Pooling urine samples for ligase chain reaction screening for genital Chlamydia trachomatis infection in asymptomatic women

Division of Disease Control, International Health, School of Hygiene and Public Health, The Johns Hopkins University, Baltimore, Maryland 21205, USA.
Journal of Clinical Microbiology (Impact Factor: 3.99). 03/1998; 36(2):481-5.
Source: PubMed


The accuracy of pooling urine samples for the detection of genital Chlamydia trachomatis infection by ligase chain reaction (LCR) was examined. A model was also developed to determine the number of samples to be pooled for optimal cost savings at various population prevalences. Estimated costs included technician time, laboratory consumables, and assay costs of testing pooled samples and retesting individual specimens from presumptive positive pools. Estimation of population prevalence based on the pooled LCR results was also applied. After individual urine specimens were processed, 568 specimens were pooled by 4 into 142 pools and another 520 specimens were pooled by 10 into 52 pools. For comparison, all 1,088 urine specimens were tested individually. The sample-to-cut-off ratio was lowered from 1.0 to 0.2 for pooled samples, after a pilot study which tested 148 samples pooled by 4 was conducted. The pooling algorithm was 100% (48 of 48) sensitive when samples were pooled by 4 and 98.4% (61 of 62) sensitive when samples were pooled by 10. Although 2.0% (2 of 99) of the negative pools of 4 and 7.1% (1 of 14) of the negative pools of 10 tested presumptive positive, all samples in these presumptive-positive pools were negative when retested individually, making the pooling algorithm 100% specific. In a population with 8% genital C. trachomatis prevalence, pooling by four would reduce costs by 39%. The model demonstrated that with a lower prevalence of 2%, pooling eight samples would reduce costs by 59%. Pooling urine samples for detection of C. trachomatis by LCR is sensitive, specific, and cost saving compared to testing individual samples.

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Available from: Charlotte Gaydos, Aug 30, 2014
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    • "Cost savings for these ocular samples would be seen by using 25 assay cartridges for pools and 28 cartridges for deconstructed tests for a total of 53, instead of 102 cartridges; for vaginal samples, 25 cartridges for pools and extra 56 cartridges for individual tests for a total of 81 instead of 100 individual tests. Cost savings depends on the prevalence of infection in the population being tested; as prevalence decreases, pool size can increase, resulting in higher cost savings (Diamant et al., 2001; Kacena et al., 1998; Peeling et al., 1998). In a previous study comparing pooling of ocular swabs for the detection of CT on 2 NAAT assays, an overall cost savings of 62.2% was observed, a cost-savings analysis for the GeneXpert would also be needed to determine more accurate cost savings (Dize et al., 2013). "
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    ABSTRACT: Ocular swabs from Tanzania were tested for Chlamydia trachomatis (CT), and self-collected vaginal swabs collected through a home collection program,, were tested for Neisseria gonorrhoeae (NG) and CT to evaluate Cepheid GeneXpert for the use of pooling multiple specimens before testing. GeneXpert shows to be a promising test for pooling.
    Full-text · Article · Nov 2014 · Diagnostic Microbiology and Infectious Disease
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    • "It is currently unknown how much is spent on molecular testing annually for analyzing ocular swabs for CT. However, it has been previously shown, total assay cost per specimen has been reduced by 39% (female genital specimens) and 53.3% (cervical specimens) when testing pools of 4 and 5, respectively, for CT and can result in savings of test kits alone by up to 57% (Kacena et al., 1998; Shipitsyna et al., 2007; Peeling et al., 1998). Cost effectiveness depends on infection prevalence of the population being tested and as prevalence decreases pool size increases so cost-savings will also increase (Diamant et al., 2001; Peeling et al., 1998). "
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    ABSTRACT: Ocular swabs collected in Tanzania were evaluated by Amplicor CT PCR and Aptima Combo2 assays for the detection of Chlamydia trachomatis to determine if pooling could be used to reduce the cost of detection. Pooling would be an accurate method and has thus far resulted in a cost-savings of 62.2%.
    Full-text · Article · Sep 2013 · Diagnostic microbiology and infectious disease
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    • "It is assumed that γ 1 and γ 2 are constants close to 1 and do not depend on c ij , a reasonable assumption with modern diagnostic assays based on nucleic acid technology (NAT). For a number of chlamydia studies, NATs have been shown to have high sensitivity and specificity for pools of up to size 10 when pooling urine or cervical swabs (see, e.g., Kacena et al., 1998b). Similar results have been observed in gonorrhea studies (Kacena et al., 1998a). "
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    ABSTRACT: Group testing, where subjects are tested in pools rather than individually, has a long history of successful application in infectious disease screening. In this article, we develop group testing regression models to include covariate effects that are best regarded as random. We present approaches to fit mixed effects models using maximum likelihood, investigate likelihood ratio and score tests for variance components, and evaluate small sample performance using simulation. We illustrate our methods using chlamydia and gonorrhea data collected by the state of Nebraska as part of the Infertility Prevention Project.
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