Analysis of cocaine, benzoylecgonine, ecgonine methyl ester, ethylcocaine and norcocaine in human urine using HPLC with post-column ion-pair extraction and fluorescence detection.

The measurement of cocaine and its major metabolites has been achieved by an HPLC method that compensates for their different solubilities and detection properties. Although ecgonine methyl ester is a major metabolite it is generally not measured by HPLC because it is poorly detectable by UV, and its water solubility makes recovery from urine difficult. Using modified solid-phase extraction procedures recoveries of 85% for ecgonine methyl ester, 97% for cocaine, 106% for benzoylecgonine and 80% for ethylcocaine have been obtained from urine. Increased chromatographic retention and detection sensitivity has been obtained by formation of the t-butyldimethylsilyl derivative of ecgonine methyl ester which was found to be stable in the HPLC mobile phase for at least 1 week. Alkylation of norcocaine and benzoylecgonine has improved their detection sensitivity and also chromatographic resolution. All calibrations were linear over the range 200-1000 ng ml-1 in urine with correlation coefficients > 0.99.     

Residents can be trained to detect abdominal aortic aneurysms using personal ultrasound imagers: a pilot study.

Our objective was to test the hypothesis that internal medicine residents can be trained to screen for abdominal aortic aneurysm (AAA) using personal ultrasound imagers. We trained 5 randomly chosen internal medicine residents to image the abdominal aorta for patients with risk factors for AAAs using personal ultrasound imagers. Residents were trained in 3 or 4 one-on-one sessions with an instructor. To be eligible, patients had to be older than 65 years and have hypertension. After training, each of the 5 residents studied 3 patients independently. In 12 of the residents' 15 unsupervised studies, their abdominal aorta measurements were within 5 mm of the instructor's measurements with standard echocardiography (mean difference 3 mm, range 0-6 mm). Residents detected 3 previously unknown AAAs measuring 5.2, 4.2, and 3.9 cm in diameter. We conclude residents can be trained to image the abdominal aorta with personal ultrasound imagers and to identify AAAs in patients at risk.     

Assessing the validity of childhood blood pressure screening: unbiased estimates of sensitivity, specificity, and predictive values.

Blood pressure measurement in childhood can be considered as a screening test for future blood pressure levels. Evaluating this test involves calculating sensitivities, specificities, and predictive values for a blood pressure measurement at an initial time for predicting underlying true blood pressure at a subsequent time. We demonstrate the use of childhood blood pressure tracking correlations that are corrected for within-person variability to calculate unbiased estimates of these test characteristics. In a cohort of 333 schoolchildren, we measured blood pressure on multiple visits in each of 4 successive years. Using these data for within-person variances and corrected tracking correlations, and U.S. population data for means and total variances, we tabulated positive predictive values, sensitivities, and specificities for the case of predicting a 9-year-old male's true systolic blood pressure 3 years later. For example, if a 9-year-old's average blood pressure from 4 visits is 115 mmHg, the probability of his true blood pressure being greater than 116 mmHg (90th percentile) at age 12 is 0.50. With longer follow-up, the use of predictive values, sensitivities, and specificities that incorporate corrected correlations should allow determination of the accuracy of predicting adult blood pressure from childhood values, and therefore the usefulness of screening children for those at high risk of developing hypertension.