Data and safety monitoring board (DSMB)		A committee of independent clinical research experts not involved in the conduct of a clinical trial. They review interim data while the trial is in progress to ensure the safety of participants and the validity and integrity of the data. Based on their reviews, a DSMB makes recommendations to the trial sponsor regarding continuation of the trial.
Diagnostics		The science and practice of diagnosis of disease. The primary diagnostic test for tuberculosis in disease-endemic developing countries is sputum smear microscopy.
Directly observed therapy, short course (DOTS)		An internationally recommended TB control strategy combining five elements: political commitment; microscopy services for diagnosis; drug supplies; surveillance and monitoring systems; and use of highly efficacious regimes with direct observation of treatment.
DNA (deoxyribonucleic acid)		The genetic material of all cellular organisms and most viruses. DNA carries the information needed to direct protein production. In most cellular organisms, DNA is organized on chromosomes located in the nucleus of the cell.
DNA vaccines		An investigational vaccine technology in which one or more genes from a disease-causing pathogen coding for specific antigen(s) are injected into the body, where they are expressed to produce antigen(s). These then stimulate immune responses in the recipient. The technology is promising for producing simple, inexpensive and heat-stable vaccines.
Double-blind study		A clinical trial in which neither the study investigators and staff nor the study participants know which participants are receiving the investigational vaccine and which are receiving a placebo or control vaccine. Double-blind studies are used to minimize bias and produce the most objective results.
Droplet nuclei		Very small droplets (1 to 5 microns, or thousandths of a millimeter, in diameter) that are expelled when a person with infectious TB coughs or sneezes. These droplets are vectors for infection when they are inhaled by another person and transported deeply into their lungs. Thus inhaled, they are responsible for person-to-person transmission of Mycobacterium tuberculosis. They can remain suspended in the air for several hours, depending on the environment.