Effect of Endocervical Specimen Adequacy on Ligase Chain Reaction Detection of Chlamydia trachomatis

Abstract

Several studies have demonstrated that the sensitivity of a commercially available PCR test for the detection of Chlamydia trachomatis (Roche Diagnostics) is affected by the cellular quality of the endocervical swab specimens. The cellular adequacies of 1,633 female endocervical swab specimens were assessed and compared with the results of C. trachomatis detection obtained by ligase chain reaction (LCR; Abbott Laboratories). Specimen adequacy studies and LCR were performed with samples from the same swab, after demonstration of the stability of human epithelial cells in LCR transport medium. Prior to heat treatment of the swab specimen, an aliquot was removed and cytocentrifuged onto a slide. Cell spots were stained and examined at ؋400 magnification for endocervical (columnar epithelial or metaplastic) cells and erythrocytes. The overall rate of positivity of the LCR was 6.5% (106 of 1,633 specimens) with pooled specimens (pools of 4 specimens each; reduced cutoff). Of the 1,633 specimens examined, 655 (40.1%) were found to contain one or more endocervical cells. The rate of positivity for C. trachomatis was 10.8% (71 of 655 specimens) among specimens containing endocervical cells, whereas it was 3.6% (35 of 978 specimens) among specimens lacking endocervical cells (P < 0.0001). There was no linear trend between the rate of positivity for C. trachomatis and the number of endocervical cells (P ‫؍‬ 0.24). The rate of positivity for C. trachomatis was 5.4% (8 of 147 specimens) among specimens containing large numbers of erythrocytes (>100 per high-power field), whereas it was 6.6% (98 of 1,486 specimens) among specimens containing less than 100 erythrocytes per high-power field (P ‫؍‬ 0.59). These results show that the sensitivity of the Abbott C. trachomatis LCR test is affected by the presence of endocervical cells. Additionally, they indicate that the presence of a single endocervical cell is as good an indicator of specimen adequacy as the presence of many endocervical cells. The presence of a large number of erythrocytes was not associated with an increased rate of sensitivity of the LCR.Chlamydia trachomatis is the most common bacterial sexually transmitted organism in the United States, with an estimated annual incidence of infections with this organism of 3 million to 4 million (3, 4). A variety of commercially available test methods exist for the detection of C. trachomatis infections, including cell culture, antigen detection enzyme immunoassay, direct fluorescent-antibody assay, nonamplified nucleic acid hybridization tests, and nucleic acid amplification tests. The analytical and clinical sensitivities of these methods vary greatly (2). In addition, the sensitivities of direct fluorescent-antibody assay, enzyme immunoassay, and nucleic acid hybridization tests have been shown to be affected by the cellular adequacy (presence of columnar epithelial or metaplastic [endocervical] cells or large numbers of erythrocytes [more than 100 per high-power microscopic field]) of female endocervical swab specimens ...

Effect of Endocervical-Specimen Adequacy on Detection of Chlamydia trachomatis by the APTIMA COMBO 2 Assay

“…Our results differed from earlier studies with amplification tests, PCR (10,18), and ligase chain reaction (12), which concluded that cellular adequacy was a determining factor when testing for the presence of C. trachomatis. We were able to detect C. trachomatis even when the specimen was graded as inadequate, based on the same measurement of cellular adequacy.…”

2015 UK national guideline for the management of infection with Chlamydia trachomatis

“…VVS has a sensitivity of 96–98% and can be either taken by the patient or a healthcare worker (HCW). Several studies indicate that VVS sensitivities are higher than those of cervical swabs, 82–85 as they pick up organisms in other parts of the genital tract. Self-taken VVS are more acceptable to women than urine or cervical specimens.…”

Frequency of sexually transmitted diseases and main methodological implications

“…Pochi i test di diagnostica basati sull'amplificazione della regione codificante per le oncoproteine E6 ed E7, in grado di rilevare anche il DNA virale integrato, forma altamente frequente nei carcinomi e nelle lesioni intraepiteliali di alto grado (33). Pochi i lavori in letteratura che misurano la cellularità del campione, parametro importante per la valutazione dell'idoneità del prelievo nella diagnostica molecolare soprattutto per la rilevazione di patogeni intracellulari quali HPV e C. trachomatis (7,27,47). Tale parametro, presente almeno qualitativamente nella lettura del Pap-test, non viene più valutato in un test molecolare quando eseguito su un prelievo dedicato.…”