Three years of using Aptima Combo 2 (AC2) transcription-mediated amplification for gonorrhoea in a district hospital genitourinary medicine clinic shows it to be superior to culture and has a specificity of almost 100%

Abstract

Sir: The paper by Wilson et al. 1 on the relation between oestradiol levels and bacterial vaginosis (BV) provides further evidence for an hormonal influence in this condition. In 1996, or thereabouts, Phillip Hay and I made the suggestion that sex hormone changes might be involved in the aetiology of BV. 2 This was prompted not only by BV being noted, in observations over the course of a menstrual cycle or longer, to occur often in the first part of the cycle, as mentioned by Wilson et al., 1 but also by the results of experiments in mice. In such female animals, subcutaneous administration of oestradiol produced a BV-like picture in Gram-stained vaginal smears through multiplication of the endogenous vaginal bacteria. 3 In addition, this hormone was the key factor in promoting vaginal colonization by Mycoplasma hominis, ureaplasmas and Neisseria gonorrhoeae after their experimental inoculation. 4 -6 On the other hand, progesterone was the hormone that stimulated Chlamydia trachomatis and M. genitalium to grow in mice, oestradiol having no effect whatsoever in promoting growth of these microbes. 7,8 It is not difficult to see, however, that the patterns of hormonal effects are different in women from those in mice. In women high levels of oestradiol are associated with a normal vaginal flora and low levels with an abnormal flora, whereas mice given this hormone develop a BV-like picture and a susceptibility to some organisms, which otherwise is non-existent. The picture is BV-like in the sense that there is proliferation of endogenous murine vaginal bacteria, many adherent to epithelial cells, which, of course, are quite different from the bacteria found in the human vagina. Also different is the vaginal eco-system in women and mice. In women, the healthy vagina is dominated by acid-producing lacto bacilli causing the pH to be less than 4.5, rising to 7.0 or more in subjects with BV. In mice, lactobacilli are sparse and the pH is normally 7.4 (range 6.6-8.5) and not significantly different in mice given oestradiol, that is 7.36 (range 6.5-8.6), or progesterone, namely 7.2 (range 6.4-7.7). In addition, the nature of the cellular composition is somewhat different in women during the menstrual cycle than in mice during the oestrous cycle. In the former, a rising level of oestrogen is associated with proliferation of the vaginal stratified squamous epithelial cells and the surface cells become large and flattened with small or absent nuclei (cornification); in the second half of the cycle, with increasing progesterone, there is mucification of the squamous epithelium with large clear nucleated cells. Only at the end of the cycle, during menstruation, are erythrocytes and leucocytes seen. In the murine reproductive cycle, the oestrogenic phase is defined by squamous epithelial cells, some nucleated (early oestrous stage) or exclusively non-nucleated (oestrous stage) and a di-oestrous phase, stimulated by progesterone, characterized by an infiltration of polymorphonuclear leucocytes to the exclusion of epithelial cells...

Management of cases testing positive for gonococcal infection in a community-based chlamydia screening programme

“…Findings showed a lower PPV for AC2 compared with research-based clinical studies using rigorous re-test practices 8. Similar to findings here, Lavelle and colleagues showed that AC2 tests defined as ‘false positives’ had had contact with gonorrhoea-positive partners 9.…”

Concordance between nucleic acid amplification technique and culture for the diagnosis of gonorrhoea

“…This study differs from the findings of previous studies, which found a concordance rate of 80 -92%. 1,12 These studies are taken in areas of much lower prevalence of gonorrhoea, which may contribute to the greater discordance rate.…”

Performance of the cobas CT/NG Test Compared to the Aptima AC2 and Viper CTQ/GCQ Assays for Detection of Chlamydia trachomatis and Neisseria gonorrhoeae

“…The CDC STD Laboratory Diagnosis Guidelines recommend screening using highly sensitive and specific nucleic acid amplification assays (NAATs) (4), confirming that this class of testing is now considered the standard for the diagnosis of these infections. NAATs have been commercially available for the last 2 decades, and evidence of their performance characteristics is widely available (6,7,(10)(11)(12)(13)(14)(15)(16)(17). As chlamydia and gonorrhea screening programs continue to expand to meet the health care coverage benchmarks described by the U.S. Preventive Task Force (USPTF), the CDC (5), and the Healthcare Effectiveness Data and Information Set (HEDIS), clinical diagnostic laboratories will experience increased volumes.…”