Performance Validation of the Microbiologique MicrofilmTM Test System for AOAC Research Institute Performance Tested MethodSMCertification.

The Microfilm™ Test System is intended for quantitative microbiology and consists of three types of Microfilms for aerobic plate count (Microfilm APC), total coliform and Escherichia coli count (Microfilm TCEc), and yeast and mold count (Microfilm YMC). This study evaluated the performance of the Microfilm Test System against International Organization for Standardization (ISO) methods on 20 food matrixes and 2 environmental surfaces. Ruggedness, robustness, and stability were also determined, while inclusivity and exclusivity studies were performed on Microfilm TCEc and YMC. An independent laboratory evaluated the performance on four food matrixes and one environmental surface. No significant differences and high correlation coefficients were observed between the Microfilm Test System and the corresponding ISO methods (ISO 4833-1:2013 for APC, ISO 4832:2006 for total coliform count, ISO 16649-2: 2001 for E. coli, and ISO 21527 Part 1 and Part 2 for YMC) in spiked food matrixes and environmental samples. These results were corroborated by the independent laboratory. Inclusivity and exclusivity studies for Microfilm TCEc showed expected results for all the E. coli strains tested (blue-violet or violet color), while the related coliforms showed the expected blue-green colonies on the Microfilm. Similarly, all 100 fungal strains tested showed typical growth on Microfilm YMC. Exclusivity testing on Microfilm TCEc and YMC showed no growth of nontarget organisms. Robustness and ruggedness studies showed no significant differences in mean difference counts at varying incubation temperatures and times. Stability studies on three lots of the Microfilm Test System showed that it is stable at 2-25°C for 12 months and at 45°C for 6 weeks.

Performance evaluation of a new rapid urine test for chlamydia in men: prospective cohort study.

OBJECTIVE: To evaluate the performance of a rapid test for chlamydia with first void male urine samples as a potential tool for diagnosis and screening of chlamydial infection in men. DESIGN: Evaluation of test performance in prospective cohort study. Settings A young people's sexual health centre (site 1) and a genitourinary medicine clinic (site 2) in the United Kingdom. PARTICIPANTS: 1211 men aged 16-73 attending either of the two sites. MAIN OUTCOME MEASURES: Sensitivity, specificity, positive predictive value, and negative predictive value of the Chlamydia Rapid Test versus polymerase chain reaction assay. Relation between the visual signal of the Chlamydia Rapid Test and organism load. RESULTS: Detection rates for Chlamydia trachomatis infection with polymerase chain reaction were 4.4% (20/454) at site 1 and 11.9% (90/757) at site 2. Compared with polymerase chain reaction assay, the resolved sensitivity, specificity, positive predictive value, and negative predictive value of the Chlamydia Rapid Test was 82.6% (90/109), 98.5% (1085/1102), 84.1% (90/107), and 98.3% (1085/1104), respectively. The organism load in first void urine samples that were positive for chlamydia ranged from 7.28x10(2) to 6.93x10(6) plasmids/ml and correlated significantly with the visual signal of the Chlamydia Rapid Test (r=0.7897, P<0.001). CONCLUSIONS: The performance of the new Chlamydia Rapid Test with first void male urine samples indicates that it would be an effective diagnostic tool for chlamydial infection in men. The availability of test results within an hour allows for immediate treatment and contact tracing, potentially reducing the risks of persistent infection and onward transmission. The test could also provide a simple and reliable alternative to nucleic acid amplification assays for testing of male urine in chlamydial screening programmes in high prevalence settings.

Evaluation of a new hepatitis B virus surface antigen rapid test with improved sensitivity.

A new rapid immunochromatographic assay based on the signal amplification system (SAS) has been developed by Diagnostics for the Real World (Europe) Ltd. for the detection of hepatitis B virus surface antigen (HBsAg) in plasma or serum specimens. The SAS format features enhanced sensitivity as a result of an increased binding valence of the detector molecules. We have now evaluated the performance of the new HBsAg rapid test (DRW-HBsAg) in comparison with a well-established commercial rapid test (Determine HBsAg; previously from Abbott Laboratories; now from Inverness Medical Innovations) and with a CE-marked enzyme immunoassay (EIA) (Hepanostika HBsAg Ultra; BioMérieux) as the gold standard. Testing of serially diluted in-house HBsAg-positive samples, the World Health Organization standard, and sensitivity and reference panels yielded an analytical sensitivity for the DRW test of 0.2 to 0.8 IU/ml across HBsAg serotypes. Evaluation with eight commercially available seroconversion panels showed that the DRW-HBsAg test detected HBsAg an average of 6.1 days (range, 3 to 8 days) earlier than the Determine assay (P = 0.0078). Test sensitivity was also examined with two low-titer HBsAg EIA-positive panels in Beijing, China. Whereas 100% of these samples were detected by the DRW-HBsAg test, only 15.0% (P < 0.0001) and 87.3% (P < 0.0001), respectively, were detected by the Determine HBsAg test. The performance of the DRW-HBsAg test was further evaluated with samples determined to be HBsAg positive or negative by the EIA in Conakry, Guinea, and Beijing, China. No significant difference in sensitivity between the DRW and Determine tests was apparent with the HBsAg EIA-reactive samples from Guinea (96.7% versus 94.4%, respectively) or China (99.46 versus 98.92%, respectively). The specificity of the Determine HBsAg test was slightly higher than that of DRW-HBsAg test (100 versus 99.2%, respectively) with samples from EIA-negative blood donors in China. In conclusion, the new DRW HBsAg rapid test is more sensitive than the Determine HBsAg test and is suitable for diagnostic and blood screening in resource-limited settings.

Optimal method of collection of first-void urine for diagnosis of Chlamydia trachomatis infection in men.

First-void urine (FVU) is the preferred specimen for the diagnosis of urogenital Chlamydia trachomatis infection in men. We have developed FirstBurst, a urine collection device that collects the first 4 to 5 ml of FVU and yields a specimen with a sixfold higher C. trachomatis organism load than the regular urine cup by quantitative PCR (32,533 versus 5,271 plasmids/ml; P < 0.0001). Consequently, the use of FirstBurst to collect a urine sample improved the sensitivity of a rapid test for Chlamydia over testing of samples collected with a urine cup (82 versus 47% sensitivity using PCR as a reference; P < 0.0015).

Prevalence of Chlamydia trachomatis infection among low- and high-risk Filipino women and performance of Chlamydia rapid tests in resource-limited settings.

The prevalence of urogenital Chlamydia trachomatis infection was determined with a PCR-based test of women from low- and high-risk populations in Iloilo City, Philippines, between August 2002 and March 2006. Two rapid tests for C. trachomatis, Clearview Chlamydia MF and the Chlamydia Rapid Test (CRT), were also evaluated in these resource-limited settings. Specimens were obtained from female sex workers (FSWs; n = 1,484) attending a social hygiene clinic (SHC) and from women (n = 838) attending an obstetrics-gynecology (OB-GYN) clinic. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the rapid tests were determined, with PCR as the gold standard. The PCR positivity rate for SHC participants (72% asymptomatic) ranged from 17.9 to 32.0% during the study period. Compared with those of PCR, the sensitivities and specificities of the Clearview test were 53.5 and 99.1%, respectively, with endocervical swab specimens (CS; n = 822) from the FSWs and 31.1 and 95.2%, respectively, with vaginal swab specimens (VS; n = 333) from these women. The sensitivity, specificity, PPV, and NPV of the CRT with VS from the FSWs were 71.0, 99.0, 97.1, and 87.9%, respectively. At the OB-GYN site, the PCR positivity rate with VS was 6.3%. The sensitivity, specificity, PPV, and NPV of the CRT with these specimens were 86.8, 99.6, 93.9, and 99.1%, respectively. The performance of the Clearview test at the SHC was thus markedly lower with VS than with CS, whereas the CRT performed well with VS from both populations.

Chlamydia trachomatis load at matched anatomic sites: implications for screening strategies.

Urethral and endocervical swabs and self-collected vaginal swabs (SCVSs) and urine specimens are all used as samples for diagnosis of urogenital infection with Chlamydia trachomatis. We have now determined chlamydial organism load in matched specimens from different anatomic sites and examined its relation to clinical signs and symptoms in men and women. Organism load was measured with assays based on the ligase chain reaction or real-time PCR analysis. The mean organism loads in 58 infected men were 1,200 and 821 elementary bodies (EBs) per 100 microl of sample for first-void urine (FVU) and urethral swabs, respectively (P>0.05). Organism load in FVU samples or urethral swabs was positively associated with symptoms (P<0.01) and clinical signs (P<0.01) in men. The mean organism loads in 73 infected women were 2,231, 773, 162, and 47 EBs/100 microl for endocervical swabs, SCVSs, urethral swabs, and FVU samples, respectively (P<0.001 for each comparison). Only the presence of multiple symptoms or clinical signs was associated with organism load in women. These results show that FVU is a suitable noninvasive sample type for men, given the fact that its chlamydial load did not differ significantly from that of urethral swabs. Given their higher organism load compared with FVU, SCVSs are the preferred noninvasive sample type for women.