Total serum cholesterol by isotope dilution/mass spectrometry: a candidate definitive method

We describe a highly accurate and precise method for determination of total cholesterol in serum by isotope dilution/mass spectrometry. The method was developed for a Study Group of the Committee on Standards of the American Association for Clinical Chemistry, for use in establishing the accuracy of a candidate reference method for total cholesterol, and fulfills their criteria for a definitive method. Cholesterol-d7 is added to serum, with the weight ratio of cholesterol-d7 to total serum cholesterol kept near to 1:1. The esters are hydrolyzed and the cholesterol is separated and converted into the trimethylsilyl ether derivative for measurement by combined gas chromatography/mass spectrometry. The intensity ratio of the molecular ions at m/z 465 and 458 is measured for each sample and for two calibration mixtures, according to a prescribed bracketing protocol. A weight ratio for the sample is obtained by linear interpolation of the ion-intensity ratios, and the total cholesterol is then calculated. The method was applied four times over several weeks to each of five serum pools. Statistical analysis involving consideration of both replication error and variability between weeks gave a coefficient of variation for a single measurement of 0.36%. The absence of interferences in the method was demonstrated by measurements at several other masses.

Total serum cholesterol by isotope dilution/mass spectrometry: a candidate definitive method

We describe a highly accurate and precise method for determination of total cholesterol in serum by isotope dilution/mass spectrometry. The method was developed for a Study Group of the Committee on Standards of the American Association for Clinical Chemistry, for use in establishing the accuracy of a candidate reference method for total cholesterol, and fulfills their criteria for a definitive method. Cholesterol-d7 is added to serum, with the weight ratio of cholesterol-d7 to total serum cholesterol kept near to 1:1. The esters are hydrolyzed and the cholesterol is separated and converted into the trimethylsilyl ether derivative for measurement by combined gas chromatography/mass spectrometry. The intensity ratio of the molecular ions at m/z 465 and 458 is measured for each sample and for two calibration mixtures, according to a prescribed bracketing protocol. A weight ratio for the sample is obtained by linear interpolation of the ion-intensity ratios, and the total cholesterol is then calculated. The method was applied four times over several weeks to each of five serum pools. Statistical analysis involving consideration of both replication error and variability between weeks gave a coefficient of variation for a single measurement of 0.36%. The absence of interferences in the method was demonstrated by measurements at several other masses.

DAWN: a second look--its impact on minorities and public policy

Though various indicators yield different statistics about the minority component of drug problems, Blacks and Hispanics dominate opiate statistics of major data systems. This dominance increases when major consequences--chemotherapy, arrest and, especially, imprisonment--are measured. Drug Abuse Warning Network (DAWN) figures were cited as the exception, but this was due to weaknesses in DAWN reporting and its analysis by experts. Excluding unreliable and unrepresentative crisis center mentions, estimating the Hispanic component of "White" DAWN mentions, and separating opiates from other drugs, the DAWN statistics are very similar to CODAP and arrest statistics. "Hard drugs" remain an essentially minority phenomena.

Statistical evaluation of CAP survey results for calcium, potassium, and blood urea nitrogen

Throug the use of the statistical technic known as the linear model, a complete analysis has been made of data obtained in the Colleg of American Pathologists Survey of 1975 for calcium, potassium, and blood urea nitrogen (BUN). The analysis allows a separation of laboratories into core and non-core categories. It also allows for determination of the reproducibility of each analytic technic involved in this survey. For Ca and K, the results obtained by each analytic method were compared with the results obtained by the National Bureau of Standards through use of the definitive method. For BUN, the comparison was made with the average of values for all laboratories and all methods.

Epidemiologic study of prostatic cancer: preliminary report

In a preliminary report on a small fraction of the projected subject population, some evidence in support of both sexual activity and venereal transmission hypotheses is accumulating. Prostatic cancer cases, in contrast to hospitalized and/or neighborhood controls, are beginning to show greater proportions of selected sexual activities compatible with venereal transmission of an infectious agent, such as number of sexual partners, use of prostitutes, prior venereal disease, and genital infections in the spouse. Patients with prostatic cancer also appear to have had higher fertility and more prostatic cancer in blood relatives than controls. Age at first intercourse and at first marriage are lower among the cancer patients than among the controls. Antibody titrations for herpesvirus and cytomegalic virus, although currently not revealing striking disparities in positivity, tend to show higher titers among the cancer cases.

Investigating possible effects of abestos in city water: surveillance of gastrointestinal cancer incidence in Duluth, Minnesota

The recent discovery of over one million asbestos-like fibers per liter of Duluth tap water and the suggestive evidence of a link between certain gastrointestinal (GI) cancers and work exposure to asbestos fibers in the air prompted this study. GI cancer incidence data were gathered for Duluth in the same manner as data previously gathered for comparison cities, Minneapolis and St. Paul. Although some differences in GI cancer incidence occurred among the three cities in 1969-1971, there was no consistent pattern of statistically significant differences observed. The number of GI cancers diagnosed in Duluth residents in 1972 was similar to that in each of the previous three years. This study represents the start of ongoing cancer surveillance in Duluth.

Research for a Uniform Quality Grading System for Tires. III. Breaking Energy

A test procedure designed to classify tires according to their average breaking energy has been applied to a sample of passenger car tires. Data are reported on 127 different tires of all grades and types over a range of sizes. A scaling system is devised and applied to the data. It is found that the system leads to conclusions similar to those derived from the original data.

Research for a Uniform Quality Grading System for Tires. II. Wheel Speed Capability Test

The wheel speed capability of a tire is defined by a test method which determines the speed at which the tire fails on a laboratory test wheel. Data is reported on over 100 different passenger car tires of all grades and types over a range of sizes. A scaling system is devised for this property. It is found that the system produces consistent results for tires of given manufacturer's nominal grade across the size range tested and for samples produced several months apart.

Measurement of the Aging of Rubber Vulcanizates

Ultimate elongation (strain at failure) can be used to assess the aging of all rubber vulcanizates. For this purpose, it appears that Equation (2) can be used to express the early part of the aging process, corresponding to a period of aging at room temperature of 10 or more years. Prediction of shelf aging from tests at two or more elevated temperatures is only possible if the relationship between aging and temperature is known. For some rubber compounds the Arrhenius equation appears to hold. In these instances, it provides an effective means for estimating shelf aging.

Some Factors Influencing the Road Wear of Tires

Three road tests of tires for tread wear were statistically designed. The design of test equalized the treatment of tires, and included a study of some of the factors influencing the road wear of tires in addition to the primary object of the test. Among these factors were the effects of vehicle, wheel position, day of test, climatic conditions, and length of storage. A study was made also of two methods of measurement-depth of tread grooves and weight loss. The information on these factors was obtained at no increase in cost of test. It was found that atire loses weight at essentially a constant rate, whereas, the depth of the tread grooves decreases at a declining rate, which results in a bias in the tread wear ratings. The weight method was also found to be more sensitive than the depth method. The study of the effects of vehicle and wheel positions led to the conclusion that differences in the rate of wear on different wheels do not affect the tread wear comparisons, since the rate in slow wearing positions is proportional to that in fast wearing positions, and the coefficient of variation is about the same. These results led to the conclusion that geometric rather than arithmetic averages be used in evaluating tread wear. The study of the effect of day of testing and of climatic conditions indicated that the surface temperature of the road and tire has a pronounced effect on rate of wear. Natural rubber treads containing channel black wore faster as the temperature increased, whereas, synthetic rubber tread containing furnace blacks wore faster as the temperature decreased. Other treads wore at about the same rate as the temperature changed. The effect of temperature on tread wear was greater in many instances than the effect of a lower coefficient of friction on wet roadways. Storage of tires generally increased the rate of wear; however, some treads did not wear faster after one year of storage. The object of one test was to determine the effect of type of rubber and black on tread wear. It was found that the rubber and black are mutually independent in their effects. The behavior of natural and synthetic rubbers or of channel and furnace blacks with a change in temperature made it impossible to compare them without stating the conditions of test.