**1. Introduction**

The Chlamydiaceae family is an obligate intracellular bacterial member. Only the genus *Chlamydia* has 9 species distributed in vertebrates that cause serious effects on human health. The history of *Chlamydia* infection in humankind dates back to 4000 years [1]. *Chlamydia trachomatis* is one of the most common sexually transmitted pathogens worldwide. A *C. trachomatis* infection can cause urethritis, cervicitis, proctitis, and conjunctivitis, depending on the anatomical site of the infection. 50% of men and 70% of women are asymptomatic [2]. When CT infection is not treated, it can cause infertility in men and women, such as epididymitis and pelvic inflammatory disease [3]. If *C. trachomatis* infection increases, it can cause endometriosis of the female upper genital tract, pelvic inflammatory disease and tissue scarring, infertility, ectopic pregnancies, and fibrotic disorder and is also potentially associated with cervical and uterine cancers [4].

Culture methods were first allowed as standards in the 1970s and were developed using McCoy cells. The specificity of this method, originally developed for trachoma and lymphogranuloma venereum (LGV), was 100%, but the overall sensitivity was estimated to be 40–85% lower due to laboratory sensitivity, sampling errors, and variable laboratory standards. In the 1980s, there was a return to the fashion for microscopic identification without culturing using a technique known as direct fluorescence testing, and testing was performed by binding specially produced antibodies to specific sites on the outer membrane of *Chlamydia*. It was used because it was quick and relatively inexpensive, with results being more variable compared to other methods, influenced by many factors, including the recognition of three strains or serotypes of *C. trachomatis*. Because of the revolutionization of the laboratory diagnosis of all diseases using monoclonal antibodies, thanks to many of the advances in molecular biology developed by new biotechnology companies, there are new tests for antibodies (complement fixation and microimmunofluorescence) and new antigen tests (direct fluorescence test and enzyme immunoassay). All were compared to the gold standard of cell culture, but there was growing doubt that this was better than any of the newer tests. In the 1990s, new assays using new DNA technologies, particularly the polymerase chain reaction (PCR) technologies, became available to develop nucleic acid amplification assays (NAATs). In these tests, fragments of *Chlamydia* DNA extracted from clinical samples were amplified in repeated cycles to produce samples large enough for colorimetric evaluations. The first such test was introduced by Roche in 1993. *AMPLICOR C. trachomatis*. An evaluation by doctors in Bordeaux the following year found it to have a sensitivity of 95.3% and a specificity of 100%, concluding that it was superior to culture methods. This was followed by other tests from other companies [1, 5].

Recent taxonomic developments based on 16S and 23S rRNA gene sequences, along with the development of molecular tests, have divided the Chlamydiaceae family into two genera and nine species, including 5 species found to infect humans [6]. Over time, new variants of *C. trachomatis* have emerged, and new test techniques that are inexpensive and easily applicable may emerge to identify them [7]. *Chlamydia* is the most commonly diagnosed bacterium among sexually transmitted diseases [8].

Infection diagnosis rates continue to increase in the developed world. Because *Chlamydia* is largely asymptomatic, screening is the most basic way to detect cases and reduce transmission [9].
