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There is an increasing trend to apply gas chromatography combined with mass spectrometry (GC-MS) or liquid chromatography tandem mass spectrometry (LC-MS/MS) assay methods to large-scale epidemiologic studies for the measurement of serum sex steroids. These methods are generally considered the gold standard for sex steroid measurements because of their accuracy, sensitivity, turnaround time, and ability to assess a more complete panel of steroid metabolites in the same run. In this report, we evaluated the precision, including within-batch (intra) and between-batch (inter) reproducibility, of steroid hormone measurements determined by GC-MS and LC-MS/MS assays and RIA and compared measurements among these methods. Specifically, 282 overnight fasting serum samples from 20 male volunteers were analyzed for 12 steroid metabolites by GC-MS or LC-MS/MS in one lab over a 4-month period. Six of the analytes were also measured by RIA in another lab. Unconjugated hormones, including testosterone, dihydrotestosterone, dehydroepiandrosterone, androstenedione, androst-5-ene-3B,17B-diol, estrone, and estradiol, were measured by GC-MS, whereas conjugated hormones, including DHEA sulfate, androsterone glucuronide, 5A-androstane-3A,17B-diol 3-glucuronide, 5A-androstane-3A,17B-diol 17-glucuronide, and estrone sulfate, were measured by LC-MS/MS. A subset of these hormones, including testosterone, dihydrotestosterone, androstenedione, 5A-androstane-3A,17B-diol 17-glucuronide, estrone, and estradiol, were also measured by RIA following extraction and chromatography. We used the coefficient of variation (CV) and the intraclass correlation coefficient (ICC) to assess within-and between-batch assay variations. For the 12 analytes measured by GC-MS or LC-MS/MS, CVs and ICCs for within-and between-batch measurements were similar, with CVs ranging from 6.1% to 21.4% and ICCs ranging from 87.6% to 99.2%. The six analytes measured by RIA had good CVs and ICCs, with CVs <10% and ICCs >70% (range, 71.7-99.7%). For the six metabolites that were measured by both methods, the CVs were similar, whereas the ICCs were generally higher with the GC-MS method. The absolute values for each analyte measured by RIA and GC-MS differed, with RIAs usually yielding markedly higher levels than GC-MS, although the Pearson and Spearman correlation coefficients for these six analytes were near one and all were significant (P < 0.001). Our results show that RIA, GC-MS, and LC-MS/MS assays for androgens and estrogens in the two labs included in the study have good reproducibility, as measured by small CVs (<15%) and high ICCs (>80%), with the exception of estradiol (71.7%) when measured by RIA. Despite substantial differences in absolute measurements of sex steroid hormones by RIA and MS methods, correlations between the two assays for the six sex steroids measured in the two labs were high (>0.9). However, it is important for future large epidemiologic studies to incorporate MS with high reproducibility and specificity to measure a more complete profile ...

No abstract

Background-Lower-extremity peripheral arterial disease (PAD) is associated with decreased functional status, diminished quality of life, amputation, myocardial infarction, stroke, and death. Nevertheless, public knowledge of PAD as a morbid and mortal disease has not been previously assessed. Methods and Results-We performed a cross-sectional, population-based telephone survey of a nationally representative sample of 2501 adults Ն50 years of age, with oversampling of blacks and Hispanics. The survey instrument measured the demographic, risk factor, and cardiovascular disease characteristics of the study population; prevalent leg symptoms; PAD awareness relative to atherosclerosis risk factors and other cardiovascular and noncardiovascular diseases; perceived causes of PAD; and perceived systemic and limb consequences of PAD. Respondents were 67.2Ϯ12.6 years of age with a high prevalence of risk factors but only a modest burden of known coronary or cerebrovascular disease. Twenty-six percent of respondents expressed familiarity with PAD, a rate significantly lower than that for any other cardiovascular disease or atherosclerosis risk factor. Within the "PAD-aware" cohort, knowledge was poor. Half of these individuals were not aware that diabetes and smoking increase the risk for PAD; 1 in 4 knew that PAD is associated with increased risk of heart attack and stroke; and only 14% were aware that PAD could lead to amputation. All knowledge domains were lower in individuals with lower income and education levels. Conclusions-The public is poorly informed about PAD, with major knowledge gaps regarding the definition of PAD, risk factors that lead to PAD, and associated limb symptoms and amputation risk. The public is not aware that PAD imposes a high short-term risk of heart attack, stroke, and death. For the national cardiovascular disease burden to be reduced, public PAD knowledge could be improved by national PAD public education programs designed to reduce critical knowledge gaps.