Tuberculosis
Types of Infections & Treatments
About Tuberculosis
Definition:
Tuberculosis or TB is caused by the bacteria Mycobacterium tuberculosis. This is a slow growing bacteria making the disease caused by this organism often gradual and insidious in onset. It is transmitted by close contact as well as through airborne route, hence making it an important public health disease. It is a notifiable disease under the Infectious Disease Act, Singapore.
Epidemiology:
The incidence of TB in Singapore has been falling from 307 per 100,000 (1960) to 56 per 100,000 (1987) to around 40 per 100,000 in the last few years. This was achieved through a combination of public education, aggressive contact tracing, treatment and follow-up programmes. However, we continue to see many new cases of TB in Singapore. In the local population, the majority of cases are due to reactivation of infections that occurred 20 or more years ago. This “reactivation” is due to waning immunity as we age and it is a problem which will be even more significant as we have a rapidly aging population. The successful treatment of certain diseases requiring immunosuppressive drugs such as steroids has also resulted in reactivation of TB in patients on these medications. The other contribution is from HIV infected patients and imported TB from neighbouring countries.
Clinical:
TB is a very treatable disease if detected early and provided the patient is fully compliant with the minimal treatment course of 6-9 months. Early diagnosis and treatment is very important as it prevents secondary transmission to close contacts and family members. Compliance with treatment is very important as it enhances the cure rate and prevents emergence of drug resistant strains.
As TB is airborne, the most common type of TB is TB involving the lung and constitutes almost 70% of cases notified in Singapore. However, TB can affect many other organs in the body eg brain, bones, liver, spleen, intestines, skin, testicles, uterus, ovaries, heart, lymph glands, etc.
Some individuals are more susceptible to TB than others eg.:
- Immunocompromised patients with lowered immunity – HIV patients, patients on long term steroids, chemotherapy, etc.
- Persons with chronic medical conditions eg. Diabetes, renal failure, chronic lungs, etc.
- Elderly persons due to waning of the immune system
- Healthcare workers who are constantly exposed to TB patients
- Drug addicts and homeless persons
- Persons who are malnourished
Some signs and symptoms of TB are:
- Persistent cough with/without blood
- Fever
- Night sweats
- Loss of weight
- Chest pain especially on deep breathing
Please see a doctor if you suspect TB as early diagnosis and treatment is the key to cure and control.
Diagnostic Tests:
Screening for TB is usually done if you are exposed to an index patient with pulmonary tuberculosis. Usually, the index patient will be a household contacts or work colleague sharing the same office area. First year university students who come from countries endemic with tuberculosis may also be screened for TB upon entry to the university. In addition, screening for TB may be a company policy for health care workers and expatriate staff posted to a country endemic for tuberculosis.
The tests that are usually done are the tuberculin skin test (TST) and the interferon-gamma release assays (IGRA) such as the Quantiferon TB test and the T-spot TB test. These tests indirectly measure TB infection by measuring the immune response to TB proteins. “Reactive tests” indicate that an individual has been exposed to TB. These tests are imperfect and each of them has false positive and false negative testing rates. These tests also cannot be used to determine if an individual who has been exposed to TB will progress to develop active disease. In addition, the tests cannot distinguish between latent tuberculosis and active tuberculosis.
Treatment:
Treatment is with anti-TB drugs – most of them can be taken at home and are oral drugs. Sometimes, injection drugs are used and can be administered at a clinic. For some non-compliant patients or patients with drug resistant TB, treatment in an institution or DOT ( directly observed therapy ) at a polyclinic may be required.Patients with TB need to take numerous drugs and the treatment course is 6-9 months. There is a small risk of adverse effects from such treatment and you must adhere to treatment and also follow up for monitoring of adverse effects.
Points to Note:
The only way to eradicate TB is early diagnosis and treatment. The key to complete cure is 100% compliance to the full treatment course. This is also the key to control of TB in a population.
There is a lot of research in TB in the areas of new vaccines that will make it more effective in preventing TB and newer TB drug regimens which will allow us to cure TB with a shorter course of treatment.
If you are concerned about tuberculosis, please contact your family physician or call our clinic for an appointment with one of our infectious disease physicians