Cough lasting > 3 weeks

Fever

Night Sweats

Weight loss

Loss of appetite

Blood in phlegm

 Unfortunately, persons with latent TB have no symptoms at all and thus may not even know they have already been infected and while they cannot spread the infection to other persons, they can develop the active disease some time down the road and thus will spread to others especially those they are in close contact with like family members and fellow workers.

Generally, persons with a weakened immune system are more at risk of latent TB reactivating to become active TB. These include persons who are organ transplant recipients, infected with HIV, persons undergoing chemotherapy. But also persons with diabetes, severe kidney disease.

Chest X-ray are usually normal in persons with latent TB. There are 2 tests that may be useful in determining if you have been exposed to TB. Mantoux tuberculin skin test (TST) and Interferon Gammas Release Assay (IGRA). Each has its advantages and disadvantages as shown in the table below:

Singapore’s Ministry of Health has made BCG vaccination compulsory to all newborn since 1957 for the purpose of of preventing more serious form of childhood TB such as TB infecting the brain. However, the vaccine has not been found to be effective in preventing TB in the lungs. In view of the fact that most Singapore-born persons have received at least 1 if not 2 doses of the vaccine, IGRAs tests like TB-Gold Quantiferon test may be more appropriate given the fact that it’s results are not affected by previous BCG vaccination. More specifically, the results from IGRAs tests do not become falsely positive due to previous BCG vaccination.

 In addition, IGRAs like TB-Gold Quantiferon test only requires blood sample from you and the testing is completed in 1 single doctor’s visit, TST test requires a tiny nick to be on the skin on your arm causing some discomfort and requires you to visit the doctor’s office again in 48-72 hours after the initial visit. Also with TST, the person interpreting the test results needs to be properly trained in order for the result to be accurate whereas for IGRA test the result is interpreted by a computer.

Although you may not currently have any symptoms if you have latent TB and thus you cannot spread it to others but in your lifetime you have a 10% chance of developing into active TB and the risk increases if your immune system becomes low at any point of time.

You can greatly reduce the risk of developing active TB by testing and if tested positive you can go on treatment. 

If you believe you are at risk of having latent TB and would like to undergo testing, please visit your doctor to discuss further.