Diagnosis of Tuberculosis Diagnosis of Tuberculosis 20102010

New Tools, Tricks, Thinking?New Tools, Tricks, Thinking?

John Bernardo, M.D.John Bernardo, M.D.Pulmonary Section, Pulmonary Section,

Boston University School of MedicineBoston University School of MedicineMassachusetts Department of Public HealthMassachusetts Department of Public Health

ObjectivesObjectives

• Primary Priority: Diagnosis of Tuberculosis, 2010

• Target the Reservoir: Identify Latent TB Infection

HistoryHistory

• 26 y/o F physician from S. Asia– Pos TST (22mm) on pre-employment evaluation– Exam and CXR: neg– Offered treatment for LTBI, but declined

• “It’s my BCG – in my country everyone has a positive test”

• 8 months later presents with fatigue/malaise, cough x 4+ wk, fever– MD prescribed antibiotic (Levaquin®)

• Symptoms improved – did not clear -- then returned

• 2 MD visits later (and 2 more courses abx later):

Saskatchewan Lung Association

OOPSOOPS

Sputum 4+ smear positive

MTD+: MTb Complex

Diagnosis of TB, 2010Diagnosis of TB, 2010Some things change; Some donSome things change; Some don’’tt

• Diagnosis follows “Suspicion”• When should we “Think TB”?

– Who is at risk for TB?– Is TB presenting differently than in the past?– How do we make the diagnosis? – And … are there new ways to improve

diagnostic capacity?

Diagnosis: Define Groups atDiagnosis: Define Groups at--RiskRiskEpidemiology of recent cases

• In US– Majority of cases is non-US born; from high prevalence countries– Community-specific (e.g., homeless, substance abusers, Haitians, …)– Children from high-prevalence groups

• Medical risk factors (if infected)– HIV 7-10%/yr– Diabetes ? 4%/yr – ESRD 10-20%/yr– Immunosuppressive therapies – including Organ transplant recipients,

anti-TNF-α agents, chronic steroids– Age

• Recent transmission versus reactivation

Elderly US-born still appear (born when TB still widely endemic) Still a problem; usually represent reactivation disease

Diagnosis of TBDiagnosis of TB

• History (personal)• Symptoms

– Specific to system involved• e.g., cough (pulmonary), chest pain (pericardial), …

– Nonspecific (constitutional)• e.g., fever, wt loss, night sweats, fatigue, …

– May be absent - up to 25%• Chest radiograph

Epidemiology and Presentationin Context

• Older gentleman from homeless shelter– Change in chronic cough, hemoptysis, possible wt loss– CXR - RUL cavitary infiltrate

• 1 y/o US born child, Nigerian family– Failure to thrive; “a cold”– CXR - LUL infiltrate; hilar adenopathy

60 y/o Hobo, seen at Pine StInn w 3wk cough, sputum

Riding the RailsRiding the Rails• Chronic cough, EtOH abuse

– Just back from MN (hobo convention)• Feels lousy

– Appetite poor• Admitted – started HRZE

– TST – 7mm– Sputum AFB smear-positive– MTD negative (no inhibitors identified)

• Better – Case?• Culture positive: M. avium complex

12 mos old M w cough,failure to thrive

Kid’s TB• Presentation, epidemiology

– US-born; no travel or known contact to TB case– 1 y/o; small for age, irritable – TST 20mm

• Clinical suspicion: CXR• Child admitted, started HRZ(E)

– Cultures never grew (gastric aspirates x3)– Improved on therapy: Clinical Case

• Grandma– CXR: “old disease”– Induced sputum smear negative; MTD-positive

• Subsequently culture-positive MTb

Grandma – coughing (denied),visiting; read as “old granulomatous disease”

Chest RadiographStill a Good Screening Tool*

• Time: minutes to hours• Sensitivity: excellent (but there are exceptions)

– Single view adequate in most settings (children <11 - 2 views)

• Specificity: poor– Up to 1/3 of pulmonary TB – non-classic radiograph

• Advantage: inexpensive screening of potentially active pulmonary cases

• Disadvantages: cost? – Requires skilled interpretation

* BUT only in appropriate setting

Diagnosis of TuberculosisDiagnosis of Tuberculosis

Suspicion !

Suspicion !!

Suspicion !!!Suspicion !!!

Diagnosis of Tuberculosis:Diagnosis of Tuberculosis:Risks, Massachusetts, 2009Risks, Massachusetts, 2009--1010

• Homeless• Non-US Born – from TB-endemic countries• Immunosuppressed• Hx of past TB• TST+ contact of case• TST+ child (< 4 yr)

Barry Chin, Boston Globe, 10/15/2008

TB is LocalCreate New Tools:Create New Tools:

Cough LogCough Log

• Pine Street Inn Shelter– Counselors in dorms observe guests

at night• Coughing for 3 days in a row

– Triggers physical evaluation, CXR

PSI TB ClinicPSI TB Clinic

Diagnosis of TB:Diagnosis of TB:Demonstration of Demonstration of M. tuberculosisM. tuberculosis

• The Gold Standard• Ability to isolate organism varies with

– Location of disease– Density of organisms at disease site

• May be reduced in advanced HIV

Location of Disease?Location of Disease?

• Pulmonary TB– In past, approx. 85% of cases– Recent trend downward (~80%)

• Increase in non-US-born cases, HIV

• Extra-pulmonary – Approx. 20% of cases, can involve any (or multiple)

organ(s)• Lymphatic, renal/GU, bone-joint, CNS, …

TB is a Clinical Diagnosis TB is a Clinical Diagnosis (most of the time)(most of the time)

• TB is a clinical diagnosis– Most clinicians will initiate multi-drug therapy

if the disease is suspected on clinical grounds– But many cases go undiagnosed until a

laboratory reports a positive culture• How is that diagnosis confirmed?

– In the laboratory

Diagnosis of Tuberculosis Diagnosis of Tuberculosis –– 11

• Secretions or tissue - subjected to laboratory techniques to identify organism– Smear, pathology, culture, molecular

• Can be done as outpatient or inpatient

• For outpatients, consider possible risk to others

• For inpatients, use respiratory isolation if risk of transmission to others

Diagnosis of Tuberculosis Diagnosis of Tuberculosis –– 22

• Pulmonary TB– Spontaneous sputum: 3 good samples (1 q8h)– Induced sputum: nebulized 3% saline– Bronchoscopy– Gastric aspirates – Lung biopsy

• Pleural TB– Pleural fluid (exudate, low glucose, increased ADA) – 20%– Pleural biopsy with culture – 90%

• Other secretions, tissue, blood – May be subjected to standard laboratory testing

SOLUS ScannerSnap-on Tools

DiagnosticsDiagnostics

Smears: Identification of Stained AFB

•• Time: minutesTime: minutes•• Sensitivity: variesSensitivity: varies

–– 3030--90% for sputum90% for sputum–– Least sensitive detection method: detects 10Least sensitive detection method: detects 1044

AFB/ml (improved w fluorescent stain to 10AFB/ml (improved w fluorescent stain to 1033/ml)/ml)•• Specificity: poorSpecificity: poor•• Advantages: Advantages:

–– Detection of potentially Detection of potentially infectiousinfectiouscasescases

–– May be used to monitor treatmentMay be used to monitor treatment

Red Snappers

AFB

Pathology: The Granuloma, +/- AFB

Solid Media: Routine CultureSolid Media: Routine Culture

•• Time: 3Time: 3--8 weeks8 weeks•• Sensitivity: variesSensitivity: varies

–– Better than smear: 10 Better than smear: 10 –– 100 AFB/ml can be detected100 AFB/ml can be detected–– 80 80 –– 90% of US cases are culture positive90% of US cases are culture positive

•• Specificity: excellent Specificity: excellent (the Gold Standard)(the Gold Standard)

•• Advantage:Advantage:–– Rapid identification Rapid identification once growing once growing (gene probes) (gene probes) –– Confirms diagnosis (if positive)Confirms diagnosis (if positive)–– Can use for drug susceptibilities (adds weeks)Can use for drug susceptibilities (adds weeks)–– Can use to monitor treatmentCan use to monitor treatment

Liquid Media: Rapid CultureLiquid Media: Rapid Culture

•• Time: 7Time: 7--21 days21 days•• Sensitivity: variesSensitivity: varies•• Specificity: very good to excellentSpecificity: very good to excellent•• Advantage:Advantage:

–– More rapid identification of organism (gene probes)More rapid identification of organism (gene probes)–– Confirms diagnosis (if positive)Confirms diagnosis (if positive)–– Can use for rapid drug susceptibilities (simultaneous)Can use for rapid drug susceptibilities (simultaneous)

Impact ?Impact ?Nucleic Acid AmplificationNucleic Acid Amplification

•• Two tests approved by FDA: MTD and Two tests approved by FDA: MTD and AmplicorAmplicor–– MTDMTD approved for smearapproved for smear--pos or pos or negneg sputum/respiratory secretionssputum/respiratory secretions

•• vsvs culture: sensitivity 80%; specificity 95%culture: sensitivity 80%; specificity 95%–– PPV ~ 80%; NPV ~ 86%PPV ~ 80%; NPV ~ 86%

•• False positive: contaminants; patient on treatmentFalse positive: contaminants; patient on treatment•• False negative: inhibitors of the reaction; low volumeFalse negative: inhibitors of the reaction; low volume

•• Predictive value is influenced by MD index of suspicion and Predictive value is influenced by MD index of suspicion and population testedpopulation tested

•• Still need cultureStill need culture–– Identification & drug susceptibility testing (DST)Identification & drug susceptibility testing (DST)

•• Recommended for initial sputum in new, Recommended for initial sputum in new, realreal suspectssuspects–– Should become Standard of CareShould become Standard of Care

•• OffOff--label applications (e.g., CSF, tissue)label applications (e.g., CSF, tissue)…… Careful Careful ……CDC: MMWR, 1/16/09

Application & Interpretation

Sputum, Respiratory Secretions

NAA Positive NAA Negative

Dx of TB established; cult. still required

Consider clinical picture and repeat testing

Consider clinical picture and repeat testing

Unlikely that M.tbwill be grown from sample (if controlled for inhibitor)

CDC: MMWR, 1/16/09

Rapid Molecular Detection of Drug ResistanceMolecular Beacon (rt-PCR-based) Assays*

Rapid Molecular Detection of Drug ResistanceRapid Molecular Detection of Drug ResistanceMolecular Beacon (Molecular Beacon (rtrt--PCRPCR--based) Assays*based) Assays*

if no mutation is detected in target region →fluorescence

if target contains mutation, beacon will not anneal → no fluorescenceE. Desmond,

CA State Laboratory

* not FDA-approved

Genes Associated with INH and RMP Resistance

• Rif resistance– rpoB core region (>95%)

• INH resistance– katG, inhA, ahpC, ndh (~85%)

E. Desmond, CA State Laboratory

Rapid Molecular Testing for Rifis available from CDC-TB Lab

Identification of Identification of M.tbM.tb by Differential DNA Fluorescence Stainingby Differential DNA Fluorescence StainingUsing Flow CytometryUsing Flow Cytometry

Courtesy: N. Pearlmutter, H. Shapiro

Courtesy: N. Pearlmutter, H. Shapiro

A Minimalist Imaging CytometerA Minimalist Imaging Cytometer

Latent TB Infection

Primary TB in a Child

- Delayed-type Hypersensitivity develops 8-10wk post-infection: TST or IGRA-positive

Latency of M. tuberculosis

• Environment of granuloma favors altered metabolism:• Low pO2• Reduced CHO• High Fat

• Replication time >>> 20hr.• Loss of acid fast staining properties• Mechanism(s) unknown

• Genetic switch?

• Lifetime risk of Reactivation

- Tubercle bacilli - “dormant”- Usually positive TST/IGRA- No symptoms- Normal Examination- Normal chest radiograph- NOT infectious- Sputum smears and cultures are negative

- Not a “case” of TB

Latent TB InfectionATS/CDC LTBI Recommendations:*

Diagnostic Testing and Treatment

Target testing to TB high risk- Contacts, medical conditions, homeless, prisoners- Recent immigrants, TST-neg w recent travel, underserved

Do NOT test- Low-risk persons- Known TST-pos- Recent (6wk) live virus vaccination (TST)

Populations for LTBI therapy- High TB-risk (including over 35), including recent immigrants- High TB-risk pregnant women

TST+ (IGRA+) and risk stratification ≡ “infected”Process:

- Hx, PE, and CXR for infected individuals- If NO evidence of disease: LTBI

** AJRCCM, April, 2000AJRCCM, April, 2000

Frequency of Screening

Whom should be retested, and how often?– Depends on ongoing risk of TB exposure

– Re-test your patients who have extended travel to high risk areas or other possible exposures (e.g., healthcare workers with potential TB exposure)

The New Immigration Process A Giant Step

• IMMIGRANTS, REFUGEES, and TBScreened in country of origin: – Evaluated for active TBactive TB

•• CXR, sputum smear/cultureCXR, sputum smear/culture•• Complete treatment prior to leavingComplete treatment prior to leaving

– Children (<15 y/o) undergo skin testing • In the US

– Those applying for an adjustment of status are evaluated for LTBI but treatment is not mandatedtreatment is not mandated

• Not evaluated:– Visitors, students, temporary workers, undocumented

CDC

Administering the TST

Create wheal6-10mm diam.

Reading the Skin TestReading the Skin Test

• Read @ 48-72 hours• Must be measured by

a professional TRAINEDTRAINED to read TB Skin Tests

• Size of the “bump” is measured, recorded in mm

10mm10mm

5mm5mm

15mm15mm

Interpretation of TSTDepends on patient risk

Size of TST

Who should be considered positive?

> 5 mm 1. Immunosuppressed person, especially HIV+2. Close contact of infectious TB case 3. Lesion on CXR consistent with old TB

> 10 mm 1. From a high incidence group (e.g., from area where TB is endemic such as certain countries, prisons, nursing homes, homeless shelters; intravenous drug users; medical risks)

2. Recent TST converter (defined: 2 yr; >10mm increase)> 15 mm 1. No known risk factors for TB

BCG - Bacille Calmette Guerin

• Derived from a strain of M. bovis• Not accepted/recognized in U.S. as

protection against TB• Not standardized vaccine• Efficacy studies range from 0-80% • Can confound tuberculin skin test

– But consider patient to be TB infected if TST positive

InterferonInterferon--Gamma Release Gamma Release Assays (IGRA)Assays (IGRA)

• In vitro assays for cell-mediated immunity to M. tuberculosisantigens– Utilize whole blood– Measure release of IFN-γ by circulating T lymphocytes following

stimulation with TB antigens (specific)• QuantiFERON®-TB approved by FDA in 2001 as “… an aid to

the diagnosis of TB infection.”• QFT-Gold test US FDA approved in 2005• QFT-Gold in-Tube test approved 2007• T Spot®-TB test approved 2008• Revised Guidelines, June, 2010

– CDC: http://www.cdc.gov/mmwr/PDF/rr/rr5905.pdf (MMWR, 6/25/10)– CTC (Canada): http://www.phac-aspc.gc.ca/publicat/ccdr-rmtc/10pdf/36-acs-5.pdf

Species specificity of ESAT-6 & CFP-10Environmental strains

AntigensESAT CFP

M abcessus - -M avium - -M branderi - -M celatum - -M chelonae - -M fortuitum - -M gordonii - -M intracellulare - -M kansasii + +M malmoense - -M marinum + +M oenavense - -M scrofulaceum - -M smegmatis - -M szulgai + +M terrae - -M vaccae - -M xenopi - -

Tuberculosis complex

Antigens

ESAT CFP

M tuberculosis + +M africanum + +M bovis + +BCG substrain

gothenburg - -moreau - -tice - -tokyo - -danish - -glaxo - -montreal - -pasteur - -

Japan Study QFT-G

AJRCCM. 2004; 170:59.

ESAT-6 or CFP-10* ESAT-6 or CFP-10*

0.0

0.5

1.0

1.5

2.0

10

20

30

2

Culture confirmed TB(prior to treatment)

Low Risk for TB(BCG vaccinated)

n = 118105 (89.0%) positive

n = 217213 (98.2%) negative

IFN

-gam

ma

(IU/m

L)

Interpreting IGRA ResultsInterpreting IGRA Results

• Negative: Same interpretation as negative TST• Positive: Same interpretation as positive TST

– Medical evaluation and chest x-ray are still needed to exclude TB disease and confirm LTBI

• Indeterminate: Test failure– Repeat test

• Borderline: (T-Spot® only) – Repeat test

CDC: MMWR, 6/25/10

Advantages of IGRAs

• Single patient visit• IGRA draw does not “boost” subsequent IGRA tests

– But TST may boost subsequent IGRA

• Less likely positive in BCG-vaccinated: Specificity• “Objective” read-out• Results available in 1-2days• Cost benefits (??)• Culture- and ethnic-naïve

Limitations of IGRAs• Limited data in many groups, such as those with

impaired immune function and children (<5 y/o)• High indeterminate results, poor reproducibility

shown in some studies• No good definition of conversion

– Currently: negative → positive ≡ conversion

• The ability of IGRAs to predict risk of progression to TB disease has not been determined – May be different than in those with a positive TST

• As with TST, IGRAs may be useful as a diagnostic aid within certain clinical contexts – Use judgment when interpreting these tests

Rete An Sante“Stay Healthy”