Nonculture methods for diagnosis of chlamydia trachomatis genital infection : emphasis on the newly developed ligase chain reaction

The first non culture tests for diagnosis of Chlamydia trachomatis infection involved demonstration of inclusions in epithelial cell specimens. With the introduction of culture methods, it was recognised that this cytologic procedure is relatively insensitive. Isolation became accepted as the method of choice for diagnosing Chlamydial infection, but because of the obligate intracellular nature of Chlamydial growth, tissue culture systems were required and this restricted access to Chlamydial diagnostics as cell culture facilities were not widely available. Soon after their introduction, antigen detection methods became very popular. They greatly improved access to Chlamydia diagnostics. The first procedure to be introduced was a direct fluorescent antibody (DFA) technique. It was particularly useful because it restricted the number of specimens that could be tested and required expensive microscopes and well trained microscopists. It is generally considered that DFA is approximately 75-85% sensitive in detecting Chlamydial infection of the cervix and less sensitive with male urethral specimens. The comparison here is with isolation in cell culture as the gold standard, and it must be recognised that cell culture is seldom more than 80-90% sensitive.