  In randomized studies evaluating treatments for tuberculosis (TB),
individuals are scheduled to be routinely evaluated for the presence of TB
using sputum cultures. One important endpoint in such studies is the time of
culture conversion, the first visit at which a patient's sputum culture is
negative and remains negative. This article addresses how to draw inference
about treatment effects when sputum cultures are intermittently missing on some
patients. We discuss inference under a novel benchmark assumption and under a
class of assumptions indexed by a treatment-specific sensitivity parameter that
quantify departures from the benchmark assumption. We motivate and illustrate
our approach using data from a randomized trial comparing the effectiveness of
two treatments for adult TB patients in Brazil.
