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• MDR TB : Multi drug Resistant TB– Rifampicin (RIF) and INH resistance

• XDR TB : Extensive Drug Resistant TB– INH and RIF (MDR-TB) and – Amikacin or Kanamycin or Capreomycin – and Ofloxacin, Moxifloxacin (Fluroquinolones)

• TDR TB : Totally Drug Resistant TB– Resistant to almost all known anti TB drugs

DST means Drug Sensitivity Test

Specificity is

True Negatives

d

Total No CAD

b + d

Sensitivity is

True positives

a

Total CAD

a + c

CAD by CAG

No CADby CAG

ECG +VETrue Positives

aFalse Positives

b

ECG – VEFalse Negative

cTrue Negatives

d

Total CADa + c

Total No CADb + d

TE

ST

GOLD STANDARD SnNOUT (Minimum FN)

SpPIN (Minimum FP)

Specificity is

True Negatives

180

Total No CAD

300

Sensitivity is

True positives

70

Total CAD

100

CAD by CAG

No CADby CAG

ECG + VETrue Positives

70False Positives

120

ECG – VEFalse Negative

30True Negatives

180

Total CAD100

Total No CAD300

TE

ST

GOLD STANDARDSnNOUT (Rules out

70%)

SpPIN (Confirms 60%)

Negative Predictive

Value

True Negatives

180

Total Negatives

210

Positive Predictive

Value

True positives

70

Total Positives

190

Test CAD by CAG

No CADby CAG

ECG + VETrue

Positives70

False Positives

120

Total +ves 190

ECG – VEFalse

Negative30

True Negatives

180

Total -ves 210

Total CAD100

Total CAD300

Grand Total 400

GOLD STANDARD PPV is 37%)

NPV is 86%)

• Sensitivity is the ability of the test to rule out disease confidently when the test result is negative.

• Specificity is the ability of the test to confirm disease confidently when the test result is positive.

• Positive Predict Value (PPV): useful in high prevalence situations

• Negative Predictive Value (NPV): useful in low prevalence situations

• Sensitivity and Specificity are unaffected by prevalence

HIV TBBOTH

3.5m 1.7m 2.5m

• 10 million new cases every year globally

• 3 million deaths annually worldwide

• Leading cause of death due to infectious disease

• 25% of all avoidable deaths are due to TB

• 95% of TB cases and 98% of deaths are in developing countries

• India contributes 2 million cases every year

• 0.5 million die of TB annually – 1 death / min

• 75% of cases are in productive age groups

• Increasing HIV infection increases TB burden.

• More than 10 m cases of TB yearly - world wide• India ranks 1st among the top 22 TB countries• 5 lakh cases of MDR TB per year (WHO)• Accurate and early diagnosis is most important

for effective case management and prevention of transmission of MTC

• We do not have an effective vaccine to prevent• Case finding and case holding are key issues• MDR, XDR and TDR cases are due to improper Rx.• Anonymous or atypical mycobacteria MOTT

• Tuberculosis is endemic in our country• Ours is high prevalence, high incidence scenario• Poverty, over crowding, lack of education, ½ Rx.• Large population and wide area – large burden• BCG vaccination is common – confounds skin test• MOTT – Anonymous mycobacteria are ubiquitous• Subclinical MTB infections are very common• New HIV burden throws a new serious challenge• MDR TB, XDR TB and now TDR TB – big challenge• Non compliance, self medication, quackery• We very well know about our Govt. programme

MDR TBMDR TB

Mutations in the MTB Genome

• Fever, cachexia, cough, sputum, chest pain, hemoptysis, fatigue, night sweats, raised ESR are notoriously present in many similar disorders

• Clinical signs of consolidation, cavitation, fluid, thickened pleura, neck glands can occur in a variety of conditions.

• Old treated TB is big confounder, DST is not done• Partially treated cases pose resistance problems• COPD, emphysema mimic and mask TB signs• Early lesions often are unsuspected until X-ray• The sensitivity and specificity are rather low.• Extra pulmonary poses even greater confusion

• Radiological features when clear cut are highly specific. Often early lesions may be missed.

• X-ray shadows can’t tell activity of disease• Old shadows are superimposed on fresh ones.• Effusions may be due to many causes• HRCT is expensive and again cannot speak of the

activity of disease.• Treatment decisions on imaging alone will be risky

as TB Rx is prolonged and potentially toxic• Over all - X-ray has high sensitivity, mod. Specificity• We can’t treat shadows. What about extra pulmonary ?

MTB and Its ProductsMTB and Its Products Humoral & Cellular ResponseHumoral & Cellular Response

• 120 years old technique, relatively simple

• Special techniques to improve the yield

• ZN method and Fluorescent microscopy

• Results will be reported with in hours

• Most cost effective method – RNTCP

• Requires good training & observer dependent

• Requires 5 x 103 bacilli per ml of sputum

• Proper collection of sputum is essential

• Three specimens are needed for Dx.

• Sensitivity is 30 to 60%, Specificity is high - 97%

• Corner stone of definitive diagnosis. Gold standard.• LJ medium or Middle Brook 7H10 & 11 Solid media• Kirchner’s or Middle Brook 7H9 broth – Liquid media• Slow growth – Mean time of 4 to 6 weeks (2-3 wks)• DST requires another 4 weeks; Contaminants problem• Combination of solid & liquid media is better• Micro colony detection, Sept Check AFB, MODS• Proper collection of sputum is essential.• High infrastructure cost, Not available readily.• Many factors decide the yield of positive culture• Highly specific 99.5% but moderately sensitive - 70%.

• Uses 14C labeled palmitic acid in the medium

• Based on metabolism of MTB – not on visible growth

• If the medium is metabolized - 14CO2 is released

• BACTEC system radiometric measurement gives GI

• Same BACTEC can be used for DST

• Significantly faster – 87% +ves in 7 d, 96% in 14 d

• DST can be completed in 8 days

• This proves cost effective in high prevalence areas

• Uses 14C labeled palmitic acid in the medium

• Based on metabolism of MTB – not on visible growth

• Mycobacteria Growth Indicator Tube (MIGT)

• Observed every 60 min for increase in fluorescence

• AFB metabolic utilization of O 2 in the fluorescent dye

• Intensification of fluorescence in the tube

• Rapid, accurate and cost effective method for high volume labs

• 960 tubes can be computer monitored simultaneously

• Can be used for DST also; Rapid in 4-6 days results

• MB / BacT System

– Non radiometric continuous monitoring system with computerized data base management. The system is based on colorimetric detection of CO2

• ESP Culture System

– Fully automated continuous monitoring of pressure changes with in the head space above the broth culture medium in a sealed bottle. Gas production or gas consumption by bacterial growth. Results in about 2 weeks

• Sequences of bacterial DNA will be amplified

• 10-1000 bacilli are sufficient for detection

• Rapid and results are available in a day

• Target IS6110, 65 kDa, 65 SrNA MTB Specific

• It is present up to 20 times in the MTB genome

• It can detected both in blood and in sputum

• Sensitivity 84%, Specificity 99%, PPV 94.2%

• NAAT – Nucleic Acid Amplification Test and

• TMA, SDA, NASBA, b-DNA, LiPA – other tests

• “Mycoreal” - A rapid real time PCR test for MTB

• Utilizes UTP/UDP system to avoid contamination

• Sensitivity 99%, Specificity 99.5%

• Detects all members of MTC group

• Can be used in pulmonary and extra pulmonary

• Sputum, Blood, Tissues - all can be tested

• No “ post PCR processing”. So no contamination

• Detects as low as 2 fg of MTB DNA

• Negative, positive and no template controls

• It is two-in-one: Detects presence of MTB by Real Time PCR + identifies if it is resistant to RIF

• Developed by Cepheid – Endorsed by WHO,

• TB Culture take 3 to 6 weeks, DST further 3 to 4 wks

• Rapid 100’, very simple, minimal training, field use

• Completely closed, No man errors, No contamination

• RIF resistance is a surrogate of MDR TB

• Sensitivity 91% detection in S-C+ / 100% in S+C+

• Specificity very high 99.2%, 98% for RIF resistance

• Govt. of India has started in 4 places, Available in labs

22nd October 2011

• This is a LiPA endorsed by WHO and FIND• Detects mutations in rpoB , Kat G and inhA• Rapid detection of RIF & INH Resistance – MDR• inhA inclusion detects even low levels of INH R• Sensitivity 93.6% RIF, 92.6% INH, 88.9% for MDR• Specificity is 100% for all types of patients• PPV is 100%, NPV is 90.3%• Smear +ve or culture +ve specimens • In smear –ve cases bacillary load will be low to

detect mutations for the drug resistance.

3 to 6 weeks

3 days3 days

4 to 9 weeks

4 days4 days

• This is also a LiPA – rapid test for XDR

• Detects mutations in gyrA, 16S rRNA, embB

• Sputum or Culture specimens of MDR TB only are tested for second line drug resistance

• India, China, SA and Russia, BD – together contribute for largest number of XDR TB.

• Culture and DST is not routinely done in our country. We miss a lot of MDR and XDR TB

• We realize only when the patient does not respond after 6 months of treatment.

• Routine DST is now essential in view of MDR, XDR TB burden. Also TDR TB will be most challenging

• DST based on solid media cultures take 3 to 4 weeks for 1st line and a further 3 to 4 weeks for 2nd line drug sensitivity

• RT PCR combined with Line Probe Assay (LiPA) will shorten this time most efficiently to 3 to 4 days

• If we use GeneXpert – MDR TB can be diagnosed in 100 minutes, even before the smear results come.

• The world is on the fast track but our TB Dx is on 120 years old ultra slow track. How do we win TB?

• MTB genome has regions of difference (RD)

• These RDs encode potential antigens for Dx.

• RD1 is responsible for secretion of ESAT6

• ESAT6 (6kDa) is specific antigen and a strong inducer of IFG by T cells of the TB patient.

• IFG is a cytokine secreted by sensitized T cells

• This ESAT6 is not recognized by BCG or NTM

• IFG levels increase with treatment – prognostic

• It is a measure of CMI in TB patients

• Sensitivity is 82 to 90%, Specificity is 96 to 99%

• These are IGRA – use three proteins specific for MTB – ESAT6 (early Secretory Antigen TB), CFP (Colony Forming Protein) and TB7.7 – All are proteins from different RDs

• This combination makes the test very specific as these are absent in BCG and NTM

• Rapid test – 1 day, available – moderately priced

• Does not distinguish between Latent Infection (LTBI) and active disease. It is an ELISA based test.

• Specificity 96 to 99%, Sensitivity 82 to 90%

• It is one of the latest tests – based on IGRA

• An FDA approved in vitro test based on ELISPOT

• Uses two separate panels of MTB complex – the ESAT6 and CFP10 – not present in BCG, NTM

• Detects both LTBI and Active TB (all forms)

• Useful in all ages, ethnicity, immunocompromised

• More sensitive compared to ELISA-TBFeron

• Sensitivity 95% and Specificity 97%

• Rapid test – in one day result is available

• Useful to test body fluids like plural, peritoneal, pericardial and cerebrospinal fluid.

• Commonly used for Dx. of TB pleural effusion

• Increased T lymphocytes and their increased activity increases ADA in the exudate

• In low prevalence areas – more false positives and low specificity. Combined with lymphocyte count it may be useful as a screening test.

• Not a replacement for culture or biopsy.

• Simple, cheap test to R/o TB in exudate effusions.

• Rarely useful as screening tests. Industry bias

• Low turn around time, Not available in all labs

• Very low sensitivity in smear negative cases and HIV positive cases

• Not useful in our country of high endemicity

• Ubiquitous nature of MOTT

• Sero conversion would have already occurred

• High cost, require trained staff, costly equipment

• Can’t separate MTB and NTM

• Strongly recommended by WHO – Not to be used

• Useful in non endemic countries with low TB rates

• Almost all adults in our population are manteaux positive because they are either BCG vaccinated or are exposed MTB or NTM in the air and soil.

• The protein (PPD) used in Manteaux test is non specific and is shared by BCG, MTB and NTM

• A positive Test in Indian adults has no meaning. In very young children high positivity may mean recent infection.

• Infection is not synonymous with disease.

• Sensitivity is also low. Specificity is nearing zero

False negatives

• In severe disease – Miliary TB

• In HIV infected

• In Sarcoidosis

• Technical factors

– Application, Reading,

– Improper storage of PPD

• Biological factors

– Poor nutrition, Infection

– Immunosuppressive drugs

– Malignancy, Age, Stress

False positives (Major Issue)

• Infection with NTM - non tuberculous mycobacteria

• BCG vaccination

• Booster effect or retest

• Natural infection with MTB in endemic counties and acquired CMI (herd immunity

• MPB 64 is a specific MTB antigen

• Patch test becomes positive after 3-4 days of application and lasts for a week

• Specificity of 100% and sensitivity of 98.1%

• Evaluated only in Philippines and needs to be reproduced in other settings.

• ESAT 6 (Early Secretory Antigen for TB) and CFP 10 (Colony Forming Protein) are specific proteins of MTB and are being tried in skin tests.

• We need to move fast from our ESR and Mx. test

• Clinical feature are good screening tool for tests

• Radiology has a good role but understand its limits

• Costly imaging like HRCT, MRI add nothing for Dx.

• Accurate Diagnosis, Complete Rx are the answers

• MDR, XDR and now TDR TB are great challenges

• DST has to be done routinely – at least on diagnosis

• RT PCR, Gene Xpert, IGRA, LiPA – a sea change

• Use ADA to exclude. Serology should not be used.

• Above all, remember our burden & poverty. Stop TB.

website: youtube: drsarmaji channel

Documents

total positives

total negatives

test cad

total ves

total ves

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cag ecg ve true positives