Professional and Linguistic Assessments Board (PLAB) Practice Exam

A positive Mantoux test is indicated by a reaction greater than what size?

1. 10 mm

2. 8 mm

3. 6 mm

4. 4 mm

The correct answer is: 6 mm

A positive Mantoux test is indicated by a reaction greater than 5 mm in individuals who are considered at higher risk for tuberculosis (TB), such as those with recent contact with TB-infected individuals, individuals with compromised immune systems, or those with certain health conditions. In the context of the question, a reaction greater than 6 mm could be considered significant, particularly for specific populations, but it is not the standard cut-off for a broad positive test interpretation. It is essential to note that depending on the patient's risk factors, the thresholds can vary; however, for the general population, a reaction greater than 10 mm is commonly accepted as indicative of a positive test. The other choice, which states greater than 4 mm, does not align with the standard indications used in clinical practice for a Mantoux test as it is too lenient a threshold for detecting potential TB exposure. Understanding these specific thresholds helps healthcare providers assess the need for further evaluation and potential treatment for tuberculosis exposure effectively and accurately.