test

• Remove the cap covering the tines and stretch the forearm skin taut. Firmly press the device into the prepared site, hold it in place for 1 sec, and then remove it. Four punctures should be visible. Record the site, and remind the patient to return in 48 to 72 hr to have the test read. At the time of the reading, use a plastic ruler to measure the diameter of the largest indurated area, making sure the room is sufficiently lighted to perform the reading. A palpable induration greater than or equal to 2 mm at one or more of the punctures indicates a positive test result.

Mantoux (Intradermal) Test

• Prepare PPD or old tuberculin in a tuberculin syringe with a short, 26-gauge needle attached. Prepare the appropriate dilution and amount for the most commonly used intermediate strength (5 tuberculin units in 0.1 mL) or a first strength usually used for children (1 tuberculin unit in 0.1 mL). Inject the preparation intradermally at the prepared site as soon as it is drawn up into the syringe. When properly injected, a bleb or wheal 6 to 10 mm in diameter is formed within the layers of the skin. Record the site, and remind the patient to return in 48 to 72 hr to have the test read. At the time of the reading, use a plastic ruler to measure the diameter of the largest indurated area, making sure the room is sufficiently lighted to perform the reading. Palpate for thickening of the tissue; a positive result is indicated by a reaction of 5 mm or more with erythema and edema.

Blood Test

• Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
• Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
• Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

• Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
• Recognize anxiety related to test results and be supportive of perceived loss of independence and fear of shortened life expectancy. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate. Counsel the patient, as appropriate, regarding the risk of transmission and proper prophylaxis, and reinforce the importance of strict adherence to the treatment regimen. Inform the patient that positive findings must be reported to local health department officials, who will question him or her regarding other persons who may have been exposed through contact. Educate the patient regarding access to counseling services.
• Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

• Patient Education

  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP.
  • Emphasize to the patient who receives skin testing the need to return and have the test results read within the specified time frame of 48 to 72 hr after injection.
  • Inform the patient that the effects from a positive response at the site can remain for 1 wk.
  • Educate the patient that a positive result may put him or her at risk for infection related to impaired primary defenses, impaired gas exchange related to decrease in effective lung surface, and intolerance to activity related to an imbalance between oxygen supply and demand.
  • Answer any questions or address any concerns voiced by the patient or family.

• Expected Patient Outcomes

  • Knowledge
  • States understanding of the importance of covering the mouth during coughing or sneezing to decrease possibility of droplet contamination
  • States understanding of the importance of an adequate fluid intake to liquefy secretions
  • Skills
  • Demonstrates the correct technique for covering the mouth and nose when coughing or sneezing
  • Demonstrates proficient cough and deep breathing
  • Attitude
  • Complies with the request to refrain from smoking
  • Complies with the recommendation to take prescribed medication as ordered

Related Monographs

• Related tests include alveolar/arterial gradient, angiography pulmonary, biopsy lung, blood gases, broncho-scopy, calcium, carbon dioxide, chest x-ray, CBC WBC count and differential, CT thoracic, culture and smear mycobacteria, culture blood, culture sputum, cytology sputum, eosinophil count, ESR, gallium scan, Gram stain, lung perfusion scan, lung ventilation scan, mediastinoscopy, pleural fluid analysis, PFT, and zinc.
• Refer to the Immune and Respiratory systems tables at the end of the book for related tests by body system.