tuberculin testing

DR.T.V.RAO MD 1

Dr.T.V.Rao MD

TUBERCULIN SKIN TESTING

MANTOUX TUBERCULIN SKIN TEST

TUBERCULOSIS: PRIMARY INFECTION

• 95% of cases begin with pulmonary focus

• usually a SINGLE focus• hypersensitivity

develops 2 to 6 weeks• until then, focus may

grow larger• hypersensitivity brings

caseation

PRIMARY INFECTION: LYMPHO-HEMATOGENOUS SPREAD

• 8-14 weeks after onset of TB• usually occult• Mantoux positive during this

phase• body wide seeding occurs during

this phase• bone, kidney, meninges etc.• 3% of children with nl CXR’s

develop calcifications in lung apices (SIMON FOCI)

DR.T.V.RAO MD 4

USUAL PROGRESSION OF PRIMARY INFECTION

infection

Lympho-hematogenous spread

healed PRIMARY infection

DR.T.V.RAO MD 5

PROGRESSIVE PRIMARY DISEASE

pleural effusion

cavitation

lymph node involvement

DR.T.V.RAO MD 6

TUBERCULIN SKIN TESTING

• The Mantoux tuberculin skin test (TST) is the standard method of determining whether a person is infected with Mycobacterium tuberculosis. Reliable administration and reading of the TST requires standardization of procedures, training, supervision, and practice.

The issues:

• Applying the tuberculin skin test

• Reading the test

• Interpreting the test – including in children

• Management of positive TST

DIAGNOSIS OF LATENT TB WITH THE TUBERCULIN SKIN TEST

DR.T.V.RAO MD 7

DR.T.V.RAO MD 8

INDICATIONS FOR SKIN TEST SCREENING• Persons with signs and/or symptoms suggestive of tuberculosis disease

• Recent contacts of persons known or suspected to have tuberculosis

• Persons with undiagnosed upper lobe fibrotic lesions

• Persons infected with HIV

• Alcoholics and intravenous drug abusers

• Persons with medical conditions known to increase the risk of disesase if infection has occurred:

• silicosis, gastrectomy, jejunoileal bypasss, significant weight loss below IBW, chronic renal failure, diabetes mellitus, high dose corticosteroid treatment or other immunosuppressive therapy, leukemia, lymphoma, malignancy

• Groups at high risk of infection:

• Latin America, Oceana, medically underserved populations, residents of long term care facilities

• Groups that would pose a significant risk to others if diseased: employees of health care facilities, schools, child care facilities

ATS/CDC

DR.T.V.RAO MD 9

THE TB SKIN TEST: MATERIALS• OLD TUBERCULIN

• culture of TB bacillus in glycol peptone broth

• TB “tine” test

• PURIFIED PROTEIN DERIVATIVE (PPD)• TB bacillus grown in Long’s media, filtered after heating

• adopted by WHO as standard in 1950

• PPD-S 1952

• dose = 5 IU

DR.T.V.RAO MD 10

• Intra-dermal

• quality control important

• trained practioner necessary

• Delayed hypersensitivity

• cell mediated

• 48-72 hours• False negative

• immuno-compromized conditions

• measles/measles immunizations

• Nonspecific reactions

• increase >10 IU

• cross reactions, atypical MB

THE TB (MANTOUX) SKIN TEST

DR.T.V.RAO MD 11

APPLYING THE TUBERCULIN SKIN TEST

Courtesy of Dr. Marc Steben

DR.T.V.RAO MD 12

APPLYING THE TUBERCULIN SKIN TEST

DR.T.V.RAO MD 13

REACTION TO THE TUBERCULIN SKIN TEST

Courtesy of Dr. Marc Steben

DR.T.V.RAO MD 14

READING THE TUBERCULIN SKIN TEST

Courtesy of Dr. Marc Steben

• Read 2-3 days after placing the test

• Feel for induration

• Color change without induration is not included in the measurement

• Use a ruler or calipers

• Have someone else check if unsure

• Always document the exact size (mm) – not just “positive” or “negative”

READING THE TUBERCULIN SKIN TEST

DR.T.V.RAO MD 15

DR.T.V.RAO MD 16

• A positive TB skin test only tells that a person has been infected with TB bacteria. It does not tell whether the person has latent TB infection (LTBI) or has progressed to TB disease.

A POSITIVE SKIN TEST ONLY INDICATES

DR.T.V.RAO MD 17

• The reaction should be measured in millimetres of the induration (palpable, raised, hardened area or swelling). The reader should not measure erythema (redness). The diameter of the indurated area should be measured across the forearm (perpendicular to the long axis).

READING THE SKIN TESTING IN TUBERCULOSIS

PRIMARY INFECTION: LYMPHO-HEMATOGENOUS SPREAD

• 8-14 weeks after onset of TB• usually occult• Mantoux positive during this

phase

• body wide seeding occurs during this phase• bone, kidney, meninges etc.• 3% of children with nl CXR’s

develop calcifications in lung apices (SIMON FOCI)

• Read 2-3 days after placing the test

• Feel for induration

• Color change without induration is not included in the measurement

• Use a ruler or calipers

• Have someone else check if unsure

• Always document the exact size (mm) – not just “positive” or “negative”

READING THE TUBERCULIN SKIN TEST

DR.T.V.RAO MD 19

DR.T.V.RAO MD 20

FACTORS CAUSING DECREASED ABILITY TO RESPOND TO TUBERCULIN

• Factors related to the person being tested• Infections

• Viral (measles, mumps, chickenpox)

• Bacterial (typhoid fever, brucelosis, typhus, pertussis, overwhelming TB,

• Fungal (South American blastomycosis)

• Live virus vaccinations (MMR)

• Metabolic derangements (chronic renal failure)

• Nutritional factors (severe protein depletion)

• Diseases affecting lymphid organs (Hodgkin’s lymphoma, chronic lymphocytic leukemia, sarcoidosis)

DR.T.V.RAO MD 21

FACTORS CAUSING DECREASED ABILITY TO RESPOND TO TUBERCULIN (CONTD)

• Drugs (corticosteroids, other immunosuppressive agents)

• Age (newborn, elderly)

• Recent overwhelming infection with M. tuberculosis

• Stress (surgery, burns, mental illness, graft versus host reactions)

• Factors related to the tuberculin used

• Factors related to the method of administration

• Factors related to reading the test and recording results

DR.T.V.RAO MD 22

MILIARY DISEASEGENERALIZED HEMATOGENOUS TUBERCULOSIS

• generalized dissemination through bloodstream

• caseous focus ruptures into blood vessel

• growth of tubercle within the blood vessel

• may be acute, occult or chronic

• uniformly fatal if not treated

• rare

• usually occurs in the first 4 months after primary infection

MILIARY Disease• millet seed appearance

on X-ray

• Mantoux positive?• Most children still have

active primary complex when miliary disease strikes

• most develop meningitis

DR.T.V.RAO MD 24

Evaluate for active TB• Re-check

symptoms and exam – cough, fever, weight loss, enlarged lymph nodes, dyspnea

• Chest X-ray, if possible

EVALUATION OF A PATIENT WITH POSITIVE TST

DR.T.V.RAO MD 25

• Programme Created by Dr.T.V.Rao MD for Medical and Health Care Workers in

the Developing World • Email

• doctortvrao@gmail.com