New technologies in the diagnosis of tuberculosis.

Classic methods for laboratory diagnosis of tuberculosis are time consuming, and resulting delays can adversely affect patient care and tuberculosis control. Newer radiometric culture methods can significantly reduce the time required for detection of Mycobacterium tuberculosis. DNA probe assays and high-performance liquid chromatography of mycolic acids allow identification of isolates in a few hours, and use of these methods is strongly encouraged. A new generation of rapid methods based on techniques of molecular biology will eventually allow direct detection and identification of mycobacteria in clinical samples. These methods use rapid nucleic acid amplification techniques, such as the polymerase chain reaction (PCR), rather than growth of cultures to increase the sensitivity of detection. Assays of this type are currently being evaluated in formal trails. Recent analysis of the mechanisms of drug resistance in M tuberculosis may allow the development of assays for direct detection of drug resistant strains at the genetic level. A luciferase reporter mycobacteriophage assay offers an alternate means for rapidly assessing drug resistance. This assay measures the activity of the drug rather than the genetic basis for resistance. DNA fingerprinting methods have provided the means for distinguishing strains for epidemiological purposes. These new approaches will have a dramatic impact on our ability to rapidly and accurately diagnose tuberculosis.