case finding and diagnosis

Case Finding and Diagnosis

Module 5 – March 2010

Project Partners

Funded by the Health Resources and Services Administration (HRSA)

Case Finding Steps in Diagnosing TB• Medical History

• Bacteriologic Examination

• Drug Susceptibility Testing

• Radiographic Exam

• Sputum smear-negative patient

Module Overview

International Standards 1, 2, 3, 4, 5, and 18

Learning Objectives

At the end of this presentation, participantswill be able to: List the steps involved in diagnosing

tuberculosis Describe the role of sputum smear

microscopy in the diagnosis of tuberculosis

Recognize the role of culture and drug sensitivity testing in the diagnosis and management of tuberculosis

Case Finding

Rapid, accurate diagnosis is essential for individual and public health

Despite technical advances, clinical acumen with a high index of suspicion remains vital to the diagnosis of tuberculosis

THINK TB

Where can you conduct case finding activities?

Opportunities for Case Finding

TB Chest Clinics Hospitals (Public) Public Health Clinics Voluntary Counselling

and Testing (VCT) clinics

Prevention of Mother to Child Transmission (PMTCT) clinics

Correctional facilities (prisons, jails)

Drug Rehab Centres HIV Care facilities Private medical clinics Occupational Health

facilities Long term care

facilities and shelters

Steps in Diagnosing TB

Medical History Bacteriologic

examination TB Culture and Drug

Susceptibility Testing Radiographic exam Other examinations

based on site(s)/location(s) involved

Medical History

Known exposure to a person with infectious pulmonary TB

Symptoms of TB disease and onset Previous treatment for latent TB infection

or active TB disease Risk factors for developing TB disease Other medical conditions that might affect

treatment approach

What are the signs and symptoms of tuberculosis?

Standard 1: Prolonged Cough

All persons with otherwise unexplained productive cough lasting two-three weeks or more should be evaluated for tuberculosis

International Standards for Tuberculosis Care, 2009

Prolonged Cough

Think TB: Prolonged Cough (2 - 3 weeks)

Cough may not be specific for TB, however, long duration raises the likelihood of TB diagnosis

This is common criterion for suspecting TB in most national and international guidelines

The likelihood of AFB smear-positive sputum increases with increasing duration of cough

Will not catch all TB cases; use best clinical judgment

“Classic” TB Clinical Presentation

Subtle onset and chronic course Chest symptoms• Cough (usually productive)• Hemoptysis• Chest pain (usually pleuritic)

Nonspecific constitutional symptoms Extrapulmonary symptoms (if involved)

Typical Systemic Symptoms

Fever in 65-80% of cases Night sweats Fatigue/malaise Anorexia/weight loss

10-20% of TB cases have no symptoms at the time of diagnosis

Clinical Presentation

Physical Examination (PE): May be normal in mild–moderate disease Lungs: rales, rhonchi; absent breath

sounds and dullness to percussion if pleural fluid is present

Extrapulmonary (site specific): adenopathy, skin lesions, bone tenderness, neck stiffness, etc.

The PE is most useful when assessing for non-pulmonary sites of TB

Bacteriologic Examination

All patients suspected of having pulmonary TB who can produce sputum should have at least two sputum specimens obtained for microscopic examination in a quality-assured laboratory.

When possible, at least one early morning specimen should be obtained.

Standard 2: Sputum Microscopy


Sputum Microscopy

To confirm a diagnosis of TB, every effort must be made to identify the causative agent

The AFB smear in high-prevalence areas is:• Highly specific for TB

• Most rapid method for determining TB diagnosis

• Identifies those at greatest risk of dying from TB

• Identifies those most likely to transmit disease

Mase SR, Int J tuberc Lung Dis 2007;11(5): 485-95

Average yield of single early morning specimen: 86.4%Average yield of single spot specimen: 73.9%

Performance of Sputum Microscopy

Specimen Number

Incremental Yield (of all smear positive)

Incremental Sensitivity

(of all culture positive)

1 85.8% 53.8%

2 11.9% 11.1%

3 2.4% 3.1%

Total 100% 68.0%

Culture & Drug Susceptibility Testing

Obtaining culture anddrug susceptibilitytesting (DST) offerssignificant advantagesin the diagnosis andmanagement of TB: Increases case detectionEarlier diagnosisIdentification of drug resistance

Culture: Advantages

Higher sensitivity than smear microscopy (culture can make diagnosis despite fewer bacilli in specimen)

If TB disease is suspected and sputum smears are negative, culture may provide diagnosis

Allows for identification of mycobacterial species

Allows for drug susceptibility testing

Culture: Disadvantages

Cost Technical complexity May take weeks to get results Requires ongoing quality assurance

Therefore, culture testing is more likely to be found in major referral centers. Avoid delaying appropriate TB treatment in suspicious cases while awaiting results.

Case 1

A 32 year old man presents to the clinic with complaint of cough x 1 month. He is not severely ill and can be evaluated in an ambulatory setting.

Questions:What other history do you ask him about?What other signs will you look for during your examination to aide in diagnosis?

Case 1 (2)

Patient gives further history of feeling poorly for several months now; reports weight loss (about 3-4kg) and cough has gotten progressively worse. Patient denies smoking. His brother was treated for tuberculosis last year. Patient was not evaluated for TB at that time.

Question:What laboratory tests would do you order?

Case 1 (3)

Among the results you receive, one of two sputum smears is positive for acid fast bacilli (AFB) on direct microscopy.

Question:What would you do next?

Case 1 Summary

If smear result is from a Lab with EQA: Obtain chest X-ray, order TB culture and

initiate TB treatment

Standard 3: Extrapulmonary Specimens

For all patients suspected of having extrapulmonary TB, appropriate specimens from the suspected sites of involvement should be obtained for microscopy, culture, and histopathological examination.


Pulmonary, 70%

Extrapulmonary, 21%

Both, 9%

Pleural, 18%Lymphatic, 42%

Bone/joint, 11% Genitourinary, 5%

Meningeal, 6%

Other, 12%

TB Cases by Form of Disease,United States, CDC, 2005 Peritoneal, 6%

Clinical Presentation: Extrapulmonary

Incidence/site may vary TB can involve any organ More common in HIV/TB (co-infection)

Extrapulmonary Tuberculosis

Radiographic Examination

Standard 4: Evaluation of Abnormal CXR

All persons with chest radiographic findings suggestive of tuberculosis should have sputum specimens submitted for microbiological examination.


Evaluation of Abnormal CXR

Study from India: 2229 outpatients evaluated by CXR/culture

Of 227 cases deemed TB by CXR alone• 36% had negative sputum cultures for TB

Of 162 culture-positive cases of TB• 20% would have been missed based on CXR alone

CXR alone is not enough!

Nagpaul DR, Proceedings of the 9th Eastern Region Tuberculosis Conference and 29th National Conference on Tuberculosis and Chest Diseases. 1974 Delhi, as cited in Toman’s tuberculosis.

Case detection, treatment and monitoring, 2nd Edition: World Health Organization, 2004

Chest Radiography

Purpose: Provides additional evidence to aid in diagnosis

of TB disease when only 1 sputum smear is positive in settings without an EQC laboratory

Check for lung abnormalities in people who have symptoms of TB; especially in those with HIV co-infection

Evaluate and rule out TB disease in persons with a newly positive tuberculin skin test (Mantoux)

Chest X-ray alone cannot confirm TB disease

Chest Radiography (2)

Chest X-ray findings suggestive of active PTB disease include: Acute upper lobe pneumoniaUnresolving pneumoniaCavitation, cavitary lesionPleurisy, pleural effusionLung infiltrate, especially in upper lung zonesIntrathoracic adenopathy


Chest Radiography (3)

Chest X-ray findings suggestive of previous or presumed inactive PTB include: Apical fibrosisUpper lobe fibronodular abnormalityPleural (fibro) calcificationUpper lung zone bronchiectasisThoracoplasty or partial pneumonectomyHealed primary lesion (Ghon focus/complex)

Can this be TB?

Can this be TB? Miliary TB

54-year-old man with three months of focal low-back pain

Can this be TB?

54-year-old man with three months of focal low-back pain

Can this be TB? Extrapulmonary

“Pott’s disease” Signs and symptoms of extrapulmonary TB

are site specific Sampling of extrapulmonary sites for smear,

culture, and histopathology may confirm diagnosis

Sputum Smear-Negative Patient

Criteria for diagnosis: Have sputum that is smear-negative but culture-

positive for M. tuberculosis

OR Decision by a clinician to treat with a full course

of anti-TB therapy; AND Chest X-ray consistent with TB; AND either:

• Laboratory or strong clinical suspicion of HIV infection

• Lack of response to broad-spectrum (non-fluoroquinolone) antibiotic (if HIV-negative or unknown)

Standard 5: Smear-negative Diagnosis

The diagnosis of sputum smear-negative PTBshould be based on the following criteria: At least two negative sputum smears (including

at least one early morning specimen) Chest radiographic findings consistent with TB Lack of response to a trial of broad-spectrum

anti-microbial agents (avoid use of fluoroquinolones)

For such patients sputum cultures should beobtained.


Standard 5: Smear-negative Diagnosis (2)

In persons who are seriously ill or have known or suspected HIV infection, the diagnostic evaluation should be expedited and if clinical evidence strongly suggests TB, a course of antituberculosis treatment should be initiated


TB Diagnostic Algorithm:HIV-Negative or Low Prevalence Area

Yes TB*

Any smear +

Repeat AFB smearOrder TB culture

> 1 smear +or TB culture + All smears -

CXR & medical officer’sjudgmentYes TB*

No

Rx: Non-anti TB antibioticsImprovement?

No TB

> 2 smears -

Yes

Sputum AFB MicroscopyAssess for HIV

All Pulmonary TB Suspects

TB Diagnostic Algorithm:HIV-Positive and High Prevalence

Ambulatory HIV+ TB Suspect

AFB smears/culture; DST

AFB Positive* AFB Negative *

Treat for bacterial infection and/or PCP;HIV care if positive; CPT

TB likely

Reassess for TB

Treat for TB; CPT;HIV care if positive

Clinical evaluation; CXR; TST; may repeat AFB smears/culture

TB not likely

No or poor response

Response

CPT = cotrimoxazole prophylaxis

Reassess if symptoms recur

Clinical Presentation and Diagnosis of TB

Remember: Symptoms/severity can range from none to

overwhelming Tempo of illness: ranges from indolent to fast TB can involve any organ or tissue Signs/symptoms may be both local and

systemic Consider HIV testing in the diagnostic

evaluation

TB is capable of presenting in many ways

Can this be TB?

Can this be TB?

Distribution: Any lobe involved (slight lower lobe predominance)

Air-space consolidation Cavitation is uncommon

(< 10%) Adenopathy is common

(especially in children and HIV)

Miliary pattern

Atypical pattern: Primary TB

ISTC Standard 18

All providers of care for patients with TB should ensure that persons who are in close contact with patients who have infectious TB are evaluated and managed in line with international recommendations. The determination of priorities for contact investigation is based on the likelihood that a contact:

1.Has undiagnosed TB

2.Is at high risk of developing TB if infected

3.Is at risk of having severe TB if the disease develops

4.Is at high risk of having been infected by the index case

ISTC Standard 18 (2)

The highest priority contacts for evaluation are:

Persons with symptoms suggestive of tuberculosis

Children aged <5 years

Contacts with known or suspected immunocompromise, particularly HIV infection

Contacts of patients with MDR/XDR tuberculosis

Other close contacts are a lower priority group

Contact Investigation

There is a high likelihood that a person with smear-positive PTB will transmit tuberculosis. Therefore, prompt and thorough contact investigation is essential for the control of TB

Contact investigations should start with the persons most likely to be infected (those who most frequently come in contact with the person who has infectious TB)

Contact Investigation (2)

Actively seeking out and evaluating contacts to persons with smear-positive PTB is an important TB control strategy for two reasons:

• It identifies persons with previously undetected tuberculosis, allowing initiation of treatment and halting further transmission

• It identifies persons with TB infection who would benefit from isoniazid preventive therapy (IPT) to prevent future TB reactivation

Case Finding and Diagnosis of TB

Summary: A prolonged duration of cough should raise TB

suspicion and trigger a diagnostic evaluation TB risk factors and exposure increase level of

suspicion AFB smear in high-prevalence areas is highly

specific and most rapid tool for diagnosing TB Radiographic patterns may help in TB

diagnosis if suspicion high and AFB smear is negative, but a radiograph alone is not enough to make diagnosis

* Abbreviated versions

Summary: ISTC Standards Covered*

Standard 1: Unexplained productive cough lasting 2-3 weeks or more should be evaluated for tuberculosis.

Standard 2: All TB suspects should have at least 2 sputum specimens obtained for microscopic examination (at least one early morning specimen if possible).

Standard 3: Specimens from suspected extrapulmonary TB sites should be obtained for microscopy, culture, and histopathological exam.

Summary: ISTC Standards Covered* (2)

Standard 4: All persons with chest radiographic findings suggestive of TB should have sputum specimens submitted for microbiological examination.

Standard 5: The diagnosis of smear-negative PTB should be based on the following: at least two negative sputum smears (including at least one early morning specimen); CXR finding consistent with TB; and lack of response to broad-spectrum antibiotics (avoid fluoroquinolones). Obtain cultures. Seriously ill or HIV + patients should have an expedited diagnostic evaluation and if there is strong clinical evidence, treatment should be initiated.


Summary: ISTC Standards Covered* (3)

Standard 18: All providers of care for patients with TB should ensure that persons who are in close contact with patients who have infectious TB are evaluated and managed in line with international recommendations. The highest priority contacts for evaluation are:

Persons with symptoms suggestive of tuberculosis Children aged <5 years Contacts with known or suspected immunocompromise,

particularly HIV infection Contacts of patients with MDR/XDR tuberculosis Other close contacts are a lower priority group


Think TB

Additional Cases

Can this be TB?

Can this be TB?

Distribution Apical / posterior segments

of upper lobes Superior segments of lower lobes Isolated anterior segment

involvement is unusual (think M. avium complex or other disease)

Typical Pattern: Reactivation, Post-primary TB

Reactivation/Post-primary TB

Patterns of disease Air-space consolidation Cavitation, cavitary

nodule Endobronchial spread Miliary Bronchostenosis Tuberculoma Pleural effusions

Can this be TB?

Can this be TB?

Findings suggestive of prior TB

Ca+ granuloma – Ghon lesion Ca+ granuloma and hilar node

calcification – Ranke complex Apical pleural

thickening Fibrosis and

volume loss

case finding and diagnosis

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