Contact Assessment

Contact Assessment and Tuberculosis Skin Testing (TST)

Disclosure of Potential for

Conflict of Interest

M. Ruth Deane RN BNCommunicable Disease CoordinatorFINANCIAL DISCLOSUREGrants/Research Support: noneSpeakers Bureau/Honoraria:

noneConsulting Fees: none

Tuberculosis (TB) contact investigations are undertaken to evaluate and follow-up close contacts of active cases, in order to identify secondary cases with active disease, and to identify and treat those with latent tuberculosis infection (LTBI).

Purpose of the TB Investigations

Assessment of a Contact

Symptom review• The following questions

should be asked:- Do you have a cough right now? Has

this cough lasted longer than three weeks?

- Have you coughed up any blood?- Have you lost any weight? Were you

trying to loose weight?- Do you have any fever?

Assessment of a contact con’t

- Do you have night sweats? If yes, is there a known cause? (I.e. menopause, note as a symptom and also note the attributable cause)

- Do you have any pain with breathing?- Are you fatigued?

If any symptom was present, but has since completely resolved, mark as ‘absent’ but with a brief note regarding when they occurred and how long they lasted.

Referral for Sputum

Any contact with a cough lasting three weeks or longer

Should advise those without a cough, but with other symptoms of TB, that we may send for induced sputum based on CXR results

Referral for sputum con’t

Need to provide specimen containers and instructions

Need three samples, at least one should be early morning

Need to be refrigerated until delivered to the laboratory

TB History

Have you ever had TB? • Need documented history of

fully treated disease

Have you ever had a Tuberculin Skin Test?• Need documented result, if

not documented, repeat

High risk conditions when

associated with TB contact

HIV***AIDS***Transplantation (related to

immunosuppressant therapy)SilicosisChronic renal failure requiring

hemodialysis

Hi Risk Conditions Cont

Carcinoma of the head and neckRecent TB infection (< 2 years) Abnormal chest x-ray

fibronodular diseaseTreatment with glucocoriticoids

Increased risk conditions

Tumor necrosis factor alpha (TNF) antagonists• infliximab (Remicade)• etanercept (Enbrel)• adalimumab (Humira)

Increased risk conditions

Diabetes mellitusUnderweight <90% ideal body

weightYoung age when infected(0-4yrs)Cigarette smokerAbnormal chest x-ray -

granuloma

The tuberculin skin test

Different types of tuberculin tests are available

The Mantoux (intradermal) tuberculin skin test is the preferred type because it is the most accurate

The tuberculin used in the skin test is also known a s Purified protein derivative or “PPD”

Storage and handling of Tuberculin

• Date and initial when vial is opened• Discard 30 days after opening• It is sensitive to light, keep out of

light• Draw up just prior to injection• Store at 2 to 8 degrees C° in a

refrigerator or cooler with ice packs

Contraindications

Do not test people who:• Have a documented TST result > 10 mm• Have had TB disease in the past,

confirmed • Have had severe blistering TST reactions

in the past• Have severe eczema• Have a history of anaphylactic reaction to

past TST

Common Side Effects

• Pain• itchiness • discomfort at the test site may

occurTreat with cool cloths or ice. Do

not scratch.

Severe side effects

• Blistering• Ulcers• Necrosis• Scarring from strongly positive

reactions• Anaphylactic reaction

Dosage and Administration

Site: • Left inner aspect of the forearm 2-4

inches below the elbow. • Avoid areas with abrasions, swelling,

visible veins or lesions that will make TST results difficult to interpret.

• Cleanse skin with alcohol swab and allow to dry

Dosage and Administration

Dose:0.1 ml of 5 TU (Tuberculin Units) of

Tuberculin Purified Protein Derivative (Mantoux)

Manufactured by Aventis Pasteur, trade name Tubersol

Supplied by Manitoba TB Control Program for contact testing and select screening programs only

Dosage and Administration

Route: • Intradermally with a 27 gauge, ½

inch needle and 1ml syringe.• Hold skin of the forearm tautly.• Insert needle with bevel up at a 10-

15 degree angle just until the bevel disappears under the skin.

Dosage and Administration

• Slowly inject 0.1 ml Tubersol until activation of safety mechanism

• Look for a discrete, pale elevation of the skin (wheal)

• Wheal should measure 6-10 mm in diameter

• Do not massage the site or cover site with a bandage

Dosage and Administration

If solution leaks from the site or no wheal appears:

• TST will be inaccurate• Repeat injection at least two

inches from the first TST or on the other forearm

Timing of administration

“TST conversion occurs within 8 weeks of exposure and infection. The traditional concept was that conversion occurred in up to 12 weeks. However, all available experimental and epidemiologic evidence consistently shows that this interval is less than 8 weeks.” CTS p 67

How is the skin test read?

Test is read by a trained health worker 48 - 72 hours after the tuberculin injection

Read the TST in good light (may want to bring a pen light) with the forearm supported on a firm surface and the elbow slightly flexed.

Reposition as necessary if interpretation is difficult

How is the skin test read?

Diameter of the indurated (swelling) area is measured across the forearm

Erythema (redness) is not measured

Test result is measured in millimeters (mm)

How is the skin test read?

Find induration by looking at site from the side and then by direct palpation. Mark edges of induration with a pen

Also, using a ballpoint pen, draw a line from the outer edge of the arm inward toward the induration, and stop when the pen comes against the border, repeat from the other side

Only the induration is being measured.

This is CORRECT.

The erythema is being measured. This is INCORRECT.

Routine Practices for TST reading

Wash hands with waterless hand gel or water between clients

Cleanse ruler with alcohol swab between readings

Ensure ‘cover your cough’ policy is enforced

What makes the reaction

significant?

Whether a reaction to the TST is classified as significant, depends on the size of the induration (swelling) and the person’s risk factors for TB

Definition of a significant

(positive)TST

0-4 mm HIV infection with immune suppression and the expected likelihood of TB infection is high (e.g. close contact; abnormal x-ray)

Definition of a significant

(positive)TST

>5 or more millimeters (mm)• Contact to an infectious case of TB• Immunocompromised persons

including HIV infection• Person with an abnormal chest

radiograph, but no evidence of active TB

Definition of a significant

(positive)TST

> 10 or more millimeters (mm)• All other persons

Recording TST results

Record the size of the induration in millimeters

Don’t write ‘negative’ or ‘neg’ but record as 0 mm

Don’t write ‘positive’ or ‘pos’, but record the actual measurement

Factors that can cause a false

positive reading

• Infection with non-tuberculosis mycobacterium

• Vaccination with BCG• Allergic reaction to bandage/tape

used to cover TST • Improper administration of TST• Failure to measure induration

correctly

BCG can be ignored as cause of false

positive if:

• Was given in infancy and the person tested is now 10 years or older

• There is a high probability of TB infection (close contact; high risk community or country of origin)

• There is a high risk of progression from infection to disease

BCG should be considered likely

cause of a positive TST if:

• Was given after 12 months of age AND the person is either Canadian – born non Aboriginal OR an immigrant /visitor from a low TB incidence country.

BCG Scar

Presence of scar indicates that the vaccination ‘took’ or was effective and should be documented.

BCG is administered on the left (usually) shoulder in Manitoba

Other sites include the leg and backSmallpox vaccination last given in 1970 in

Manitoba. No documentation found for other countries

Factors that can cause a false

negative reading• Immune suppression due to:

• Advanced age• Treatment with corticosteroids• Cancer therapy agents• HIV infection• Possible tumor necrosis alfa inhibitors• Malnutrition• Severe illness, including active TB• Major viral illness or immunization within 4 weeks

with MMR, varicella or yellow fever vaccine• Very young age (less than six months)

False negative continued

Technique:• Improper storage• Adsorption• Poor injection technique • Failure to detect/interpret

induration

What is a “boosted” reaction

to a TST

Some persons infected with TB in the past lose their ability to react quickly to TST

A first TB test may be (falsely) negative Another test, one week or more later

(up to one year) will show a (true) positive reaction.

Why do we not do a ‘two-step” in

contact investigations?

In contact investigations, the ‘contact’ (I.e. breathing in the TB bacilli) is the ‘first step’. Therefore only one TST is needed to identify past infection.

Why do we not do a ‘two-step” in

contact investigations?

Two TSTs are done in some investigations based on time since last contact, ie need at least 8 weeks to develop a reaction.

Some of the contacts who are positive on the second test, will be due to a boosted reaction.

Referral for assessment and treatment of LTBI is necessary regardless

So what does a ‘significant’

reaction mean?

We must assume, in the absence of a more definitive test, that a significant reaction indicates tuberculosis infection.

In the absence of a documented <10mm two step baseline with in the last year, we will not know when this infection occurred.

So what does a ‘significant’

reaction mean?

Approximately 5% of immunocompetent newly infected persons will develop primary or progressive primary disease within 18 – 24 months. Those who do not develop primary disease have a 5% chance of reactivation or post primary TB at some time in their lives.

Referral for CXR

• Contacts with significant reactions• Contacts with symptoms consistent

with TB regardless of reaction • Contacts <5 years of age• Immuno-suppressed/HIV contacts

Where, how, who makes the referral?

CXR requisition givenSputum collected as necessaryResults are sent directly to 496 HargraveContacts are referred to either Klinic,

Health Action Centre, Childrens Hospital or Respiratory Outpatients Clinic for assessment and treatment of LBTI

References

Curry International Tuberculosis CenterCanadian Tuberculosis Standards 6th

editionCanadian Immunization Guide 7th

editionManitoba Health Tuberculosis Protocol

December 2009