Screening tests for<i>Chlamydia trachomatis</i>or<i>Neisseria gonorrhoeae</i>using the cobas 4800 PCR system do not require a second test to confirm: an audit of patients issued with equivocal results at a sexual health clinic in the Northwest of England, UK

Hopkins, Mark; Smith, Godfrey; Hart, Ian; Alloba, Fath

doi:10.1136/sextrans-2012-050535

Cited by 13 publications

(10 citation statements)

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“…However, it should be noted that a limitation and potential bias of this study was that the PCR and culture were, for the most part, not performed on the same sample type (i.e., PCR was performed on urine samples and bacterial culture on genital swabs). Nevertheless, our findings are supported by two recent studies which showed that the cobas N. gonorrhoeae test had lower levels of false positivity than predecessor assays (9) and does not require a confirmation test for N. gonorrhoeae in urine specimens (10). Despite recent calls to move to NAAT routinely for pharyngeal and rectal testing, it is still recommended that positive results from these sites be confirmed by supplemental assays (5).…”

Section: Discussionsupporting

confidence: 74%

“…gonorrhoeae NAAT assays, our data show that a urine specimen alone is not sufficiently sensitive (86.7%) to screen for N. gonorrhoeae in females (19,20). We have previously shown that interference from mucopurulent discharge in N. gonorrhoeae-positive patients causes failed cobas 4800 results (12), and this has also been reported by Hopkins et al (10). Most failed results can be resolved by treatment with Sputasol (1.4% DTT; Oxoid) (12).…”

Section: Discussionsupporting

confidence: 56%

“…However, the N. gonorrhoeae test was not initially reported, and culture was maintained for detection of gonorrhea. Recent studies report improved clinical and analytical specificity of the cobas 4800 N. gonorrhoeae assay over previous assays (8,9), indicating that N. gonorrhoeae confirmatory testing may not be required on some specimens (10). This study compared the cobas 4800 N. gonorrhoeae test to culture, for genital and nongenital specimens, to investigate whether its performance would be acceptable without supplementary confirmatory testing in our low-prevalence population.…”

Section: N Ucleic Acid Amplification Tests (Naats) Have Been Recommenmentioning

confidence: 99%

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Comparison of the cobas 4800 CT/NG Test with Culture for Detecting Neisseria gonorrhoeae in Genital and Nongenital Specimens in a Low-Prevalence Population in New Zealand

Bromhead¹,

Miller²,

Jones³

et al. 2013

J Clin Microbiol

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bTo assess the clinical utility of replacing microbial culture for Neisseria gonorrhoeae with a nucleic acid amplification test (NAAT), we compared N. gonorrhoeae culture with the cobas 4800 CT/NG test for 18,247 urogenital and 666 nongenital samples. For urogenital specimens, the sensitivity, specificity, and positive and negative predictive values of the cobas N. gonorrhoeae PCR were 98.7%, 100%, 95.6%, and 100%, respectively, and for nongenital specimens, the values were 100%, 99.8%, 92.9%, and 100%, respectively. In our test population, 37% (10,185) of patients tested over the study period were screened for C. trachomatis by PCR but were not screened for gonorrhea by culture. Of these, 43 were N. gonorrhoeae positive by PCR and therefore went undiagnosed. The cobas 4800 CT/NG test diagnosed 33% (n ‫؍‬ 30) more urogenital and 25% (n ‫؍‬ 3) more rectal gonorrhea infections than culture and, based on the above performance indicators, does not require supplementary testing for urogenital or rectal specimens. The ability to test noninvasive specimens (such as urine and self-taken vulvovaginal swabs) for N. gonorrhoeae will enable more patients to be screened for infection, thus offering significant positive public health benefits.

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Section: Discussionsupporting

confidence: 74%

Section: Discussionsupporting

confidence: 56%

Section: N Ucleic Acid Amplification Tests (Naats) Have Been Recommenmentioning

confidence: 99%

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Comparison of the cobas 4800 CT/NG Test with Culture for Detecting Neisseria gonorrhoeae in Genital and Nongenital Specimens in a Low-Prevalence Population in New Zealand

Bromhead¹,

Miller²,

Jones³

et al. 2013

J Clin Microbiol

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“…Samples were tested for Chlamydia with the Roche Cobas 4800 CT/NG PCR assay. 12 Data were analysed in Microsoft Excel. A two-tailed test of proportions was used to determine confidence intervals and P values.…”

Section: Methodsmentioning

confidence: 99%

Rectal Chlamydia in heterosexual women: more questions than answers

Ding

Challenor

2013

Int J STD AIDS

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The aim of this study was to observe the proportion of concurrent rectal Chlamydia (RCt) infection in women who have cervical Chlamydia (CCt) and to observe whether there was any correlation with receptive anal intercourse (RAI). Untreated CCt-positive women were invited to take part. Women chose either to have a physician-collected or self-taken rectal swab. Treatment was then commenced. 17 samples were physician-collected and 80 were self-collected. 75/97 (77.3%, 95% Confidence Interval [95%CI] 69.0-85.7%) were RCt positive. 25/97 (25.8%, 95%CI 17.1-34.5%) reported RAI. There was no difference in the positivity rate whether RAI was reported (80%) or not (76%) (P = 0.71); or whether swabs were physician-collected (65%) or self-taken (80%) (P = 0.17). Only one of those with RCt reported rectal symptoms. One woman had concurrent gonococcal infection. 34/97 (35%) had a history of past sexually transmitted infections. Verified contact attendance was 0.52 and 72% of verified contacts were Chlamydia positive. Reported RAI may not be helpful in guiding RCt testing. RCt infection in women may be more prevalent than previously thought. We do not know whether RCt infections are clinically significant or whether they may act as a reservoir for re-infection. RCt infections in women require further study.

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“…The Roche cobas 4800 CT/NG assay is a later-generation NAAT method, and the NG component of the assay utilizes a dual-target approach, using two assays to detect sequences within the directrepeat (DR-9) region (3). Performance data to date show excellent sensitivity and specificity for urogenital specimens (3-7), and it has been suggested that the assay does not require a second test to confirm urogenital positive results (6). Also, to our knowledge, there have been no definitive reports of the assay cross-reacting with commensal Neisseria strains (3,8); while initial testing in a study by Tabrizi et al (8) showed that the cobas 4800 NG assay cross-reacted with two commensal Neisseria strains, both were negative upon retesting using fresh cultures (8).…”

mentioning

confidence: 99%

Neisseria gonorrhoeae False-Positive Result Obtained from a Pharyngeal Swab by Using the Roche cobas 4800 CT/NG Assay in New Zealand in 2012

Upton¹,

Bromhead²,

Whiley

2013

J Clin Microbiol

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cThe Roche cobas 4800 CT/NG assay is a commonly used commercial system for screening for Neisseria gonorrhoeae infection, and previous studies have shown the method to be highly sensitive and specific for urogenital samples. We present the first confirmed clinical N. gonorrhoeae false-positive result using the cobas 4800 NG assay, obtained from testing a pharyngeal swab sample and caused by cross-reaction with a commensal Neisseria strain. N ucleic acid amplification tests (NAATs) are widely used for the detection of gonorrhea. However, the specificity of these methods can be undermined by ongoing genetic exchange between species within the Neisseria genus, leading to commensal Neisseria strains acquiring Neisseria gonorrhoeae (NG) NAAT target sequences. For these reasons, supplementary "confirmatory" testing for N. gonorrhoeae NAATs has been widely adopted (1, 2). The Roche cobas 4800 CT/NG assay is a later-generation NAAT method, and the NG component of the assay utilizes a dual-target approach, using two assays to detect sequences within the directrepeat (DR-9) region (3). Performance data to date show excellent sensitivity and specificity for urogenital specimens (3-7), and it has been suggested that the assay does not require a second test to confirm urogenital positive results (6). Also, to our knowledge, there have been no definitive reports of the assay cross-reacting with commensal Neisseria strains (3, 8); while initial testing in a study by Tabrizi et al. (8) showed that the cobas 4800 NG assay cross-reacted with two commensal Neisseria strains, both were negative upon retesting using fresh cultures (8). Herein, we report the first clinical demonstration of a Roche cobas 4800 NG falsepositive result obtained from a pharyngeal swab sample and caused by a reproducible cross-reaction with a commensal Neisseria strain.On 17 September 2012, as part of the heightened awareness program sponsored by the New Zealand AIDS Foundation, selfreferred throat and rectal swabs and a first-void urine were received from a 38-year-old male presenting to a sexual health clinic in Auckland, New Zealand. The samples were tested by PCR for N. gonorrhoeae and Chlamydia trachomatis (CT) on the Roche cobas 4800 CT/NG assay at Labtests, Auckland, New Zealand (Table 1). The three specimens were all negative for C. trachomatis DNA; the urine and rectal swabs were also negative for N. gonorrhoeae DNA. The throat swab was positive for N. gonorrhoeae DNA with a cycle threshold value of 35.7, which was confirmed upon retesting at a second laboratory (Aotea Pathology, Wellington; cobas 4800 NG assay positive with a cycle threshold value of 35.3), and the patient was treated with 500 mg intramuscular ceftriaxone. As part of an ongoing study investigating the specificity of the cobas 4800 NG assay in our population, the specimen was subsequently referred for supplementary testing by the Abbott m2000 real-time PCR (Canterbury Health Laboratories) and in-house PCR methods targeting the gonococcal porA and opa genes (Aotea Pathology, Welli...

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Screening tests forChlamydia trachomatisorNeisseria gonorrhoeaeusing the cobas 4800 PCR system do not require a second test to confirm: an audit of patients issued with equivocal results at a sexual health clinic in the Northwest of England, UK

Cited by 13 publications

References 4 publications

Comparison of the cobas 4800 CT/NG Test with Culture for Detecting Neisseria gonorrhoeae in Genital and Nongenital Specimens in a Low-Prevalence Population in New Zealand

Comparison of the cobas 4800 CT/NG Test with Culture for Detecting Neisseria gonorrhoeae in Genital and Nongenital Specimens in a Low-Prevalence Population in New Zealand

Rectal Chlamydia in heterosexual women: more questions than answers

Neisseria gonorrhoeae False-Positive Result Obtained from a Pharyngeal Swab by Using the Roche cobas 4800 CT/NG Assay in New Zealand in 2012

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