A combined testing protocol approach for mutagenicity testing

The antischistosomal agent, hycanthone methanesulfonate (HMS), was employed to illustrate the utility of carrying out several mutagenicity tests in a single concurrent animal experiment. Several commonly used procedures that were successfully integrated into a multiple testing protocol included (1) metaphase analysis in bone marrow, (2) micronucleus test in bone marrow, (3) analysis of the urine for mutagenic constituents, and (4) the host-mediated assay using Salmonella typhimurium. In addition to these animal studies, in vitro mutagenicity testing with and without activation was carried out using S. typhimurium.HMS produced positive, dose—response effects in in vitro tests, metaphase analysis, micronucleus test, and urine analysis, but not in the host-mediated assay. The results of these integrated techniques suggest that such a protocol may be a benefit to those concerned with mutagenicity testing of chemicals.     

A combined testing protocol approach for mutagenicity testing.

The antischistosomal agent, hycanthone methanesulfonate (HMS), was employed to illustrate the utility of carrying out several mutagenicity tests in a single concurrent animal experiment. Several commonly used procedures that were successfully integrated into a multiple testing protocol included (1) metaphase analysis in bone marrow, (2) micronucleus test in bone marrow, (3) analysis of the urine for mutagenic constituents, and (4) the host-mediated assay using Salmonella typhimurium. In addition to these animal studies, in vitro mutagenicity testing with and without activation was carried out using S. typhimurium. HMS produced positive, dose--response effects in in vitro tests, metaphase analysis, micronucleus test, and urine analysis, but not in the host-mediated assay. The results of these integrated techniques suggest that such a protocol may be a benefit to those concerned with mutagenicity testing of chemicals.     

Combined Pap smear, cervicography and HPV DNA testing in the detection of cervical intraepithelial neoplasia and cancer

OBJECTIVE: The sensitivity of the Pap smear (PAP) continues to be the subject of debate. During the past several years, cervicography (CER) and HPV DNA testing have been suggested as optional tools in the screening of cervical cancer precursors. STUDY DESIGN: The performance characteristics of PAP, CER and HPV DNA testing (hybrid capture test [HCT]) in all potential combinations were evaluated in a series of 1,030 women (aged 16-70, median, 33), subjected to colposcopy (COLPO) as the reference tool. RESULTS: Of the 992 evaluable cases, 402/992 (41%) had positive COLPO (i.e., an abnormal transformation zone). Of them, 298 women underwent directed punch biopsy, while of the COLPO negative patients, 18/93 positive by at least one of the three tests had endocervical curettage. Of the 402 COLPO positive women, 146 (36%) remained negative on all tests, whereas 256 (64%) had at least one positive test. There were 84 cervical intraepithelial neoplasia (CIN) 2 and 3 lesions and 6 invasive carcinomas. Of the former, 10 were detected by PAP alone, 4 by CER alone and 3 by HCT alone. Three of the 6 carcinomas were HCT negative. The predictive value (PPV) of a positive test was 45% for PAP, 51% for CER and 48% for HCT. The combinations of PAP with CER (for PAP negative cases) and PAP with HCT were more sensitive for CIN 2 and 3 (95% and 94%, respectively) as compared with PAP alone but were associated with a significant decrease in specificity (44% and 46% vs. 57%, respectively). However, both combinations retained a PPV (43%) similar to that of PAP alone (45%). CONCLUSION: The potential combinations of PAP with CER and with HCT were more sensitive in detecting CIN 2 and 3 as compared with PAP alone and retained a PPV similar to that of PAP.     

Effectiveness of VIA, Pap, and HPV DNA testing in a cervical cancer screening program in a peri-urban community in Andhra Pradesh, India

Background

While many studies have compared the efficacy of Pap cytology, visual inspection with acetic acid (VIA) and human papillomavirus (HPV) DNA assays for the detection cervical intraepithelial neoplasia and cancer, few have evaluated the program effectiveness.

Methods and Findings

A population-based sample of 5603 women from Medchal Mandal in Andhra Pradesh, India were invited to participate in a study comparing Pap cytology, VIA, and HPV DNA screening for the detection of CIN3+. Participation in primary screening and all subsequent follow-up visits was rigorously tracked. A 20% random sample of all women screened, in addition to all women with a positive screening test result underwent colposcopy with directed biopsy for final diagnosis. Sensitivity, specificity, positive and negative predictive values were adjusted for verification bias. HPV testing had a higher sensitivity (100%) and specificity (90.6%) compared to Pap cytology (sensitivity  =  78.2%; specificity = 86.0%) and VIA (sensitivity = 31.6%; specificity = 87.5%). Since 58% of the sample refused involvement and another 28% refused colposcopy or biopsy, we estimated that potentially 87.6% of the total underlying cases of CIN3 and cancer may have been missed due to program failures.

Conclusions

We conclude that despite our use of available resources, infrastructure, and guidelines for cervical cancer screening implementation in resource limited areas, community participation and non-compliance remain the major obstacles to successful reduction in cervical cancer mortality in this Indian population. HPV DNA testing was both more sensitive and specific than Pap cytology and VIA. The use of a less invasive and more user-friendly primary screening strategy (such as self-collected swabs for HPV DNA testing) may be required to achieve the coverage necessary for effective reduction in cervical cancer mortality.     

Comparative analysis of a liquid-based Pap test and concurrent HPV DNA assay of residual samples. A study of 608 cases

OBJECTIVE: To retrospectively study the HPV DNA assay of residual samples from the ThinPrep Pap Test (Cytyc Corporation, Boxborough, Massachusetts, U.S.A.) PreserveCyt (Cytyc) vial as a quality improvement (QI) indicator for management of patients with abnormal cervical cytology. STUDY DESIGN: Six hundred eight residual sample vials of liquid-based Pap-Test specimens were selected for the study based on Pap-test results from October 1998 to March 2001. The specimen vials were forwarded to the reference laboratory (American Medical Laboratories, Chantilly, Virginia, U.S.A.) for HPV DNA assay using the Hybrid Capture System method (Digene Corporation, Gaithersburg, Maryland, U.S.A.). At the time of HPV DNA assay, the residual samples were between 8 days to 10 months old, and each vial contained 4 mL. Of the 608 study cases, 76 were WNL, 115 contained BCC, 172 contained ASCUS, 179 were LSIL and 66 were HSIL. In this study, the 191 WNL and BCC cases were designated as the disease-free control group. The HPV DNA typing results were reported as low-risk, high/intermediate-risk or HPV DNA "not detected" HPV types. The HPV DNA testing results were compared to the Pap-Test diagnoses and statistical analysis performed. RESULTS: The following information reflects the percentage of HPV DNA-positive cases based on the Pap-Test diagnoses: 16.2% in WNL and BCC, 51.1% in ASCUS, 94.4% in LSIL and 98.4% in HSIL. Sensitivity (95.5%), specificity (83.7%), false negative value (4.4%), false positive value (16.2%) and predictive value of a positive (88.3%) and negative (93.5%) Pap-Test were calculated on the basis of HPV DNA testing results for 436 cases that were diagnosed as either SIL or negative (WNL and BCC). ASCUS (172) Pap-Test cases were considered borderline--disease positive and excluded from statistical analysis. CONCLUSION: The HPV DNA assay of residual samples from ThinPrep Pap-Test liquid-based specimens is an objective adjunct to the gynecologic cytology QI protocol and is the gold standard reference test for triaging women with equivocal cytologic diagnoses. The great value of HPV DNA testing is its high sensitivity (95.5%), specificity (83.7%) and negative predictive value (93.5%). HPV DNA testing results can be used as a tool to better determine the need for referrals for colposcopic biopsy, especially for patients with an ASCUS diagnosis. The residual Pap-Test specimens are stable and reproducible for HPV DNA typing. A working flow chart for our gynecologic cytology QI program was produced from the Pap-Test and HPV DNA assay results. This offer presents the added benefit of minimizing the problem of sample variation. The prevalence of HPV infection was 16.2% in this study.     

The diagnostic sensitivity of dengue rapid test assays is significantly enhanced by using a combined antigen and antibody testing approach

Background

Serological tests for IgM and IgG are routinely used in clinical laboratories for the rapid diagnosis of dengue and can differentiate between primary and secondary infections. Dengue virus non-structural protein 1 (NS1) has been identified as an early marker for acute dengue, and is typically present between days 1–9 post-onset of illness but following seroconversion it can be difficult to detect in serum.

Aims

To evaluate the performance of a newly developed Panbio® Dengue Early Rapid test for NS1 and determine if it can improve diagnostic sensitivity when used in combination with a commercial IgM/IgG rapid test.

Methodology

The clinical performance of the Dengue Early Rapid was evaluated in a retrospective study in Vietnam with 198 acute laboratory-confirmed positive and 100 negative samples. The performance of the Dengue Early Rapid in combination with the IgM/IgG Rapid test was also evaluated in Malaysia with 263 laboratory-confirmed positive and 30 negative samples.

Key Results

In Vietnam the sensitivity and specificity of the test was 69.2% (95% CI: 62.8% to 75.6%) and 96% (95% CI: 92.2% to 99.8) respectively. In Malaysia the performance was similar with 68.9% sensitivity (95% CI: 61.8% to 76.1%) and 96.7% specificity (95% CI: 82.8% to 99.9%) compared to RT-PCR. Importantly, when the Dengue Early Rapid test was used in combination with the IgM/IgG test the sensitivity increased to 93.0%. When the two tests were compared at each day post-onset of illness there was clear differentiation between the antigen and antibody markers.

Conclusions

This study highlights that using dengue NS1 antigen detection in combination with anti-glycoprotein E IgM and IgG serology can significantly increase the sensitivity of acute dengue diagnosis and extends the possible window of detection to include very early acute samples and enhances the clinical utility of rapid immunochromatographic testing for dengue.     

A test of a corollary of Allen's rule suggests a role for population density

A body of research by Russell Greenberg, Glenn Tattersall and their colleagues has proposed a corollary of Allen's Rule: that in freshwater‐limited environments, bill surface area increases with temperature. Increases in both population density and sexual dimorphism, however, could also explain increases in bill surface area. After controlling for the effects of a hybrid zone, we tested whether temperature or population density in the saltmarsh sparrow Ammospiza caudacuta, a sexually monomorphic estuarine specialist, explained greater variance in bill surface area. This allowed us to examine multiple potential selective mechanisms underlying the Greenberg–Tattersall corollary. We found that saltmarsh sparrows follow the general pattern of the corollary (larger bills in warmer summer climates) but only after controlling for population density. The relationship between bill surface area and temperature varied inversely with population density. We discuss the relative abilities of sexual selection and ecological competition to explain these results.     

HPV testing for cervical cancer screening in Croatia

Opportunistic screening based on the Pap smear has been undertaken in Croatia since 1953. However, cervical cancer remains an important health problem in Croatia when compared to European countries with organised screening programmes. In Croatia, in addition to screening based on well established cytology, Human papillomavirus (HPV) testing is widely used as secondary test as a triage to borderline cytology and as a follow-up after treatment of severe cervical lesions. Many different approaches for HPV testing arose in Croatia over the last decade depending on the needs of each medical institution involved. Presently, there is an urgent need for better networking between the laboratories, the implementation of quality assessment and the adaptation of a uniform system of referring to and reporting of HPV testing. In conclusion, the best possible organisation for HPV testing would be essential for implementation of HPV testing as primary screening test in Croatia, an thus ultimately and hopefully, the more successful cervical cancer control.     

A unified approach for quantifying, testing and correcting population stratification in case-control association studies

The HapMap project has given case-control association studies a unique opportunity to uncover the genetic basis of complex diseases. However, persistent issues in such studies remain the proper quantification of, testing for, and correction for population stratification (PS). In this paper, we present the first unified paradigm that addresses all three fundamental issues within one statistical framework. Our unified approach makes use of an omnibus quantity (delta), which can be estimated in a case-control study from suitable null loci. We show how this estimated value can be used to quantify PS, to statistically test for PS, and to correct for PS, all in the context of case-control studies. Moreover, we provide guidelines for interpreting values of delta in association studies (e.g., at alpha = 0.05, a delta of size 0.416 is small, a delta of size 0.653 is medium, and a delta of size 1.115 is large). A novel feature of our testing procedure is its ability to test for either strictly any PS or only 'practically important' PS. We also performed simulations to compare our correction procedure with Genomic Control (GC). Our results show that, unlike GC, it maintains good Type I error rates and power across all levels of PS.     

Speciation in parasites: a population genetics approach

Parasite speciation and host-parasite coevolution should be studied at both macroevolutionary and microevolutionary levels. Studies on a macroevolutionary scale provide an essential framework for understanding the origins of parasite lineages and the patterns of diversification. However, because coevolutionary interactions can be highly divergent across time and space, it is important to quantify and compare the phylogeographic variation in both the host and the parasite throughout their geographical range. Furthermore, to evaluate demographic parameters that are relevant to population genetics structure, such as effective population size and parasite transmission, parasite populations must be studied using neutral genetic markers. Previous emphasis on larger-scale studies means that the connection between microevolutionary and macroevolutionary events is poorly explored. In this article, we focus on the spatial fragmentation of parasites and the population genetics processes behind their diversification in an effort to bridge the micro- and macro-scales.     

FINDRISK questionnaire combined with HbA1c testing as a potential screening strategy for undiagnosed diabetes in a healthy population

Despite the efforts to control the epidemic of diabetes the total number of people living with diabetes is still steadily rising. In order to detect people at risk, cost-effective, convenient, and sensitive screening tools to assess the diabetes risk and to detect undiagnosed type 2 diabetes need to be developed and implemented in the primary care setting. To evaluate the combination of the well established FINDRISK questionnaire and HbA1c testing as a potential screening strategy the data obtained from 671 blood donors were analyzed for a potential correlation with the results of an oral glucose tolerance test. Based on the oral glucose tolerance test, 65 blood donors (9.7%) were newly diagnosed with diabetes, 336 (50.1%) with prediabetes, and 270 (40.2%) had a normal test result. Of the 401 blood donors diagnosed with prediabetes or diabetes 322 (80.3%) had a HbA1c between 5.7% and 6.4% and 27 (6.7%) with a HbA1c of 6.5% or greater. The majority of the blood donors newly diagnosed with diabetes or prediabetes (n=327) had a FINDRISK result of 12 points or higher. ROC analyses confirmed that the optimal cut off levels were for FINDRISK ≥ 12 points and for HbA1c ≥ 5.9%. Thus, a 3-step screening strategy applying the FINDRISK questionnaire followed by HbA1c testing and performing an oral glucose tolerance test on selected individuals could be a cost-saving approach for screening large populations and identifying people at risk for diabetes or undiagnosed diabetes.