TB (Infection) or not TB? Who should we screen and treat?

Primary Care Conference

August 31, 2005

K. Mae Hla, M.D., M.H.S.

Learning Objectives

• Review guidelines for testing and treatment of LTBI using case examples

• Evaluate the rationale for targeted TST• Discuss factors influencing TST results and

interpretations• Assess the evidence of current treatment

recommendations for LTBI • Updates on new tests and treatment

recommendations

Case #1

43 year old female physician who underwent routine annual testing at UWHC: PPD was 10 mm. Previous year’s PPD was 0 mm. No known history of exposure but works with high risk patients

No history of BCGNo history of cough, low grade fever, night sweats or weight loss

What would you do with this patient?

Consider the test positive Consider the test negative Consider a Chest X-ray Disregard test results if chest x-ray is

negative since she’s older than 35 years

Case #2

• 32 year old man arrived from India 2 years ago

• TB tested during pre-employment exam• 23 mm induration • H/o BCG in childhood• No symptoms of active TB

What would you do with this patient?

Positive TST is due to BCG Old positive PPD No need to consider for INH treatment

since due to either of the above Disregard BCG and recommend INH

What would you do now?

Positive TB test is due to BCG Old positive PPD No need to consider for INH treatment

since due to either of the above Disregard BCG and recommend INH –

end of story Test further

Case # 3

• 28 y.o. woman with SLE, ESRD, S/P kidney transplant on immunosuppressive therapy

• PPD placed during hospitalization with acute lung infiltrate was 6 mm

• Is this PPD positive or negative?

Case # 4

36 y.o. diabetic male, PPD 13 mm, recently in prison, known exposure to INH resistant TB, no known prior PPDs, no acute symptoms, CXR-negative.

Is this person at risk of developing TB? What are his risk factors? What would you recommend he be treated

with?

Case # 5

• 30 y.o. male seen in clinic for naturalization physical

• Country of origin: England• Hx of BCG at age 13• PPD: 11 mm induration, never been

tested in past• CXR normal

Case # 5

Consider his PPD positive Consider his PPD negative Consider his pos PPD to be due to BCG

and not recommend INH Disregard BCG and consider 9 months

of INH

Case # 6

35 y.o. HIV positive male, PPD negative for past 2 yrs, tested 6 mm now; no known exposure history, no acute symptoms, CXR negative for active or old TB.

Is his PPD negative or positive?How likely is he to develop active TB?

General Principles in Screening

• The disease is common (prior probability)• The test is both accurate and reliable• Treating the disease at an early phase

will lead to improved outcome compared to that of treating it only when it manifests itself as active disease

• Treatment is feasible and not harmful

Reported TB CasesUnited States, 1953 - 1998

Year

10,000

20,000

*

*

30,000

50,000

70,000

100,000

Ca

ses

(Lo

g S

cale

)

*Change in case definition

53 60 70 80 90 98

Reported Cases of TB by Country of Birth - United States, 1986-1998

86 87 88 89 90 91 92 93 94 95 96 97 980

5

10

15

20

25

30

35

40

U.S.-born

All Cases

Foreign-born

Rec

ent

Cas

es p

er 1

00,0

00 p

opul

atio

n

Year

Areas of Concern

• TB cases continue to be reported in every state• Drug-resistant cases reported in almost every

state• Estimated 10-15 million persons in U.S.

infected with M. tuberculosis– Without intervention, about 10% will develop TB

disease at some point in life

Targeted TB Testing

• Identify persons with LTBI who would benefit by treatment of LTBI

• Find persons with TB disease who would benefit from treatment

• Groups that are not high risk for TB should not be tested routinely

• All testing activities should be accompanied by plan for follow-up care

Who should we screen?High Risk Groups for LTBI

Groups that should be tested for LTBI regardless of age:

• Persons at higher risk for exposure to or infection with TB

• Persons at higher risk for TB once infected

Persons at Higher Risk for Exposure to or Infection with TB

• Close contacts of person known or suspected to have TB

• Foreign-born persons from areas where TB is common

• Residents and employees of high-risk congregate settings

• Health care workers (HCWs) who serve high-risk clients

Persons at Higher Risk for Exposure to or Infection with TB (cont.)

• Medically underserved, low-income populations

• High-risk racial or ethnic minority populations

• Children exposed to adults in high-risk categories

• Persons who inject illicit drugs

World Region of Origin

TB Case Rates

Rates US Residence

<5 yr

Rates US Residence

>5 yr

United States 8.1 -- --

Established market economies

4.7 6.0 4.7

Former socialist economies of Europe

11.2 14.9 13.7

India 55.6 108.2 35.8

Latin America 33.7 68.4 30.8

Mainland China 40.6 89.7 30.7

Middle East 22.1 47.3 15.2

Other Asian countries 81.8 207.5 41.1

Sub-Saharan Africa 58.4 108.9 26.4

Total foreign-born 30.6 66.3 21.7

TB Case Rates* according to the length of Residence in the U.S. for Foreign-Born Persons, 1986-1993

* Rates are per 100,000 person-years, adjusted for age.

Persons at Higher Risk of Developing TB Disease once Infected

• HIV infected

• Recently infected (converted within 2 yr)

• Persons with certain medical conditions

• Persons who inject illicit drugs

• History of inadequately treated TB

Incidence of active TB in persons with a positive PPD by selected risk factors

Risk Factor TB Cases/1,000 person-years

Recent TB infection Infection <1 yr past 12.9 Infection 1-7 yr past 1.6Human immunodeficiency virus (HIV) infection 35.0-162 Injection drug use HIV seropositive 76.0 HIV seronegative or unknown 10.0

Relative risk* for developing active TB by selected clinical conditions

Clinical Condition Relative Risk

Silicosis 30 Diabetes mellitus 2.0-4.1 Chronic renal failure/hemodialysis 10.0-25.3

*Relative to control population; independent of TB test status

Relative risk* for developing active TB by selected clinical conditions

Clinical Condition Relative Risk

Gastrectomy 2-5 Jejunoileal bypass 27-63 Solid organ transplantation Renal 37 Cardiac 20-74 Carcinoma of head or neck 16

*Relative to control population; independent of TB test status

Are HCWs at high risk of LTBI?

• Prevalence of TB in the community, facility, institution

• Contact with high risk patients (HIV positive pts., injection drug users, homeless pts.)

• Increased risk in certain occupational groups (respiratory therapists)

• Individual risk factors (diverse workforce)

Test accuracy and reliability

• Prior probability of disease

• Method of administration

• Timing of reading

• Interpretation

Administering the Tuberculin Skin Test

•Inject intradermally 0.1 ml of 5TU PPD tuberculin

•Produce wheal 6 mm to 10 mm in diameter

•Do not recap, bend, or breakneedles, or remove needles from syringes

•Follow universal precautions for infection control

Reading the Tuberculin Skin Test

• Read reaction 48-72 hours after injection

• Measure only induration

• Record reaction in millimeters

Classifying the Tuberculin Reaction

>5 mm is classified as positive in• HIV-positive persons

• Recent contacts of TB case

• Persons with fibrotic changes on chest radiograph consistent with old healed TB

• Patients with organ transplants and other immunosuppressed patients

>10 mm is classified as positive in

• Recent arrivals from high-prevalence countries

• Injection drug users

• Residents and employees of high-risk congregate settings (hospitals, prison, NH)

• Mycobacteriology laboratory personnel

• Persons with clinical conditions that place them at high risk

• Children <4 years of age, or children and adolescents exposed to high-risk adults

Classifying the Tuberculin Reaction (cont.)

>15 mm is classified as positive in

• Persons with no known risk factors for TB

• HCWs otherwise at low risk for TB disease and who received baseline testing at start of employment

Factors that May Affect the Skin Test Reaction

Type of Reaction Possible Cause

False-positive Nontuberculous mycobacteria

BCG vaccination

False-negative Anergy

Recent TB infection

Very young age (<6 months old)

Live-virus vaccination

Overwhelming TB disease

Errors in application & interpretation

Boosting

• Some people with LTBI may have negative skin test reaction when tested years after infection

• Initial skin test may stimulate (boost) ability to react to tuberculin

• Positive reactions to subsequent tests may be misinterpreted as a new infection

Two-Step Testing

• If first test positive, consider the person infected

• If first test negative, give second test 1-3 weeks later

• If second test positive, consider person infected

• If second test negative, consider person uninfected

Use two-step testing for initial skin testing of adults who will be retested periodically

BCG Vaccination and TST

• Tuberculin skin testing is not contraindicated in BCG-vaccinated persons

• Treatment for LTBI should be considered for any BCG- vaccinated person whose skin test reaction is >10 mm, if any of these circumstances are present:- Was contact of person with infectious TB- Was born or has resided in a country with high

TB prevalence - Is continually exposed to populations where TB

prevalence is high

BCG Effect vs. LTBI

• Case # 2 – Likely LTBI given country of origin and

recent arrival

• Case # 5– Likely BCG effect

New Test for Detecting LTBI• QuantiFERON (QFT)– FDA approved in 2001

– in vitro cytokine assay – quantification of interferon-gamma released

from sensitized lymphocytes in whole blood incubated overnight with PPD from M.TB

– will not detect M. Bovis strains used in BCG – QFT results: % Tuberculin response: cut point

of 15% for people with identified risk, 30% for people with no identified risk for infection

QuantiFERON-TB Test

• Advantages– Less subjective than interpretation of the TST– Requires single patient visit– Helps in detecting LTBI in patients who have

had BCG– Does not boost anamnestic immune responses– Maybe more efficient and cost effective than

TSTs in screening HCWs for infection with M.TB

QuantiFERON-TB Test (QFT)

• Disadvantages– limited laboratory and clinical experience– process within 12 hours after blood collection– ability of QFT in predicting progression to TB

disease not evaluated– confirmation of a positive QFT with TST

recommended especially if probability of LTBI low

– active TB still needs to be ruled out

Who Should We Treat?

• Persons who are at very high risk of developing TB once infected should be given treatment regardless of age

Patients who should be treated if their TST result is >5, regardless of age

• HIV-positive persons

• Recent contacts of TB case

• Persons with fibrotic changes on chest radiograph consistent with old healed TB

• Patients with organ transplants and other immunosuppressed patients

Consider treatment if TST >10 mm

• Recent immigrants from high-prevalence countries

• Injection drug users

• Residents and employees of high-risk congregate settings

• Mycobacteriology laboratory personnel

• Persons with clinical conditions that place them at high risk

• Persons living in areas with high incidence of TB

• Children <5 years of age, or children and adolescents exposed to high-risk adults

Efficacy of INH in treating LTBI

• Many RCTs of isoniazid in 1950-1960• Industrialized and developing countries• involving >100,000 participants at risk for

TB– Children with primary TB, contacts of TB

cases, positive PPDs, institutionalized pts,and persons with inactive TB

Efficacy of Treatment with 12 months of INH

• Decrease in TB among all participants varied from 25 to 92%

• In analysis restricted to compliant persons, protective efficacy was approximately 90%

Efficacy of various durations of isoniazid preventive therapy for persons with fibrotic

lesions, by length of treatment (IUAT Trial, 1969-77)

5 yr TB incidence* (% reduction)

Group Placebo 12 wk 24 wk 52 wk

All participants (n = 27,830) 14.3 11.3 (21) 5.0 (65) 3.6 (75)Adherent participants (n = 21,635) 15 9.4 (31) 4.7 (69) 1.1 (93)Fibrotic lesions <2cm2

(n = 18,663) 11.6 9.2 (20) 4.0 (66) 4.2 (64)Fibrotic lesions >2cm2

(n = 8,428) 21.3 16.2 (24) 7.0 (67) 2.4 (89)

Rating (A-E)

A. Preferred; should generally be offeredB. Alternative; acceptable to offerC. Offer when preferred or alternative regimens cannot be givenD. Should generally not be offeredE. Should never be offered

Strength of Treatment Recommendations

Evidence (I-III)

I. At least one randomized trial with clinical endpoints

II. Clinical trials that either are not randomized or were conducted in other populations

III. Expert opinion

Quality of Evidence Supporting Recommendation

Rating and EvidenceDuration

Drugs (mo) Interval HIV- HIV+

Isoniazid 9 Daily A (II) A (II)Twice weekly B (II) B (II)

Isoniazid 6 Daily B (I) C (I)Twice weekly B (II) C (I)

Rifampin 4 Daily B (II) B (III)

Rifampin-pyrazinamide Generally should not be offered for treating

LTBI in both HIV positive and negative (D/II)** As revised in the ATS/CDC update, MMWR 2003 & JAMA 2005

Treatment of LTBI with Isoniazid (INH)

• 9-month regimen considered optimal

• Children, HIV infected persons and those with CXR evidence of prior TB (fibrotic lesions) should receive 9 months of therapy

• Can be given twice-weekly only if directly observed

• 6-month regimen is an acceptable alternative

Treatment of LTBI with Rifampin

• 4-month regimen considered acceptable as alternative

• Can be given twice-weekly only if directly observed

• Persons with HIV infection, and with CD4 cell counts <100 should not be treated with intermittent regimens, and should receive DOT, if feasible

Treatment of LTBI with Rifampin and Pyrazinamide (RZ)

• Reports of severe liver injury and death• CDC & ATS have revised previous

recommendations• RZ should generally not be offered for treatment

of LTBI for both HIV positive and negative• Use only after consultation with infectious disease,

if potential benefits outweigh risk and patient has no contraindications

Contacts of INH-Resistant TB

• Treatment with Rifampin, 4 month continuous regimen

• HIV infected: should not administer protease inhibitors or delavirdine concurrently with rifampin. Rifabutin could be used instead with appropriate dose adjustments

MDR TB Cases, 1993 - 1998

None

> 1 case

Contacts of Multidrug-Resistant TB

• Use 2 drugs to which the infecting organism has demonstrated susceptibility

• Treat for 6 months or observe without treatment

(HIV-negative)

• Treat HIV-positive persons for 12 months

• Follow for 2 years regardless of treatment

Pregnancy and Breast-feeding

• INH daily or twice weekly

• Pyridoxine supplementation

• Breast-feeding not contraindicated

Adverse Effects

• INH – rash, elevated LFTs, hepatitis, peripheral

neuropathy, mild CNS effects, drug interactions

• Rifampin– rash, hepatitis, fever, thrombocytopenia, drug

interactions with PIs or NNRTIs

• Pyrazinamide– GI upset, hepatitis, rash, arthralgias, gout (rare)

Monitoring PatientsBefore treatment for LTBI is started, clinicians

should

• R/O possibility of TB disease with CXR• Determine history of Rx for LTBI or disease• Determine contraindications to treatment:

medications and medical history• Recommend HIV testing if risk factors are

present• Use State and Local Health Departments

Monitoring Patients (cont.)

• Baseline laboratory testing not routinely indicated

• Baseline hepatic measurements indicated for• Patients whose initial evaluation suggests a liver

disorder or regular use of alcohol• Patients with HIV infection• Pregnant women and those in immediate

postpartum period• Patients with history of chronic liver disorder

Monitoring Patients (cont.)

At least monthly (public health nurse), evaluate for

• Adherence to prescribed regimen is major determinant of outcome of treatment

• Signs and symptoms of active TB disease

• Signs and symptoms of hepatitis

• Prompt evaluation of side effects and changes in treatment crucial

Guidelines!!!

Sigourney Weaver: “I am Zule. Do you want this body?”Bill Murray: “Is this a trick question?”Sigourney Weaver: “Take me now!”Bill Murray: “I make it a rule never to get

involved with possessed people”

[Sigourney Weaver kisses Bill Murray fiercely]

Bill Murray: “Actually, it’s more of a guideline than a rule”

References• Am J Respir Crit Care Med 2000;161:S221-247• Targeted Tuberculin Testing and Treatment of Latent TB

Infection. MMWR Weekly Report. DHHS. CDC. 2000;49:1-51• Guidelines for Using the QuantiFERON TB test for

diagnosing Latent TB infection. MMWR 2003;52;15-18• Update: Adverse Event Data and Revised ATS/CDC

Recommendations against use of Rifampin and Pyrazinamide for Treatment of Latent TB Infection-United States, 2003 MMWR 2003:52(31) 735-739

• Update on the Treatment of Tuberculosis and Latent Tuberculosis infection. Blumberg H. et al JAMA 2005;293 (22) 2776-2784