Feasibility and cost-benefit of implementing pooled screening for HCVAg in small blood bank settings.

To examine the accuracy, feasibility and benefits of screening for hepatitis C virus core antigen (HCVAg) using enzyme-linked immunosorbent assay (ELISA) test in pools. Many countries cannot afford to test blood donations for hepatitis C using molecular methods. Screening individual units using the ELISA HCVAg test is an acceptable, yet still expensive, alternative, especially for small blood bank settings. This study evaluated the option of screening for HCVAg in pools. The sensitivity (Se) and specificity (Sp) of HCVAg in pools of three and six antibody-negative samples were estimated and compared with polymerase chain reaction (PCR). The feasibility and cost-benefit of the assay was assessed on 960 routine samples collected at a hospital blood bank in Gaza. Based on results for 50 PCR-positive pools and 50 and 110 PCR-negative pools of three and six, the Se of testing in pools of three and six samples is 80-82% [95% confidence interval (CI): 66.3-91.4] and Sp >or=98% (95% CI: 89.4-100.0) compared with PCR. The incidence of antigen in donors in Gaza was 0.1% (95% CI: 0-0.56). Cost analyses suggested significant benefits from implementing screening blood donations for HCVAg when the incidence rate is >4.2/10,000, leading to reduction in the expenditures needed to treat patients infected with HCV. The risk of transfusion-transmitted hepatitis C in resource-deprived developing countries can be efficiently reduced by additional screening of antibody-negative blood donations for HCVAg in pools of six.

Primary osteoarthritis of hip, knee, and hand in relation to occupational exposure.

AIM: To identify occupations with excess prevalence of osteoarthritis of the knee, hip, and hand in a nationwide survey and to compare occupations with and without excess prevalence with regard to biomechanical stresses and severity of osteoarthritis. METHODS: Patients presenting with osteoarthritis of the knee, hip, or hand were recruited throughout France by their treating physician who collected information on history, including age at onset, occupation, and occupational stresses to joints. Severity was assessed using joint specific functional status questionnaires: Lequesne for the hip and knee and Dreiser for the hand. The distribution of osteoarthritis patients by occupation was compared with the distribution of occupations in all workers in France to obtain prevalence rate ratios. RESULTS: Occupations with the greatest prevalence rate ratio were female cleaners (6.2; 95% CI 4.6 to 8.0), women in the clothing industry (5.0; 95% CI 3.9 to 6.3), male masons and other construction workers (2.9; 95% CI 2.6 to 3.3), and agriculture male and female workers (2.8; 95% CI 2.5 to 3.2). A twofold greater prevalence rate was observed within certain occupations between self-employed and salaried workers. Early onset of osteoarthritis was seen in the more heavy labour jobs with almost 40% of patients reporting their first symptoms before the age of 50. CONCLUSION: The early onset and severity of osteoarthritis in certain occupations warrants an urgent need for occupation specific studies for the development and evaluation of preventive strategies in this leading cause of disability in Western countries.

Health and safety implications of exposure to electromagnetic fields in the frequency range 300 Hz to 10 MHz.

An international seminar on health effects of exposure to electromagnetic fields (EMF) in the frequency range from 300 Hz to 10 MHz (referred to as the Intermediate Frequency (IF) range) was held in Maastricht, Netherlands, on 7-8 June 1999. The seminar, organized under the International EMF Project, was sponsored jointly by the World Health Organization (WHO), the International Commission on Non-Ionizing Radiation Protection (ICNIRP), and the Government of the Netherlands. This report does not attempt to summarize all of the material presented at the conference, but focuses on sources of exposure, biophysical and dosimetric considerations pertinent to extrapolating biological data from other frequency ranges to IF and identifies potential health concerns and needs for developing exposure guidelines. This paper is based on presentations at the conference and reports of working groups consisting of the speakers and other experts. It concludes with recommendations for further research aimed at improving health risk assessments in this frequency range.

Cost and quality under managed care: irreconcilable differences?

Managed care companies contend there is still waste in the healthcare system that should be eliminated. Healthcare providers argue that further cuts will reduce quality. Which side is right? In order to answer this question it is necessary to determine the threshold implicit in the corollary question: How far can we go in reducing healthcare expense without diminishing quality? A new variability based methodology is proposed that has the potential to determine the threshold at which cost reduction will negatively impact quality. Illustrations of its specific application are provided.

Whose blood is safer? The effect of the stage of the epidemic on screening for HIV.

BACKGROUND: With improvements in HIV antibody test (ELISA) performance, the window of time between infection and seroconversion becomes a major source of error in HIV screening. The authors examined its impact on the false-reassurance rate (FRR). METHODS: Test sensitivity was modeled as the product of two factors: the inherent sensitivity (sensitivity when antibody is present) and the probability that antibody is present in infected blood. A model of HIV and AIDS incidence was used to derive an estimate of the probability of remaining in the seronegative window (pw) among those who are infected. With plausible assumptions, this probability approaches 0.03. The FRR was then estimated as a function of the probability of remaining in the seronegative window, the prevalence of HIV, and the inherent sensitivity of the ELISA test were estimated. RESULTS: The FRRs for two blood donor groups, one with an HIV prevalence of 0.004 and a typical probability of remaining in the seronegative window (pw = 0.03) and the other with a higher prevalence of 0.017 but fewer donors in the window (pw = 0.003), are equal (140 per million donors) if the blood is negative on a single ELISA test. After two negative tests or a single test that can detect antibody more reliably, however, the FRR is much higher in the group with the higher pw (= 120 per million compared with 50 per million), because the greater numbers of donors in the window more than offsets the lower prevalence. CONCLUSION: With improvements in inherent sensitivity of ELISA by virtue of technical progress or retesting, the prevalence of HIV infection may no longer play the critical role in degrading the results of blood screening. As inherent test performance improves, tests are increasingly likely to miss infected blood because of the seronegative-window error rather than because of measurement error. Window error plays a proportionally greater role during the early stages of HIV dissemination in a population where the incidence of new HIV infection is high relative to the incidence of AIDS. These findings may explain, in part, the recent observation that cases of transfusion of contaminated blood often take place in areas where AIDS epidemics have started recently. They also suggest that the traditional strategy of soliciting blood donors from low-prevalence populations may not always be optimal, unless such populations are truly low-risk.

Studies of AIDS and HIV surveillance. Screening tests: can we get more by doing less?

Estimating the prevalence of the human immunodeficiency virus (HIV) in a group is challenging; this is especially so when the prevalence is small. One reason is that the presence of measurement errors resulting from the limited precision of tests makes estimation, using traditional methods, impossible in some screening situations. Measurement error is real, ignoring it leads to severe bias, and inference about the prevalence becomes unsatisfactory. Indeed, in a low prevalence situation the expected number of false positives is very high, often even higher than the number of true positives. The second reason is that in the low prevalence areas the large sample is needed in order to obtain non-zero estimate. This is usually a very costly, and often unrealistic, solution. This paper considers the advantages and disadvantages of pooled testing as an alternative solution to this problem. We show that by pooling sera samples we not only achieve a cost saving but also, which is counterintuitive, an increase in the estimation accuracy. We also discuss the statistical issues associated with the resulting estimator.

Issues in human immunodeficiency virus (HIV) screening programs.

Unlike test sensitivity and specificity, the false positive and negative predictive values (probabilities of mislabeling an individual being tested) depend heavily on the prevalence of the infection of the human immunodeficiency virus (HIV) as well as the quality of the kit. A consequence of this dependence is that the false positive predictive value can reach a high magnitude such as 0.9; that is, 90% of the positive tests are false. This raises many important issues pertaining to the current practice of HIV screening such as to how to control these misclassification errors, how to interpret test results, and how to estimate prevalence using test results. These issues are examined in detail here by considering the factors that dictate the quality of a screening program. Some real data examples are used to illustrate the importance of this consideration in designing programs to achieve the desired goals. The rationale behind the common two-step sequential protocol in HIV screening is examined to point out its limitations under practical situations. Finally, the use of entropy in evaluating the informativeness of a screening program is discussed.

[Intracranial oncogenic aneurysm]. / Vnutricherepnaia onkogennaia anevrizma.

The paper deals with a death from cerebrosubarachnoidal hemorrhage in a 22-year-old male. Autopsy revealed fusiform aneurysm at the junction of right posterior connective and cerebral arteries whose wall was histologically examined. The examination indicated that the wall was invaded by tumor cells from the endothelium, the internal elastic membrane and vascular muscle layer being destructed. The primary cause of the tumor was a testis removed 40 days before the death and diagnosed as having chorionepithelioma.