Communicable Diseases Module: 14. Diagnosis and Treatment of Tuberculosis

Study Session 14  Diagnosis and Treatment of Tuberculosis

Introduction

In this study session you will learn about methods for diagnosis of tuberculosis, be introduced to different categories of patient with TB and also learn about treatment of tuberculosis with drugs, including the major side-effects of these medications. Even though you are not the person with responsibility for diagnosing and prescribing anti-TB drugs, having this information will enable you to swiftly identify and refer people suspected of having TB and ensure there is follow-up for confirmed cases. You will also learn more about the main method of diagnosis of TB, which is sputum examination under a microscope, and other supportive measures like chest X-ray, which is likely to help diagnosis of individuals who are smear-negative.

Your role is to make sure that every person diagnosed with TB takes the recommended drugs, in the right combinations and at the right time, for the appropriate duration. The best way to achieve this is for you to watch each patient swallow the drugs. This is called Directly Observed Treatment, Short Course (DOTS) and was introduced in Study Session 13. Directly observed treatment can take place at a hospital, health centre or health post, the patient’s workplace or home. If drugs are taken incorrectly or irregularly, the patient will not be cured and drug resistance may arise. To a large extent, the success of TB treatment by drugs depends on your effectiveness in overseeing the patient’s adherence to the treatment.

Learning Outcomes for Study Session 14

When you have studied this session, you should be able to:

14.1  Define and use correctly all of the key words printed in bold. (SAQs 14.1, 14.2 and 14.3)

14.2  Describe methods used to diagnose tuberculosis and the different types of case definitions. (SAQ 14.2)

14.3  Describe different treatment categories used to treat tuberculosis. (SAQs 14.2 and, 14.3)

14.4  Describe the main drugs used to treat tuberculosis and the processes that help you ensure patients are following the correct treatment schedules. (SAQ 14.3)

14.5  Describe the potential side-effects associated with the drugs used to treat tuberculosis and explain how such side effects are managed. (SAQ 14.4)

14.1  Diagnostic methods

In Study Session 13 you learnt about the clinical symptoms of TB. They are a cough for two or more weeks, spitting up blood in the sputum, weight loss, fever or night sweats for three or more weeks, fatigue, and loss of appetite, chest pains or difficulty breathing.

If you ask the right questions and make the right observations, you will be able to identify those individuals who you suspect of having TB. What to look for depends on the type of TB involved. The key symptoms of both forms of TB are summarised in Box 14.1.

We will now describe in more detail different methods used to diagnose tuberculosis and other procedures that are used to diagnose extra-pulmonary tuberculosis (EPTB). Diagnosis of tuberculosis is made at health centres and hospitals, but you will make a vital contribution by identifying those individuals who may be infected with TB and referring them for investigation. Part of your role is to provide information and counsel those who are about to undergo diagnostic investigation and treatment.

14.1.1  Microscopic examination of sputum smears

Figure 14.1  A health professional is examining a sputum smear under a microscope.

Sputum microscopy is the most efficient way of identifying a tuberculosis infection. It is the primary tool used for diagnosing TB and for monitoring the progress of treatment until the patient is cured. You are expected to oversee the collection of sputum samples during initial diagnosis, and at various times during drug treatment to monitor the effectiveness of the treatment.

You will recall from Study Session 13 that three sputum samples will be collected over two consecutive days, and that one of the sputum samples is collected in the morning. The samples are sent to a laboratory and Figure 14.1 illustrates a health professional examining a sputum smear using a microscope. The smear is treated with chemicals that reveal the presence of TB bacteria and these can be seen using a microscope (they cannot be seen with the naked eye). The examined specimens are classified as being either smear-positive pulmonary TB or smear-negative. However, you should know that a smear-negative result could either mean the patient has TB but it is not showing in the sputum, or that the person does not have TB.

An example of a positive smear, seen under a microscope, is shown in Figure 14.2. The smear has been stained with chemicals to reveal the presence of TB bacteria (they appear as purple rod-shaped bacteria).

Figure 14.2  The photograph shows you what the health professional sees under the microscope and is an example of a smear-positive sputum specimen. (Photo courtesy of the WHO; ‘The Natural History of Pulmonary Tuberculosis, Facilitator Guide’, 2001).

A diagnosis of TB is made if at least two out of the three sputum smears are positive for TB bacteria. TB is also confirmed if one sputum specimen is positive for bacteria, and there is also evidence of abnormalities in a chest X–ray. Finally, in people living with HIV (or in the presence of a strong clinical suspicion of HIV infection), only one positive smear result is necessary to make a diagnosis of smear-positive pulmonary TB.

14.1.2  Chest X-ray

Chest X-ray is another tool used in diagnosing TB. It is particularly important when diagnosing TB in individuals who are smear-negative for the TB bacteria or who are unable to produce sputum. It is also an important diagnostic tool for those persons who may have extra-pulmonary tuberculosis; such individuals may not be able to produce sputum and should be referred to the doctor/clinician for a chest X-ray. It is also possible to have EPTB and a normal chest X-ray.

14.1.3  TB culture from sputum

Culturing of TB bacteria from a sputum sample in the laboratory is very expensive and takes several weeks to produce a result; however it is a very sensitive and highly specific tool. It plays a key role in identifying the type of drug-resistant TB found in a patient, such as those patients who are not responding to treatment as well as expected. Culture with Drug Sensitivity Testing (DST will be covered in Study Session 16) takes even longer; but provides crucial information about which antibiotics will kill the bacteria isolated from the patient. You should send patients for TB culture and DST if they are suspected of drug-resistance.

14.1.4  Biopsy

Biopsy is an important tool used to diagnose extra-pulmonary TB. It is the removal and examination of tissues from the living body to determine the existence or cause of a disease. It involves the microscopic examination of a small specimen of tissue extracted from the patient’s body. It is particularly useful for diagnosing extra-pulmonary TB in the lymph nodes and joints, as well as other affected organs. It can also be used to confirm pulmonary TB by sampling lung tissue in smear-negative suspects. Again, only doctors and clinicians are allowed to request this type of examination to diagnose TB.

14.2  Treatment of tuberculosis

The main objectives of anti-TB treatments include: to cure TB patients (by rapidly eliminating most of the bacteria), to prevent death or organ damage from active TB, to prevent relapse of TB (by eliminating the inactive bacteria), to prevent the development of drug resistance (by using a combination of drugs) and importantly to decrease TB transmission to others.

14.2.1  Classifications of TB and treatment categories

Classifications of TB cases are based on the following factors and you will see these terms used when cases are confirmed:

• organ involved: pulmonary or extra-pulmonary
• sputum result: smear-positive or smear-negative
• history of TB treatment: new or previously treated or relapsed
• severity of the disease: severe or not severe (covered later in this study session).

14.2.2  Definition of types of TB cases

You are already aware that a ‘case of TB’ is an individual in whom tuberculosis has been confirmed by microscopic examination, or diagnosed by a clinician or medical doctor.

However, there are several different types of TB cases (in other words different case definitions) and these are based on the smear result, history of previous treatment and severity of disease. These different case definitions are listed in Table 14.1, from which you’ll also see that if a patient does not fall into any of the main types, they are registered as ‘other’.

Knowing these different case definitions will help in your recording and reporting of cases, as well as giving you important information about the infectiousness of the patient, the risk of drug resistance, and where there is a need for follow-up of patients.

14.3  Patient categories and treatment regimens

In order to establish treatment priorities, the WHO recommends that TB patients should be classified into four categories, as shown in Table 14.2. Patients are started on anti-TB drugs according to their category.

Always keep in mind that patients with severe forms of EPTB may come to you with the types of symptom mentioned in Study Session 13, Table 13.2 — perhaps with TB affecting the lining of the brain (TB meningitis) or the kidney (renal TB) or the spine (spinal TB). You must refer such patients to the hospital for proper management because they need additional medication and/or special care. Disseminated TB is often used to describe TB involving two or more organs or tissues of the body and it is considered as one of the severe forms of TB.

14.3.1  Treatment regimens for different TB categories

If you are already a health worker, you will be familiar with the types of anti-TB drugs used in Ethiopia. However, we will teach the regimens here in detail because they may have been updated since you learned about them. The first line anti-TB drugs used are (drug abbreviation in brackets):

rifampicin (R), ethambutol (E), isoniazid (H), pyrazinamide (Z) and streptomycin (S).

These drugs are provided in combination. For instance R, H, Z and E are combined in one preparation in the proportions (RHZE 150/75/400/275 mg). Similarly, two drugs can be combined in one preparation, for example R and H are combined (RH 150/75 mg), and so are E and H (EH 400/150 mg). Some drugs are available as single drug preparations; such as ethambutol 400 mg, isoniazid 150 mg and 300 mg, and streptomycin sulphate vials (1 g). Streptomycin is administered by injection while the other drugs are taken orally. All the drugs should be taken by patients together as a single, daily dose, preferably on an empty stomach to improve drug absorption.

14.3.2  Phases of chemotherapy

The chemotherapy (drug treatment) of tuberculosis has two phases, known as the intensive and the continuation phases.

14.3.3  Treatment regimens

According to WHO recommendations and the national guidelines that apply in Ethiopia, the following treatment regimens should be used:

• Note that the number before the bracket refers to the number of months the drug is taken.

  Category I and III patients are treated in the intensive phase with combinations of four ‘first-line’ drugs: isoniazid, rifampicin, pyrazinamide and ethambutol for two months, which can be summarised as 2 (HRZE). In the continuation phase, they receive either a combination of isoniazid and rifampicin for four months 4 (HR), or a combination of isoniazid and ethambutol for six months 6 (HE).
• For Category I patients with a smear-positive sputum result after two months of intensive treatment, extend the intensive phase for an additional one month. Then follow the continuation phase as above. If a patient is still smear-positive after five months of treatment, then they need to be categorised as ‘treatment failure’ and restart treatment (Category II).
• Category II patients are treated with five drugs for the initial two months of the intensive phase: a combination of isoniazid, rifampicin, pyrazinamide and ethambutol 2 (HRZE), plus streptomycin (S); then continue with four drugs, excluding streptomycin, for an additional one month; then followed by five months of the continuation phase with isoniazid, rifampicin 5 (HR), and ethambutol (E).
• Category IV patients are treated with ‘second-line’ anti-TB drugs, which you do not need to know the details of.

These different treatment regimens are summarised in Table 14.3.

Knowing this information will enable you to understand the type of drug regimen prescribed by the doctor or clinician for different patient categories. This will help you ensure that the drug treatment is being followed correctly.

Tables 14.4 and 14.5 show the amounts of the different drugs to be administered to patients — in particular the number of tablets they take at any one time. The number of tablets depends upon the body weight of the patient. You are not expected to know the precise dosage of each drug — for example how many milligrams of isoniazid is taken when the patient takes their tablets — but it is very important for you to know the number of tablets a particular patient should be taking. So it is important to check the weight of your patients periodically and refer them to a clinician for an adjustment of drug dose if there is change in their body weight during treatment.

Table 14.4 shows the 2 (HRZE) and 6 (HE) drug regimen for categories I and III. The Ethiopian Federal Ministry of Health have now approved a move to the adoption of 4 (HR) in the continuation phase in such cases, which means four months of isoniazid and rifampicin. It may be some time before 4 (HR) becomes the standard in such cases, so in Table 14.3 both 6 (HE) and 4 (HR) are shown.

14.3.4  Anti-TB drug treatment in special situations

14.3.5  Treatment of TB patients under Directly Observed Treatment (DOTS)

As you appreciate from Study Session 13, DOTS is essential during the intensive phase of treatment (the first two to three months); it will also be needed during the continuation phase for patients with previous treatment failure who are being re-treated. Directly observed treatment ensures that the drugs are taken in the right combinations and on schedule, and that the patient continues treatment until all the doses have been taken. The health facility is the recommended place for treatment because of the ease of supervision. However, some patients live far away or do not find it convenient to come to a health facility, in which case you need to directly observe treatment at a place and time more convenient for them.

Figure 14.3  Patient under DOTS therapy. (Photo: Lung Health Image Library, World Lung Foundation)

14.4  Side-effects of anti-TB drugs and their management

14.4.1  Types and severity of side-effect

Side-effects are unwanted symptoms, discomfort or more serious adverse (harmful) consequences of drug treatment. Serious side-effects are rare in patients taking anti-TB drugs. A minority of TB patients treated with Category I or Category II regimens experience adverse side-effects categorised as:

• major adverse side-effects giving rise to serious health concerns that require the stopping of anti-TB treatment
• minor side-effects causing relatively little discomfort and often responding to simple treatment of the symptoms; they may occasionally persist for the whole period of anti-TB treatment.

Possible side-effects of the anti-TB drugs and their management are listed in Table 14.6.

In the next study session we turn to the subject of following-up patients and tracing patients who are not taking their medication.

Summary of Study Session 14

In Study Session 14, you have learned that:

1. Sputum examination should be done for all persons suspected of TB who are able to produce sputum; other diagnostic methods (chest X-ray, TB culture) support sputum examination but cannot replace it as the primary tool used for TB diagnosis.
2. Treatment for TB consists of the intensive phase (two to three months) followed by the continuation phase (four to six months). Treatment involves a combination of drugs.
3. If anti-TB drugs are taken incorrectly or irregularly, the patient will not be cured and drug-resistance may develop.
4. Health workers have to take an active role in ensuring that every TB patient takes the recommended drugs, in the right combinations, on the correct schedule, for the appropriate periods of time.
5. Anti-TB drugs are given under DOTS for the first two months for Category I and III patients, and for the whole course for re-treatment cases.
6. If a patient has major side-effects related to the anti-TB drugs, refer the patient to a clinician or hospital. If the patient has minor side-effects, reassure the patient and give advice on how to relieve the symptoms.

Self-Assessment Questions (SAQs) for Study Session 14

Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering these questions. Write your answers in your Study Diary and discuss them with your Tutor at the next Study Support Meeting. You can check your answers with the Notes on the Self-Assessment Questions at the end of this Module.