The performance of the Becton Dickinson BDProbe Tec ET System Chlamydia trachomatis and Neisseria gonorrhoeae Amplified DNA Assays (BD Biosciences, Sparks, Md.) was evaluated in a multicenter study. Specimens were collected from 2,109 men and women, with or without symptoms, attending sexually transmitted disease, family planning, and obstetrics and gynecology clinics. Both swab and urine samples were collected, and the results obtained from 4,131 specimens were compared to those from culture and the LCx nucleic acid amplification test (Abbott Industries, Abbott Park, Ill.). PCR and cytospin of the culture transport medium with chlamydia direct fluorescent antibody staining were used to adjudicate chlamydia culture-negative results. Sensitivity and specificity were calculated both with and without use of the amplification control (AC), with little apparent difference in the results. Without the AC result, sensitivity for C. trachomatis and N. gonorrhoeae were 92.8 and 96.6%, respectively, for cervical swabs and 80.5 and 84.9% for urine from women. C. trachomatis and N. gonorrhoeae sensitivities were 92.5 and 98.5%, respectively, for male urethral swabs and 93.1 and 97.9% for urine from men. This amplified DNA system for simultaneous detection of chlamydial and gonococcal infections demonstrated superior sensitivity compared to chlamydia culture and has performance characteristics comparable to those of other commercially available nucleic acid-based assays for these organisms.

The greater sensitivity of nucleic acid amplification tests (NAATs) for Chlamydia trachomatis and Neisseria gonorrhoeae permits the use of urine and other noninvasive specimens, which can increase the reach and decrease the costs of public health screening programs aimed at controlling these infections. This study evaluated the performance of the APTIMA Combo 2 assay, a multiplex assay based on the transcriptionmediated amplification reaction, for the simultaneous detection of both pathogens in endocervical swab and urine specimens from females. Combo 2 assay results were compared with patient infected status, which were available by using other commercial NAATs. Sensitivity and specificity for C. trachomatis were 94.2 and 97.6%, respectively, in swabs and 94.7 and 98.9%, respectively, in first-catch urine (FCU). Sensitivity and specificity for N. gonorrhoeae were 99.2 and 98.7%, respectively, in swabs and 91.3 and 99.3%, respectively, in FCU. The assay reliably detected both infections in coinfected patients. The Combo 2 assay can be recommended for use with endocervical swab and urine specimens from females, especially for screening tests for asymptomatic women in sexually transmitted disease surveillance programs. This Food and Drug Administration-cleared assay can be a useful tool in efforts to reduce the prevalence and incidence of C. trachomatis and N. gonorrhoeae infections in sexually active women and to prevent their costly and serious sequelae.

The infected patient standard reduces the sensitivity of the endocervical evaluation because some infected patients are positive only with FCU. The reduction in sensitivity is greater when testing for CT. Specificities improved slightly, because some unique cx positives, initially classified as false-positive were confirmed by a positive FCU result. Sensitivity of AC2 was higher than LCR, PCR, and culture. Specificity was slightly lower, but discrepant analysis (using alternate TMA targets) of apparent AC2 false-positives showed that 75% to 80% were true-positives.

Nucleic acid amplification tests (NAATs) can be used to define the infected-patient "gold standard" for the purpose of designing studies of the performance of Chlamydia trachomatis diagnostic tests. It is unclear how many test results run by different NAATs and what combinations of specimens comprise the best infectedpatient gold standard. We approached this question with data from a large study of the performance of a new NAAT. Data were available from three endocervical swabs and a urine specimen collected from each of 1,412 women and tested by three different NAATs. Results from all three assays were used equally in a rotating fashion to define the infected-patient gold standard. Multiple different infected-patient gold standards for estimating swab and urine specimen sensitivity and specificity for one NAAT method were created by varying the number and combinations of swab and urine comparator results with two different NAATs, The effect of changing the infected-patient gold standard definition was determined by constructing receiver-operator-like curves with calculated sensitivities and specificities for each test. The one-positive-of-two-results or twopositive-of-two-results (same or two different assays) infected-patient gold standard definitions produced low sensitivity and low specificity estimates, respectively. If four comparator NAAT results were used, the anythree-positive-of-four-results definition or the at-least-one-specimen-positive-by-each-of-two-comparator-assays definition appeared to provide better combinations of sensitivity and specificity estimates. The any-twopositive-out-of-three-results definition resulted in estimates that were as good as produced with the former two definitions. This analytic approach provides a means of clearly visualizing the effects of changing NAAT-based infected-patient gold standards and should be helpful in designing future studies of new C. trachomatis diagnostic tests.Determination of the infected patient "gold standard" for measuring the performance of new nucleic acid amplification tests (NAATs) for the detection of Chlamydia trachomatis in genitourinary specimens has proven difficult. Historically, culture was the gold standard for determining the performance characteristics of new diagnostic tests for this organism. Based on the analytical sensitivity of NAATs in addition to the fact that it was known that culture was not optimally sensitive, it was reasonably clear initially that these assays would be more sensitive than C. trachomatis culture. Indeed, studies showed that the use of culture alone as a reference standard resulted in significant underestimates of the specificity for NAATs as many infected patients were considered falsely negative by culture (7, 13).To address this problem, investigators applied an alternative target amplification assay to the putative false-positive results (discrepancy analysis). There was no alternative at the time, as tests with similar sensitivity were not available for use in a composite infected-patient definition a...

Screening more men with NAAT assays may provide the possibility of reducing the overall burden of chlamydia in both men and women.

SYNOPSISObjectives. To identify cases and determine risk factors for an outbreak of Escherichia coli (E. coli) O157:nonmotile (NM) infections in children attending a summer day care program in California.Methods. The authors conducted a retrospective cohort study; the cohort comprised first and second graders who attended the day care program during the last week in August 1999. Shiga toxin testing and molecular subtyping using pulsed-field gel electrophoresis were performed on isolates. Lake water, lake bottom sediment samples, and waterfowl feces from the lake environs were cultured for E. coli O157.Results. Three cases of Shiga toxin-producing E. coli O157:NM infections with matching pulsed-field gel electrophoresis patterns and four probable cases were found. Children who swallowed more than a mouthful of water had a higher attack rate than those who swallowed less than a mouthful or none at all (43% vs. 10%, relative risk = 4.43, 95% confidence interval 1.12, 17.50).Conclusions. E. coli O157:NM infections were associated with swallowing water from a freshwater lake. Potential sources of contamination include feces from humans, cattle, or deer. This outbreak illustrates the value in screening patients with diarrhea for E. coli O157, submitting isolates to public health laboratories, and using molecular techniques to identify related cases. Outbreaks associated with contaminated freshwater could be averted by prevention and early detection of contamination.

E. coli O157: NM infections were associated with swallowing water from a freshwater lake. Potential sources of contamination include feces from humans, cattle, or deer. This outbreak illustrates the value in screening patients with diarrhea for E. coli O157, submitting isolates to public health laboratories, and using molecular techniques to identify related cases. Outbreaks associated with contaminated freshwater could be averted by prevention and early detection of contamination.

Many laboratories use a commercial enzyme immunoassay (EIA) with verification testing to diagnose Chlamydia trachomatisinfections in an effort to contain costs. This study was designed to compare the performance and cost-effectiveness of direct fluorescent-antibody assay (DFA), commercial PCR, and ligase chain reaction (LCR) for the verification of EIA results. Cervical specimens were screened by EIA. DFA, PCR, and LCR were compared as verification tests for EIA-reactive specimens and negative greyzone (NGZ) specimens at 50% below the cutoff value. These samples were also tested by in-house PCR, which was used in the analysis of verification results. A total of 477 (7%) of 6,571 samples were reactive or within the NGZ. EIA results with verification by DFA testing (EIA/DFA results) agreed with 93% of the true results compared with 97% for EIA/PCR results for one set of 242 samples; there was 97% agreement with true results for EIA/DFA results versus 95% for EIA/LCR results for another set of 235 samples. Ten samples were false positive by LCR. Time and costs were equivalent for EIA with the DFA, PCR, or LCR as the verification test but were two- to threefold greater for PCR or LCR alone than for EIA with verification. Since it is important to balance cost containment with public health objectives, DFA, PCR, and LCR as EIA verification tests for cervical samples offer acceptable sensitivities and specificities at reasonable cost for low- to moderate-risk populations and therefore can be extended to a broader spectrum of at-risk populations.