American Board of Internal Medicine (ABIM) Certification Practice Exam

What criteria must a patient with active tuberculosis meet to be considered noncontagious?

1. Improvement of symptoms after one week of treatment

2. Three consecutive negative sputum cultures after at least 2 weeks of treatment

3. Clear chest radiograph after treatment

4. Absence of fever for 48 hours

The correct answer is: Three consecutive negative sputum cultures after at least 2 weeks of treatment

To be considered noncontagious in the context of active tuberculosis, a patient must demonstrate three consecutive negative sputum cultures after at least two weeks of appropriate anti-tuberculous treatment. This criterion is crucial because sputum culture is the gold standard for confirming the presence of Mycobacterium tuberculosis, the bacteria responsible for tuberculosis. The significance of achieving three negative cultures lies in the fact that it provides substantial evidence that the patient is effectively responding to treatment and that the bacilli are no longer present in quantities sufficient to pose a risk of transmission to others. This measure helps to ensure public health safety, allowing infected individuals to return to normal activities without posing a risk of infection to those around them. Other criteria, such as improvement of symptoms, absence of fever, or clear chest radiographs, while valuable indicators of clinical response and improvement, do not provide definitive proof of noncontagiousness. Symptoms can sometimes improve while bacteria are still present, and a clear chest radiograph may not reflect the current infectious status of the patient. Therefore, reliance on negative sputum cultures is a critical component of assessing whether a patient with active tuberculosis is no longer contagious.