Comparison of the Abbott m 2000 RealTi m e CT Assay and the Cepheid GeneXpert CT/NG Assay to the Roche Amplicor CT Assay for Detection of Chlamydia trachomatis in Ocular Samples from Tanzania

Abstract

The GeneXpert CT/NG assay (GeneXpert) and the Abbott m2000 RealTime CT (m2000) assay were compared to Amplicor for detecting ocular Chlamydia trachomatis. Discordant specimens were tested by the Aptima CT assay. The m2000 assay sensitivity was 100% (95% confidence interval [CI], 90% to 100%), and specificity was 98.46% (95% CI, 95.2% to 99.2%); GeneXpert sensitivity was 100% (95% CI, 90% to 100%), and specificity was 100% (95% CI, 98.1% to 100%). The m2000 and GeneXpert assays appear to perform as well as the Amplicor assay. The leading infectious cause of preventable blindness worldwide is trachoma, which occurs in resource-limited countries, including sub-Saharan Africa, and is caused by repetitive and untreated ocular Chlamydia trachomatis infections (1, 2, 3). The current reservoir of active disease and infection is in children; in villages where such infections are hyperendemic, C. trachomatis infections have been found in children who have been treated at least once though mass drug administration (MDA) (1, 4). PCR is considered to be the current gold standard test, although there is no defined gold standard test for ocular C. trachomatis infections (5, 6). The Roche Amplicor CT PCR assay (Roche Diagnostics, Indianapolis, IN) has been used in major trials to monitor infection following MDA (7). Testing for C. trachomatis infection is often difficult in regions associated with trachoma; the laboratory infrastructure is often deficient or nonexistent, and there is often a lack of trained personnel, equipment, funding, and cleanliness of testing areas. The Cepheid GeneXpert CT/NG Research Use Only (RUO) assay (GeneXpert) (Cepheid Inc., Sunnyvale, CA) is a rapid test designed to produce results relatively quickly, with little hands-on time required, and could be useful in areas where trachoma occurs. We evaluated the Abbott m2000 RealTime CT (m2000) assay (Abbott Molecular Diagnostics, Des Plaines, IL) for detection of C. trachomatis in ocular specimens from Tanzania as a means to reduce turnaround time for results and increase sample throughput. A first-generation GeneXpert CT/NG assay (GeneXpert) was subsequently evaluated as a potential method for testing ocular specimens in the field to expedite provision of immediate treatment of C. trachomatis ocular infections, pending demonstration of its performance in a laboratory setting.Duplicate ocular swab specimens (n ϭ 304) from the same eye were collected from children in Tanzania for the detection of C. trachomatis infection; collection was performed as previously described (8). Samples were shipped frozen in a dry state to the Johns Hopkins University (JHU) Research Laboratory in Baltimore, MD, and stored at Ϫ80°C until testing. Swabs were rehydrated with 1 ml of sterile molecular analysis-grade diethylpyrocarbonate (DEPC) water (Quality Biological, Inc., Gaithersburg, MD). One set of the duplicate specimens was tested by Amplicor (Roche Diagnostics) and GeneXpert (Cepheid) and, for discordance testing, by the GenProbe-Aptima CT (ACT) assay (Gen-Probe Hologi...

High prevalence of sexually transmitted infections in pregnant adolescent girls in Tanzania: a multi-community cross-sectional study

“…Dangers to babies of pregnant women with untreated gonorrhoea and chlamydia include prematurity (both infections), conjunctivitis and pneumonia (chlamydia) and ophthalmia neonatorum and disseminated infection (gonorrhoea). With the development of rapid CT/NG test capability using the Gene Xpert format25 and the increasing dispersal of these machines in resource-limited settings, same-day testing and treatment for these infections is becoming an achievable goal to improve both maternal and child health. As an illustrative model, the implementation of routine point-of-care syphilis testing for pregnant women in sub-Saharan Africa has been recently estimated to reduce stillbirths, neonatal deaths and congenital syphilis cases by 64 000, 25 000 and 32 000 per year, respectively, and to reduce disability-adjusted life-years by 2.6 million 26.…”

Field Evaluation of the Cepheid GeneXpert Chlamydia trachomatis Assay for Detection of Infection in a Trachoma Endemic Community in Tanzania

“…The ocular specimens sent to JHU were processed for the detection of CT using the AMPLICOR CT/NG test (Roche Molecular Diagnostics, Indianapolis, IN) according to manufacturer [16] instructions. DNA extraction of the specimens was performed on the Roche MagNA Pure LC extraction robot with 200 uL of sample resulting in 100 uL of DNA elute using the MagNA Pure LC DNA Isolation Kit I (Roche Diagnostics).…”

“…A study in the International Chlamydia Research Laboratory at Johns Hopkins compared ocular swabs tested with the Amplicor CT assay (Roche Molecular Diagnostics, Indianapolis, IN), Abbott m 2000 RealTi m e CT Assay ( m 2000) (Abbott Molecular Diagnostics, Des Plains, IL) and a new test, Cepheid GeneXpert CT/NG Assay (GeneXpert) (Cepheid, Sunnyvale, CA), and found excellent concordance [16]. The GeneXpert has already been shown to be sensitive and specific in identifying genital chlamydia infections [17], and to be easy to use in a field setting.…”

Comparative Evaluation of 2 Nucleic Acid Amplification Tests for the Detection of Chlamydia trachomatis and Neisseria gonorrhoeae at Extragenital Sites

“…15–17 We evaluated the performance of the Xpert ® CT/NG assay for use with extragenital specimens at a sexual health clinic in Hollywood, CA.…”