Final answer:
A positive PPD (purified protein derivative) test for tuberculosis (TB) is not a cause for deferral.
Step-by-step explanation:
A positive PPD (purified protein derivative) test for tuberculosis (TB) is not a cause for deferral. A positive PPD test indicates that the patient has been exposed to the TB bacteria and is showing a cellular immune response to it. Therefore, it does not pose a risk of systemic mycosis, sepsis, or syphilis, which are all potential causes for deferral.