Yea-Yin Yen

Breast-feeding and maternal smoking in the etiology of Crohn's disease and ulcerative colitis in childhood

Medical records concerning pediatric or adolescent patients first diagnosed with Crohns disease or ulcerative colitis in two New York hospitals during a 5-year period (1986 to 1990) were abstracted, and information concerning sex, age, race, birthplace, sibship size, birth order, maternal age at birth, month of birth, duration of breast-feeding, and maternal smoking was recorded. Medical records of patients presenting at the respective pediatric gastroenterology departments immediately before or after the patients with inflammatory bowel disease were seen were also abstracted in order to generate a control series. Data concerning 68 patients with Crohns disease, 39 patients with ulcerative colitis, and 202 control patients were analyzed through multiple logistic regression. Breast-feeding was negatively associated with Crohns disease (P approximately 0.04) and ulcerative colitis (P approximately 0.07), with relative risk point estimates around 0.5 and with evidence of duration-dependent trends in both instances. There was no evidence of association of either disease with maternal age at birth, birth order, maternal smoking, or season of birth.

Successful Use of Pooled Sera to Estimate HIV Antibody Seroprevalence and Eliminate All Positive Cases

Pooling specimens when testing them in large numbers can save scarce resources and several earlier reports have indicated this to be a feasible strategy. In an HIV antibody mass screening test carried out in our laboratory, we used Dorfmans two-stage model. We sought to establish the optimal number of specimens in a pool, and to achieve maximum efficiency while maintaining both sensitivity and specificity. Before testing for HIV antibody, five positive samples were placed in a set of 1012 sera in a double blind manner, one positive sample into a second set of 1012 sera and none in a third set The positive rate was assumed to be 0.2% for each set of 1012 sera. As indicated by our model, 22 individual serum samples were placed into each of 46 pools which, when tested by particle agglutination assays, lead to the identification of all positive samples. We concluded that the prevalence rate can be estimated in the first stage, 95% confidence intervals were given, and the efficiency rate could be calculated for the identification of all infected specimens in a large number of samples showing low prevalence rates.

Strategies for blood screening for the hepatitis C virus and for the human immunodeficiency virus in high risk groups.

For many infectious agents, seroprevalence rate is low but has serious consequences and must therefore be kept out of donated blood supplies. However, screening to ensure the safety of blood supplies has an associated very high cost. Forexample, in blood banks, detection of all the harmful items in a large number of samples is an expensive and tedious process. The larboratory and statistical approaches to ob-tain significant savings by the pooling method were discussed from 1943, recently, there have been further discussions of pooling sera as a means to determining the HIV seroprevalence rate in the general population or the weed out all HIV-positive individuals in blood screening. Here we describe a simple mathematical method to weed out all HIV, and HCV seropositive units. The method is designed to max-imize possible savings. Two examples illustrate the application of this method in determining the number to be pooled in each stage, and the resluting savings. When the prevalence rate is lower than 2 precent. our method offers savings of over 80 percent.

Efficiency gains from the use of sample pooling technique: a theoretical example of dengue virus detection in vector.

Testing large numbers of specimens for viral antigens, antibodies, requires a great deal of manpower, time and money. Therefore it would be useful if testing could be performed with the specimens pooled. However, how to establish the optimal number of specimens to be pooled to achieve the maximum efficiency while maintaining both sensitivity and specificity is a question that needs to be answered. In this study, we developed a mathematical model and procedure to resolve this problem. We estimated a saving rate of over 98% for an assumed infection rate of 1/10000 by testing the sample in pools of 100-101 specimens. The saving rate decreases with increasing infection rates, until there is probably no efficiency gain achieved for infection rates greater than 30%. Tests of infection in pooled mosquitoes were assumed to be free of viruses other than the dengue virus to interfere with detection. Heads of Aedes mosquitoes were first pooled and squashed, and the extract obtained was injected by intrathoracic inoculation into Toxorhynchites amboinensis, a biological amplifier of dengue antigen. Sensitivity was not reduced. Therefore, this pooling technique is useful for determining the optimal number of specimens in a pool, calculating an exact infection rate, and for identifying specific infected specimens in tests of a large number of samples showing low rates of infection in our theoretical example.