Circulating cell adhesion molecules are correlated with ultrasound-based assessment of carotid atherosclerosis

Although cellular adhesion molecules (CAMs) are hypothesized to play an important role in atherogenesis, the relationship between CAMs and systemic atherosclerosis is uncertain. Among 92 outpatients (48 men; mean+/-SD age, 65+/-9 years), we evaluated the association of soluble vascular CAM-1 (sVCAM-1) and intercellular adhesion molecule-1 (sICAM-1) with carotid intimal-medial thickness (IMT), an index of early atherosclerosis. All subjects underwent a 2-dimensional ultrasound examination of both carotid arteries at the distal common carotid arteries and bifurcation. sVCAM-1 and sICAM-1 levels measured by enzyme-linked immunosorbent assay were significantly correlated with mean IMT of the common carotid artery (r=0.34 and r=0.30, respectively; P<0.01) and carotid bifurcation (r=0.31 and r=0.26, respectively; P<0.05), whereas sVCAM-1 was also positively associated with maximal carotid IMT (r=0.35, P<0.01). Adjustment for age attenuated the association between sVCAM-1 and common (r=0.16, P=0.13) and bifurcation (r=0.18, P=0.07) carotid IMT but had minimal effect on the associations between sICAM-1 and carotid measurements (r=0.32, P<0.01; r=0.23, P<0.05; for common and bifurcation IMT, respectively). Age-adjusted sICAM-1 levels increased in a stepwise fashion across common carotid IMT tertiles (253+/-27 versus 275+/-24 versus 384+/-26 pg/mL for the lowest, intermediate, and highest IMT tertiles, respectively; P<0.01). A similar trend was also found between sVCAM-1 levels and common carotid IMT tertiles (625+/-60 versus 650+/-53 versus 714+/-58 pg/mL; P<0.15). These associations were minimally affected in analyses adjusting for hypertension, diabetes, smoking, low and high density lipoprotein cholesterol, lipoprotein(a), and homocysteine, or in a subgroup analysis limited to those with no prior history of atherothrombotic disease. These data demonstrate a positive association between serum CAMs with carotid IMT and further support the hypothesis that systemic inflammation may have a role in atherosclerotic lesion development.

Sciatic nerve blockade in infant, adolescent, and adult rats: a comparison of ropivacaine with bupivacaine

BACKGROUND

Ropivacaine is a newly introduced local anesthetic. No data are available regarding its safety, efficacy, or sensory-selectivity in children. The sciatic block duration and systemic toxicity of bupivacaine and ropivacaine were compared among infant, adolescent, and adult rats.

METHODS

Infant, adolescent, and adult rats received blocks with ropivacaine or bupivacaine. Nociceptive, proprioceptive, and motor blockade were assessed. Systemic effects (contralateral leg analgesia, seizures, respiratory distress, apnea) were quantified. Plasma local anesthetic concentrations were measured at terminal apnea.

RESULTS

Nerve blockade for a given absolute dose lasted longer in infants than in older rats for both drugs. Block duration from ropivacaine generally was the same as or slightly shorter than bupivacaine. There was no difference in sensory-selectivity between the drugs. Doses required to induce all systemic toxicity indices were inversely related to age (e.g., the lethal dose in 50% of animals [LD50] of ropivacaine in infants is 155 mg/kg; in adults it is 54 mg/kg). All indices of toxicity occurred at higher doses per kilogram for ropivacaine than bupivacaine, at all ages (e.g., the LD50 of bupivacaine in infants is 92 mg/kg; in adults it is 30 mg/kg). Plasma concentrations at terminal apnea were higher for ropivacaine than for bupivacaine at all ages, and were higher in infants than in older rats.

CONCLUSIONS

Ropivacaine resembles bupivacaine in its local anesthetic effects but has a greater margin of safety. For a given absolute dose, sciatic blockade in infant rats lasts longer than in adolescents or adults. Although the doses (in milligrams per kilogram) causing toxicity were much higher in infants than in adults, this probably does not correspond to a wider therapeutic index.

Analytical evaluation of particle-enhanced immunonephelometric assays for C-reactive protein, serum amyloid A and mannose-binding protein in human serum

Against a background of growing interest in more sensitive assays for quantifying various acute phase proteins, we evaluated the performance of recently developed tests for C-reactive protein (CRP), serum amyloid A (SAA) and mannose-binding protein (MBP) on the Behring nephelometer II (BNII). Sample results outside the calibration ranges of 3.5 to 220 mg/L for CRP, 3.3 to 215 mg/L for SAA and 0.09 to 5.6 mg/L for MBP were automatically re-measured at another dilution. The lower limits of detection were 0.01, 0.7 and 0.01 mg/L for CRP, SAA and MBP, respectively. The coefficients of variation (CV) for intra- (n > or = 20) and inter- (n > or = 15) assay precision were < 5.2% and < 8.5%, respectively, for the three proteins at concentrations representing low, normal and high. Linearity for each method was within 5% of the expected values throughout the calibration range. We observed no significant interference from bilirubin (up to 300 mg/L) or haemoglobin (up to 10 g/ L) for the three tests. Method comparison studies performed for CRP and SAA yielded the following results: y (CRP on BNII) = 0.75x (ELISA, Hemagen) -0.25 mg/L (r = 0.981, Sy/x = 2.1 mg/L; y (SAA on BNII) = 1.44x (ELISA, Hemagen) -9.9 mg/L (r = 0.972, Sy/x = 6.9 mg/L), where ELISA is enzyme-linked immunosorbent assay. Reference intervals established in 261 adult blood donors (aged 36.2 +/- 9.0 years) were found to be log-normal with 2.5th, 50th, and 97.5th centiles of < 0.17, 1.00 and 10.1 mg/L for CRP, < 0.84, 2.10 and 9.70 mg/L for SAA; and 0.30, 1.28 and 4.10 mg/L for MBP. We observed no relationship with CRP concentration and age; however, SAA levels increased with age while MBP levels decreased. The BNII provides a simple, rapid and sensitive system for measuring CRP, SAA and MBP in human serum.

Inflammation, pravastatin, and the risk of coronary events after myocardial infarction in patients with average cholesterol levels. Cholesterol and Recurrent Events (CARE) Investigators

BACKGROUND

We studied whether inflammation after myocardial infarction (MI) is a risk factor for recurrent coronary events and whether randomized treatment with pravastatin reduces that risk.

METHODS AND RESULTS

A nested case-control design was used to compare C-reactive protein (CRP) and serum amyloid A (SAA) levels in prerandomization blood samples from 391 participants in the Cholesterol and Recurrent Events (CARE) trial who subsequently developed recurrent nonfatal MI or a fatal coronary event (cases) and from an equal number of age- and sex-matched participants who remained free of these events during follow-up (control subjects). Overall, CRP and SAA were higher among cases than control subjects (for CRP P=0.05; for SAA P=0.006) such that those with levels in the highest quintile had a relative risk (RR) of recurrent events 75% higher than those with levels in the lowest quintile (for CRP RR= 1.77, P=0.02; for SAA RR= 1.74, P=0.02). The study group with the highest risk was that with consistent evidence of inflammation (elevation of both CRP and SAA) who were randomly assigned to placebo (RR=2.81, P=0.007); this risk estimate was greater than the product of the individual risks associated with inflammation or placebo assignment alone. In stratified analyses, the association between inflammation and risk was significant among those randomized to placebo (RR=2.11, P=0.048) but was attenuated and nonsignificant among those randomized to pravastatin (RR=1.29, P=0.5).

CONCLUSIONS

Evidence of inflammation after MI is associated with increased risk of recurrent coronary events. Therapy with pravastatin may decrease this risk, an observation consistent with a nonlipid effect of this agent.

Determination of serum physiological concentration of methylmalonic acid by gas chromatography-mass spectrometry with selected ion monitoring

We developed a sensitive assay for the rapid determination of serum methylmalonic acid concentration using capillary gas chromatography-mass spectrometry (GC/MS) with selected ion monitoring and a simple solid-phase extraction. The assay was linear up to 10,000 nmol/L and had a detection limit < 50 nmol/L, average recovery of 98% and between-day coefficient of variation at concentrations of 570 and 2206 nmol/L of 7.7% and 5.4%, respectively (n = 25). Comparison with another validated GC/MS method using sera with a wide range of methylmalonic acid concentrations (94-2020 nmol/L) revealed a slope and intercept of 0.97 and 17 nmol/L, respectively (n = 38). Methylmalonic acid concentrations determined by this assay in a group of apparently healthy individuals ranged from 64-331 nmol/L (n = 81). We conclude that the method is ideally suited for the determination of methylmalonic acid at physiological concentrations in both clinical and research laboratories.

International Federation of Clinical Chemistry standardization project for the measurement of lipoprotein(a). Phase I. Evaluation of the analytical performance of lipoprotein(a) assay systems and commercial calibrators

A secondary reference material for lipoprotein(a) is required to standardize the measurement of lipoprotein(a) in clinical laboratories worldwide. Towards this aim, the International Federation of Clinical Chemistry Working Group for the Standardization of Lipoprotein(a) Assays has initiated a standardization project involving a total of 33 diagnostic company and clinical chemistry laboratories from 12 countries. In Phase 1, the analytical performance of 40 lipoprotein(a) assay systems was evaluated by testing sera and manufactured lipoprotein(a) calibrator materials for precision, linearity, and parallelism. Twenty test systems were nonoptimized according to the results for a pooled serum, which tested nonlinear in 16 systems and imprecise in 4. Acceptable analytical properties and harmonization of lipoprotein(a) values were shown by some commercial calibrators, suggesting their possible use as reference materials. This study highlights the problems that currently occur for lipoprotein(a) measurement in existing assay systems.

Utility of direct measurement of low-density lipoprotein cholesterol in dyslipidemic pediatric patients

BACKGROUND

Low-density lipoprotein cholesterol (LDL-C) levels are the primary basis for treatment guidelines established for hyperlipidemic children and adolescents. Levels of LDL-C are commonly monitored by means of the Friedewald formula, an indirect calculation that requires an overnight fast. A new method has been developed for the direct measurement of LDL-C (DLDL-C) that does not require fasting. We evaluated the clinical utility of this method.

DESIGN

We determined LDL-C concentrations simultaneously by the DLDL-C method, Friedewald equation, and beta-quantification (reference procedure).

SETTING

Pediatric dyslipidemia clinic at Children's Hospital, Boston, Mass.

PATIENTS

Ninety-two fasting hyperlipidemic pediatric patients.

RESULTS

At the LDL-C concentration cutoffs commonly used for making therapeutic decisions, the DLDL-C method had a significant negative bias (P< or =.05) and misclassified patients into incorrect treatment groups more often than the Friedewald method. The negative predictive value for the DLDL-C method was lower than that for the Friedewald method (P< or =.05), and the cost of determining LDL-C level with the new method was 3 times greater.

CONCLUSIONS

The misclassification potential for LDL-C, and the assay costs, were greater for the DLDL-C method than for the Friedewald calculation. Despite the apparent advantages of the DLDL-C method, we conclude that for hyperlipidemic children the utility of this new method is not advantageous over the conventional Friedewald method. In some conditions, such as in diabetes or marked hypertriglyceridemia, the DLDL-C method may be useful.

Assessment of interlaboratory performance in external proficiency testing programs with a direct HDL-cholesterol assay

Direct assays for the determination of HDL-cholesterol (HDL-C) have recently become available. The methods are precise, require small sample volume, and appear to be less affected by increased triglycerides than traditional precipitation methods. In this study, we describe the inter- and intralaboratory variability of the Boehringer Mannheim Corporation direct HDL-C assay and its performance in external proficiency testing surveys. A comparison study among three laboratories, using different analyzers and 85 serum specimens, showed a correlation coefficient (r) of 0.99. The direct HDL-C assay also showed good agreement with the ultracentrifugation-dextran sulfate-Mg2+ method (r = 0.98) and the Cholesterol Reference Method Laboratory Network-Designated Comparison Method (a = 0.98x + 4.75 mg/L, r = 0.98). Total error at medical decision levels ranged from -0.8% to +11.1%. Furthermore, this assay performed adequately in the College of American Pathologists and the ALERT surveys as well as the CDC Lipid Standardization Program and met all performance criteria of regulatory agencies.

Early high dose antioxidant vitamins do not prevent bronchopulmonary dysplasia in premature baboons exposed to prolonged hyperoxia: a pilot study

The antioxidant vitamins ascorbic acid (AA) and alpha-tocopherol (alpha-TP) effectively inhibit oxygen free radical-induced lipid peroxidation. Using a premature baboon model of hyperoxia-induced bronchopulmonary dysplasia (BPD), we measured concentrations of AA, alpha-TP, and conjugated dienes (CD, marker of lipid peroxidation) in four animals (hyperoxic antioxidant group) receiving high dose antioxidant vitamin supplementation (AA, 100 mg x kg x(-1) x d(-1); alpha-TP; 20 mg x kg x(-1) x d(-1)) and one animal receiving standard dose antioxidant vitamin supplementation (AA, 10 mg x kg x(-1) x d(-1); alpha-TP, 1 mg x kg x(-1) x d(-1)). Respiratory and histopathologic data were compared with data from 10 historical animals exposed to hyperoxia (hyperoxic control group) and 11 historical animals treated as required with oxygen (normoxic control group) who had received standard dose antioxidant vitamin supplementation. Compared with standard dose antioxidant vitamin supplementation, high dose antioxidant vitamin supplementation effectively raised AA concentrations in plasma (37 +/- 22 micromol/L and 395 +/- 216 micromol/L, respectively) and tracheal aspirates (62 +/- 35 micromol/L and 286 +/- 205 micromol/L, respectively), and alpha-TP concentrations in plasma (10.1 +/- 2.5 micromol/L and 24.6 +/- 17.5 micromol/L, respectively). However, there was no apparent effect on tracheal aspirate CD concentrations (482 +/- 333 micromol/L and 1050 +/- 1111 micromol/L, respectively), and respiratory parameters in the hyperoxic antioxidant group were comparable to those of the hyperoxic control group but significantly worse than in the normoxic control group. Finally, no protective effect of high dose antioxidant vitamin supplementation was noted at the histopathologic level.

Analytical and clinical performance of a homogeneous enzymatic LDL-cholesterol assay compared with the ultracentrifugation-dextran sulfate-Mg2+ method

LDL-cholesterol (LDL-C) concentration is currently determined in most clinical laboratories by the Friedewald calculation. This approach has several limitations and may not meet the current total error requirement in LDL-C measurement of < or = 12%. We evaluated the analytical and clinical performance of the direct N-geneous LDL-C assay (Equal Diagnostics). The N-geneous method correlated highly with the modified beta-quantification assay (r = 0.95; y = 0.91x + 70.6 mg/L; n = 199), showed no significant effect of increased triglyceride or other common interferants, and performed adequately in serum samples from nonfasting individuals. This assay demonstrated a mean total error of 6.75% over a wide range of LDL-C concentrations. In addition, at the medical decision cutoff points, this LDL-C assay showed positive predictive values of 78-95% and negative predictive values of 84-99%. We conclude that the N-geneous LDL-C meets the currently established analytical performance goals and appears to have a role in the diagnosis and management of hypercholesterolemic patients.

C-reactive protein is a potent predictor of mortality independently of and in combination with troponin T in acute coronary syndromes: a TIMI 11A substudy. Thrombolysis in Myocardial Infarction

OBJECTIVES

We evaluated C-reactive protein (CRP) alone and in conjunction with a rapid qualitative assay for cardiac-specific troponin T (cTnT) for predicting 14-day mortality in patients with unstable angina or non-Q wave myocardial infarction (NQMI).

BACKGROUND

Elevated CRP has been found to correlate with higher risk for cardiac events in patients with coronary disease.

METHODS

At enrollment into the Thrombolysis in Myocardial Infarction (TIMI) 11A trial, a dose-ranging trial of enoxaparin for unstable angina and NQMI, serum was obtained for CRP measurement and rapid cTnT assay.

RESULTS

Quantitative CRP and rapid cTnT assays were performed in all patients. CRP was higher among patients who died than in survivors (7.2 vs. 13 mg/dl, p = 0.0038). The probability of a positive rapid cTnT assay rose with increasing CRP concentration (p < 0.0001). Among patients with a negative rapid cTnT assay, the mortality rate was higher among patients with CRP > or = 1.55 mg/dl (5.80% vs. 0.36%, p = 0.006). Patients with both an early positive rapid cTnT assay (< or = 10 min until assay positive) and CRP > or = 1.55 mg/dl had the highest mortality, followed by those with either CRP > or = 1.55 mg/dl or an early positive rapid cTnT assay, whereas patients with both a negative rapid cTnT assay and CRP < 1.55 mg/dl were at very low risk (9.10% vs. 4.65% vs. 0.36%, p = 0.0003).

CONCLUSIONS

Elevated CRP at presentation in patients with unstable angina or NQMI is correlated with increased 14-day mortality, even in patients with a negative rapid cTnT assay. Quantitative CRP and a rapid cTnT assay provide complementary information for stratifying patients with regard to mortality risk.

Time to positivity of a rapid bedside assay for cardiac-specific troponin T predicts prognosis in acute coronary syndromes: a Thrombolysis in Myocardial Infarction (TIMI) 11A substudy

OBJECTIVES

We sought to determine whether the rapid bedside assay for troponin T identified patients at risk for a more complicated hospital stay and a higher rate of adverse clinical events.

BACKGROUND

In patients with an acute coronary syndrome, the amount of cardiac-specific troponin T released bears a stoichiometric relation to the extent of myocardial damage.

METHODS

In 597 patients with unstable angina or non-Q wave myocardial infarction participating in the Thrombolysis in Myocardial Infarction (TIMI) 11A substudy, a rapid bedside assay and simultaneous quantitative serum measurement for troponin T were obtained at enrollment.

RESULTS

The composite end point of the sum of death, nonfatal myocardial infarction or recurrent ischemia through day 14 occurred in 33.6% of patients with a positive assay compared with only 22.5% of patients with a negative assay (p = 0.01). Those patients in whom the rapid assay became positive in < or = 10 min had the highest mortality rate of 4.2% through day 14 compared with 1.1% in those patients who had either a late-appearing positive assay (> 10 min) or a negative assay. The duration of hospital stay in the 116 patients (19%) with a positive rapid assay at enrollment was a median of 5 days compared with only 3 days in the 481 patients (81%) with a negative rapid assay at enrollment (p = 0.002).

CONCLUSIONS

A positive rapid assay for troponin T at presentation identifies those patients at risk for higher rates of adverse clinical events and longer, more complicated hospital stays. Stratification of patients by time to development of a positive rapid assay identifies those patients at highest mortality risk.

Vitamins A and E serum levels in children and young adults with inflammatory bowel disease: effect of disease activity

BACKGROUND

Hypovitaminosis and fat-soluble vitamin deficiency have been reported in adults with inflammatory bowel disease (IBD). A prospective study was undertaken to determine the prevalence of low serum levels of vitamins A and E in children and young adults with IBD.

METHODS

Clinical information and serum for vitamin levels was gathered prospectively from 61 patients with Crohn's disease, 36 patients with ulcerative colitis, and 23 control subjects. Disease activity and disease location were determined for IBD patients. Serum retinol and alpha-tocopherol levels were determined by high-performance liquid chromatography.

RESULTS

The prevalence of hypovitaminosis A (defined as serum vitamin A < 20 micrograms/dl) or hypovitaminosis E (defined as serum vitamin E < 5 mg/l) was 16% in the pediatric IBD population studied. Low vitamin A levels were more common than low vitamin E levels. Serum retinol levels correlated significantly with alpha-tocopherol levels. Hypovitaminosis was significantly more prevalent in the Crohn's disease patients who had active disease, an erythrocyte sedimentation rate of more than 25 mm/hour, or a serum albumin level less than 3 mg/dl.

CONCLUSIONS

Children and young adults with active IBD frequently have low serum levels of vitamin A or vitamin E. The severity of disease activity is a better predictor of risk for hypovitaminosis than is nutritional status. Further work is necessary to determine whether the hypovitaminosis seen in children with IBD reflects true deficiency.

Use of cardiac troponin T levels as an indicator of doxorubicin-induced cardiotoxicity

The release of cardiac troponin T (cTnT) as a biomarker of doxorubicin-induced chronic cardiac injury was evaluated in the spontaneously hypertensive rat (SHR) model. Elevations in serum levels of cTnT and decreased immunohistochemical staining of heart sections for this protein were noted in SHRs treated with cumulative doses of doxorubicin (7 mg/kg) that induced only minimal histological alterations in myocytes. Concentrations of cTnT were further elevated, coincident with reduced immunohistochemical staining, in SHRs given 10-12 mg/kg doxorubicin. Thus, monitoring serum levels of cTnT can detect doxorubicin-induced myocyte damage in SHR and may prove useful for the noninvasive evaluation of this toxicity in humans.

Evaluation and clinical application of a direct low-density lipoprotein cholesterol assay in normolipidemic and hyperlipidemic adults

This study examines the performance and clinical use of a commercial immunoseparation assay for low-density lipoprotein (LDL) cholesterol in a sample population of normolipidemic and hyperlipidemic adult volunteers. Using paired fasting and nonfasting samples, we compared the direct LDL assay with the beta quantification method and the Friedewald calculation. Overall, the direct LDL assay correctly classified 82% and 60% of fasting and nonfasting subjects, respectively, into National Cholesterol Education Program risk groups. The Friedewald method correctly classified 84% of subjects. The fasting direct LDL assay has comparable positive and negative predictive values to the Friedewald method, except at an LDL cholesterol of 100 mg/dl. The nonfasting direct LDL assay demonstrates unacceptable positive predictive values when LDL cholesterol decreases to the 130 to 159 and > or = 160 mg/dl categories. Overall, direct LDL assay demonstrates limitations in the nonfasting state and at the LDL cholesterol level of 100 mg/dl used for patients with established coronary heart disease.

Predictive value of cardiac troponin T in pediatric patients at risk for myocardial injury

BACKGROUND

Biochemical markers have not been routinely used in children at risk for myocardial damage. Yet, because of somatic growth and the duration of survival, a low level of myocardial damage may ultimately be of more consequence in children than in adults.

METHODS AND RESULTS

We investigated the utility of cardiac troponin T (cTnT) blood levels (CARDIAC T ELISA Troponin T, Boehringer Mannheim Corp) in 51 consecutively sampled patients from 1 day to 34 years of age (median=5.7 years) undergoing cardiovascular (n=19) or noncardiovascular (n=17) surgery or who received doxorubicin for acute lymphoblastic leukemia (ALL) (n=15). Minimum detectable cTnT elevations were 0.03 ng/mL. cTnT was measurable in children of all ages with myocyte damage. In patients who underwent cardiovascular surgery, a correlation was noted between a score of increasing surgical severity and the mean level of postoperative cTnT (r=.79, P<.0001). Postoperative cTnT levels were elevated in children who completed cardiovascular surgery with an open chest compared with those with a closed chest (P=.0083). In addition, cTnT levels before cardiovascular surgery predicted postoperative survival (P=.007). cTnT elevations were observed after initial doxorubicin therapy for ALL. The magnitude of elevation predicted left ventricular dilatation (r=.80 when variables were treated as continuous, P=.003) and wall thinning (r=.61, P=.044) 9 months later.

CONCLUSIONS

Elevations of blood cTnT in children relate to the severity of myocardial damage and predict subsequent subclinical and clinical cardiac morbidity and mortality.

Three generations of high-density lipoprotein cholesterol assays compared with ultracentrifugation/dextran sulfate-Mg2+ method

We report on the analytical performance of three generations of HDL-cholesterol assays: phosphotungstic acid/Mg2+, Spinpro, and a homogeneous method, N-geneous. The run-to-run imprecision (CV) of all assays was < or = 4.9%, and all results correlated highly with those of a modified reference procedure (r > or = 0.96). At triglycerides concentrations < 4000 mg/L, these field methods showed an acceptable systematic error (y = 1.12x - 47, 1.05x - 23, and 0.96x + 8 for the phosphotungstate, Spinpro, and N-geneous assays, respectively), and the total error of the field methods met the current National Cholesterol Education Program (NCEP) performance goal of < or = 22%. Regression analyses of results for samples with triglycerides > 4000 mg/L produced the following results for the above respective assays: y = 1.08x - 4.2, 1.02x + 3.6, and 0.85x + 108. In this hypertriglyceridemic group, only the N-geneous assay (at an HDL-cholesterol content of 240 mg/L) had a total error (35%) that exceeded the NCEP limit. Bilirubin and ascorbate produced a negative interference with the phosphotungstate and Spinpro assays but had little effect on the N-geneous assay.

Measurement of plasma ketoprofen by a rapid high-performance liquid chromatography assay

The authors developed a high performance liquid chromatography assay for the determination of plasma ketoprofen concentration using a single-step extraction, a short chromatographic separation of 3 min, and a sample volume of 50 microliters. The assay possessed linearity up to 500 mg/l, sensitivity down to at least 1 mg/l, average recovery of 100.1%, and run-to-run precision (n = 20) of 4.6% at a level of 10 mg/l and 2.2% at a level of 40 mg/l. Furthermore, the assay was free of interference from 51 prescription and over-the-counter medications. The authors conclude that the method described here is ideally suited for the determination of ketoprofen concentration in a clinical laboratory setting for the purpose of therapeutic monitoring and assessment of toxicity.

Measurement of plasma busulfan concentration by high-performance liquid chromatography with ultraviolet detection

Busulfan is widely used in bone marrow transplantation. Increased area under the plasma concentration curve has been shown to correlate with venoocclusive disease, which occurs in approximately 20% of these patients. The authors developed a high performance liquid chromatography assay for the determination of plasma busulfan concentration using ultraviolet detection and a single-step derivatization and extraction. The absolute retention times of busulfan and the internal standard were 2.8 and 5.6 min, respectively. The assay possessed linearity up to 200 mumol/l, sensitivity to at least 0.2 mumol/l, average recovery of 101%, and run-to-run precision (n = 34) of < 7%. Furthermore, the assay proved to be free of interference from 59 medications and correlated highly with a validated method employing gas chromatography with electron capture detection (slope = 0.90, intercept = 0.17, r = 0.98, n = 31). The authors conclude that the method described here is ideally suited for the therapeutic monitoring of busulfan.

Use of a rapid HPLC assay for determination of pharmacokinetic parameters of ibuprofen in patients with cystic fibrosis

High doses of ibuprofen have been shown to delay the progression of lung disease without serious adverse effects in patients with cystic fibrosis. To be effective, peak ibuprofen concentration of 50 to 100 mg/L has to be achieved. We developed an HPLC assay to rapidly determine plasma ibuprofen concentration. We used this assay to determine the pharmacokinetics of ibuprofen in patients with cystic fibrosis. The assay possessed linearity up to 500 mg/L, sensitivity to 1 mg/L, average recovery of 98%, and run-to-run precision (n = 23) of 3%. Furthermore, the assay proved to be free of interference from 51 medications. Observed time to peak concentration varied significantly between those receiving ibuprofen tablets (mean + SD, 94 +/- 29 min, n = 16) and syrup (30 +/- 0 min, n = 4) (P < 0.0001). We conclude that the method described here is ideal for therapeutic monitoring of ibuprofen.

Use of a rapid HPLC assay for determination of pharmacokinetic parameters of ibuprofen in patients with cystic fibrosis

High doses of ibuprofen have been shown to delay the progression of lung disease without serious adverse effects in patients with cystic fibrosis. To be effective, peak ibuprofen concentration of 50 to 100 mg/L has to be achieved. We developed an HPLC assay to rapidly determine plasma ibuprofen concentration. We used this assay to determine the pharmacokinetics of ibuprofen in patients with cystic fibrosis. The assay possessed linearity up to 500 mg/L, sensitivity to 1 mg/L, average recovery of 98%, and run-to-run precision (n = 23) of 3%. Furthermore, the assay proved to be free of interference from 51 medications. Observed time to peak concentration varied significantly between those receiving ibuprofen tablets (mean + SD, 94 +/- 29 min, n = 16) and syrup (30 +/- 0 min, n = 4) (P &lt; 0.0001). We conclude that the method described here is ideal for therapeutic monitoring of ibuprofen.

Vitamin A status in acute exacerbations of cystic fibrosis

Vitamin A is an essential nutrient for epithelial cell maintenance and repair, and it is known that infectious stresses may depress plasma vitamin A concentrations. Patients with cystic fibrosis are at risk for vitamin A deficiency because of fat malabsorption as well as for the inflammatory stresses of pulmonary exacerbations of their underlying disease. We therefore hypothesized that acute pulmonary exacerbations of CF would depress plasma retinol concentrations, and that these concentrations would return to baseline values when clinical symptoms improved. We prospectively studied 35 CF patients (mean age: 24.2 y) consecutively admitted with pulmonary exacerbations. Plasma retinol, vitamin E, retinol binding protein (RBP), and C-reactive protein (CRP) concentrations were measured on hospital admission and discharge. Dietary intake was measured by using a semiquantitative food-frequency questionnaire. Regression analysis was used to identify significant clinical and laboratory correlates of retinol concentrations. On admission, mean (+/- SD) concentrations of plasma retinol were 1.14 +/- 0.5 mumol/L compared with 1.70 +/- 0.6 mumol/L on discharge (P = 0.0001). Of 35 subjects, 8 (22.9%) had plasma retinol concentrations considered to be in the deficient range (< 0.70 mumol/L). Concurrently, mean concentrations of plasma RBP increased during hospital admission (from 1.46 to 2.24 mumol/L, P = 0.003), and the mean CRP concentration declined (from 25.7 to 9.8 mg/L, P = 0.002). Significant positive correlations were found between plasma retinol concentrations at admission and age, weight, body mass index, triceps-skinfold-thickness percentile, midupper arm circumference percentile, plasma vitamin E, and RBP concentration, thus suggesting that better-nourished patients had more optimal vitamin A status. At admission, plasma retinol concentrations were negatively correlated with maximum body temperature and CRP concentrations, which indicated that the body's acute-phase response was associated with the depression in retinol concentrations. We conclude that plasma retinol concentrations are depressed in acute pulmonary exacerbations of cystic fibrosis, and that concentrations considered to be in the deficient range are common. Vitamin A metabolism during acute inflammatory stress deserves further study.

Failure of current guidelines for cholesterol screening in urban African-American adolescents

OBJECTIVE

The National Cholesterol Education Program (NCEP) and the American Academy of Pediatrics recommend selective screening to detect children and adolescents with hypercholesterolemia. We compared the effectiveness of these guidelines with other potential screening strategies in urban African-American adolescents.

SUBJECTS AND METHODS

Two hundred sixty African-American adolescents and young adults (192 females and 68 males; age range, 12 to 20 years) who were free from illnesses or medications that disrupt lipid metabolism were included in the study. Participants completed a questionnaire regarding their smoking habits, blood pressure, contraceptive pill use, and family history of early heart disease and high cholesterol and had their blood lipids, lipoproteins, and apolipoproteins measured (152 fasting and 108 nonfasting).

RESULTS

Nineteen percent of participants reported family histories of hypercholesterolemia; 26% reported family histories of premature heart disease; and 8% had family histories of both hypercholesterolemia and premature heart disease. Therefore, 37% of these participants would have been targeted for cholesterol screening, compared with the 25% predicted by the NCEP. Less than 50% of the participants with low-density lipoprotein cholesterol (LDL-C) levels greater than 110 or 130 mg/dL would have been detected by selective screening. Total cholesterol was superior as a screening test to apolipoprotein B in predicting LDL-C levels greater than 110 mg/dL (sensitivity, 92% vs 59%). However, total cholesterol minus high-density lipoprotein cholesterol showed better positive predictive value (100%) at LDL-C levels greater than 110 mg/dL than total cholesterol in the fasting (80%) and total groups (90%).

CONCLUSIONS

In this population, selective screening with total cholesterol, as recommended by the NCEP, has such poor sensitivity and positive predictive value that other options may be superior. As an alternative, we recommend the measurement of high-density lipoprotein cholesterol together with total cholesterol at the initial screening step in adolescents and universal screening for those older than 16 years to capture a greater proportion of young adults with increased LDL-C. Furthermore, we recommend using the less stringent treatment guidelines established by the Adult Treatment Panel II for premenopausal women and men younger than 35 years for older adolescents and young adults.

Analytical performance and clinical utility of a direct LDL-cholesterol assay in a hyperlipidemic pediatric population

This study compares a new latex immunoseparation method for the direct determination of plasma low-density lipoprotein cholesterol (LDL-C) with the reference procedure for LDL-C (beta-quantification) in a pediatric hyperlipidemic population. The direct LDL-C assay has a mean bias of -98 mg/L in a fasting group (n = 96) of patients (mean triglycerides 1057 +/- 720 mg/L) and a bias of +177 mg/L in a nonfasting group (n = 42, mean triglycerides 4854 +/- 5457 mg/L). The mean total analytical error calculated from our data is 13.8%. The direct LDL-C assay and the commonly used Friedewald calculation respectively classified 81% and 84% of fasting patients correctly, according to the cutoffs of 1100 and 1300 mg/L for LDL-C set by the National Cholesterol Education Program for pediatric patients. Of combined fasting and nonfasting patients, 80% were correctly classified by the direct LDL-C assay. Therefore, despite several analytical shortcomings, the direct LDL-C assay may be useful in managing hyperlipidemic children without the need for a fasting specimen.

Effects of a single bout of ultraendurance exercise on lipid levels and susceptibility of lipids to peroxidation in triathletes

OBJECTIVE

To determine the effects of a single bout of ultraendurance exercise, as a model for physiologic stress, on lipid and lipoprotein levels, and oxidative susceptibility of lipids in highly trained athletes.

DESIGN

Observational trial.

POPULATION AND SETTING

Thirty-nine volunteer subjects (26 mean, 13 women; mean age, 38 +/- 10 years) who competed in and completed the 1994 Hawaii Ironman World Championship Triathlon consisting of a consecutive 3.9-km (2.4-mi) swim, 180.2-km (112-mi) bike ride, and a 42.2-km (26.2-mi) run. Subjects answered questionnaires and had blood samples obtained 2 days prior to and within 15 minutes of completion of the triathlon.

MAIN OUTCOME MEASURES

Prerace vs postrace changes in lipid and lipoprotein levels, and susceptibility of lipids to peroxidation.

RESULTS

The mean duration of exercise was 753 +/- 128 minutes. With exercise, plasma volume-corrected levels of triglycerides decreased 39% from 1.58 +/- 0.83 to 0.97 +/- 0.68 mmol/L (139.6 +/- 73.6 to 85.8 +/- 60.5 mg/dL) (P < .001). Levels of total cholesterol decreased 9% from 4.94 +/- 0.88 to 4.50 +/- 0.79 mmol/L (190.8 +/- 33.8 to 173.8 +/- 30.6 mg/dL) (P < .001), low-density lipoprotein cholesterol decreased 11% from 2.59 +/- 0.77 to 2.30 +/- 0.86 mmol/L (100.1 +/- 29.9 to 88.7 +/- 33.3 mg/dL) (P = .02), and apolipoprotein B decreased 10% from 0.91 +/- 0.20 to 0.82 +/- 0.18 g/L (90.7 +/- 20.0 to 82.0 +/- 17.9 mg/dL) (P < .001). High-density lipoprotein cholesterol and apolipoprotein A-I increased with exercise but not significantly. The susceptibility of lipids to peroxidation decreased significantly (4.51 +/- 1.91 micromol/L, preexercise, vs 2.42 +/- 2.27 micromol/L, postexercise, P < .001), an effect that was not related to antioxidant use or levels of vitamins A, C, or E. Serum iron, a potential pro-oxidant, also decreased by 45% with exercise from 15.75 +/- 5.55 to 8.59 +/- 4.30 micromol/L (88 +/- 31 to 48 +/- 24 micrograms/dL) (P < .001), an effect that was weakly correlated with changes in lipid peroxidation (P = .05).

CONCLUSIONS

These data suggest that a single bout of prolonged exercise can reduce lipid and lipoprotein risk factors for developing cardiovascular disease. Moreover, susceptibility of lipids to peroxidation is reduced by exercise, thereby adding to the benefits of physical activity. This effect appears to be independent of antioxidant supplement use and may be mediated by induction of endogenous antioxidants. These observations may explain in part the reduced risk of developing vascular and other diseases in individuals who are physically active.

Three routine methods for measuring high-density lipoprotein cholesterol compared with the Reference Method

We compared the performance of three methods for quantifying high-density lipoprotein cholesterol (HDL-C) with the Reference Method for HDL-C, using samples with a wide range of triglyceride (TG) concentrations (290-18000 mg/L). All three comparison assays-- utilizing a magnetic dextran sulfate precipitating reagent, a direct method, and a standard MgCl2-dextran sulfate reagent--were precise, with a run-to-run CV of less than or equal to 4.1%. However, the systematic error of these assays exceeded the National Cholesterol Education Program (NCEP) performance goal of less than or equal to 10% in half of the concentration ranges tested. Nevertheless, the total error of the assays generally meets the current 22% limit set by the NCEP. Although both the magnetic dextran sulfate precipitation reagent and the direct assay can be performed more rapidly than the MgCl2-dextran sulfate assay, the direct assay involves no sample preparation and requires only 4 microL of sample excluding the dead space. Although precipitation is frequently inadequate with the MgCl2-dextran sulfate reagent at TG concentrations &gt;6000 mg/L, both the magnetic and the direct reagent show no interference from high TG concentrations as great as 18 000 mg/L.

Three routine methods for measuring high-density lipoprotein cholesterol compared with the Reference Method

We compared the performance of three methods for quantifying high-density lipoprotein cholesterol (HDL-C) with the Reference Method for HDL-C, using samples with a wide range of triglyceride (TG) concentrations (290-18000 mg/L). All three comparison assays-- utilizing a magnetic dextran sulfate precipitating reagent, a direct method, and a standard MgCl2-dextran sulfate reagent--were precise, with a run-to-run CV of less than or equal to 4.1%. However, the systematic error of these assays exceeded the National Cholesterol Education Program (NCEP) performance goal of less than or equal to 10% in half of the concentration ranges tested. Nevertheless, the total error of the assays generally meets the current 22% limit set by the NCEP. Although both the magnetic dextran sulfate precipitation reagent and the direct assay can be performed more rapidly than the MgCl2-dextran sulfate assay, the direct assay involves no sample preparation and requires only 4 microL of sample excluding the dead space. Although precipitation is frequently inadequate with the MgCl2-dextran sulfate reagent at TG concentrations >6000 mg/L, both the magnetic and the direct reagent show no interference from high TG concentrations as great as 18 000 mg/L.

The role of lipoproteins in the transport and uptake of cyclosporine and dihydro-tacrolimus into HepG2 and JURKAT cell lines

OBJECTIVES

We wish to examine the role of lipoproteins in the transport and cellular uptake of cyclosporine (CsA) and tacrolimus.

DESIGN AND METHODS

The distribution of tritiated CsA and tacrolimus among lipoproteins was determined in normo- and hypertriglyceridemic sera. The uptake of these two drugs into HepG2 and JURKAT cell lines was assessed in the presence of various concentrations of low density lipoproteins. (LDL).

RESULTS

Our data showed that about 60% of these drugs were transported by high density lipoprotein in normolipidemic sera, while about 50-60% were carried by very low density lipoprotein in hypertriglyceridemic sera. Almost 80% of CsA and 70% of tacrolimus entered HepG2 and JURKAT cells within the first hour of incubation in lipoprotein free media. However, the uptake was decreased (CsA by 60% and tacrolimus by 40%) in the presence of LDL.

CONCLUSIONS

Lipoproteins play a major role in the transport of CsA and tacrolimus, but not in their cellular uptake.

Therapy with oral clotrimazole induces inhibition of the Gardos channel and reduction of erythrocyte dehydration in patients with sickle cell disease

Pathologic water loss from sickle erythrocytes concentrates the abnormal hemoglobin and promotes sickling. The Ca2+-activated K+ channel (Gardos channel) contributes to this deleterious dehydration in vitro, and blockade of K+ and water loss via this channel could be a potential therapy in vivo. We treated five subjects who have sickle cell anemia with oral clotrimazole, a specific Gardos channel inhibitor. Patients were started on a dose of 10 mg clotrimazole/kg/d for one week. Protocol design allowed the daily dose to be escalated by 10 mg/kg each week until significant changes in erythrocyte density and K+ transport were achieved. Blood was sampled three times a week for hematological and chemical assays, erythrocyte density, cation content, and K+ transport. At dosages of 20 mg clotrimazole/kg/d, all subjects showed Gardos channel inhibition, reduced erythrocyte dehydration, increased cell K+ content, and somewhat increased hemoglobin levels. Adverse effects were limited to mild/moderate dysuria in all subjects, and a reversible increase in plasma alanine transaminase and aspartic transaminase levels in two subjects treated with 30 mg clotrimazole/kg/d. This is the first in vivo evidence that the Gardos channel causes dehydration of sickle erythrocytes, and that its pharmacologic inhibition provides a realistic antisickling strategy.

Evaluation of the APEC analyzer for whole blood glucose. Testing in a pediatric setting

The APEC glucose analyzer (APEC, Danvers, MA) was analyzed in a pediatric clinical chemistry laboratory and its performance was compared with glucose determinations on the YSI 2300 STAT analyzer (Yellow Springs Instrument [YSI], Yellow Springs, OH). One hundred sixty-nine samples were simultaneously analyzed by the APEC and the YSI systems. The agreement between the two analyzers was excellent, with r = 0.986, slope = 1.04, and y intercept = -0.094. Analysis of the run-to-run precision yielded a CV of < or = 4.1% for both the APEC and the YSI instruments. Both analyzers displayed a sensitivity to at least 1.1 mmol/L (20 mg/dL) and both produced a linear response up to 27.8 mmol/L (500 mg/dL). Neither instrument was affected by icteric or hemolyzed samples. Variations in the patient's hematocrit did not lower the whole blood glucose values when these were compared with the equivalent plasma levels. In conclusion, the APEC glucose analyzer is suited for whole blood glucose testing in pediatric settings.

A high-performance liquid chromatographic assay for the determination of itraconazole concentration using solid-phase extraction and small sample volume

Itraconazole has been shown to be highly effective against a broad spectrum of fungi, particularly aspergillus. In order to achieve the desired pharmacological effect, the itraconazole plasma concentration should be > 250 ng/ml. We developed a high-performance liquid chromatography assay for the rapid determination of plasma itraconazole concentration using solid-phase extraction and small sample volume. The assay possessed linearity up to 5,000 ng/ml, sensitivity of 50 ng/ml, average recovery of 100.8%, and run-to-run precision (n = 10) for concentrations of 100, 200, and 500 ng/ml of 12, 6.6, and 5.8%, respectively. Furthermore, the assay proved to be free of interference from 48 commonly prescribed and some over-the-counter medications. We conclude that the method described here is ideally suited for the therapeutic monitoring of itraconazole.

Assessment of the immunoreactivity of digoxin metabolites and the cross-reactivity with digoxin-like immunoreactive factors in the Roche-TDM ONLINE digoxin assay

Immunoassays for digoxin measurement have long had the problem of low specificity. Antisera used in these assays may not only measure digoxin and the active metabolites but also cross-react with the noncardioactive metabolites and digoxin-like immunoreactive factors (DLIFs). In this study, we describe the analytical performance of the newly introduced Roche-TDM ONLINE digoxin assay on the COBAS FARA II centrifugal analyzer. The assay possessed linearity up to 5.0 ng/ml, sensitivity of 0.19 ng/ml, average recovery of 100.4%, and day-to-day variability of < 6%. The assay demonstrated no cross-reactivity with DLIFs or spironolactone and its metabolites and negligible reactivity with the digoxin noncardioactive metabolites. In addition, the immunoreactivity of the digoxin active metabolites reflected their cardioactivity. We conclude that the Roche-TDM ONLINE digoxin assay is highly specific and precise and suitable for the therapeutic monitoring of this drug.

Oral administration of clotrimazole and blockade of human erythrocyte Ca(++)-activated K+ channel: the imidazole ring is not required for inhibitory activity

The Ca(++)-activated K+ (Gardos) channel of erythrocytes plays a crucial role in K+ loss and dehydration of sickle erythrocytes; a potential therapeutic strategy would be to prevent dehydration by specifically blocking this channel. The authors report here on the activity of the clotrimazole (CLT) metabolite, 2-chlorophenyl-bis-phenyl-methanol, which accounts for a portion of the blockade of the erythrocyte Gardos channel when CLT is given orally to normal volunteers. Administration of a single oral dose of 1 g of CLT to four normal healthy volunteers (approximately 15 mg/kg of body weight) resulted in 51% to 92% peak inhibition of the Gardos channel measured in whole blood 2 to 4 hr later. Inhibition remained detectable for 24 to 34 hr. Inhibition of the Gardos channel correlated best with the summed levels of CLT plus its two major metabolites (P < .002; apparent IC50 = 0.65 +/- 0.19 microM). In vitro experiments with 2-chlorophenyl-bis-phenyl-methanol revealed dose-dependent inhibition of K transport and displacement of specifically bound 125I-charybdotoxin. Thus, the imidazole ring of CLT, which is required for antimycotic activity and associated with most of the historically observed toxicity, is not necessary for inhibition of the Gardos channel.

HPLC measurement, blood distribution, and pharmacokinetics of oral clotrimazole, potentially useful antisickling agent

Clotrimazole (CLT) has recently been shown to be a potent and specific inhibitor of the Ca(2+)-activated K+ channel and to thereby prevent K+ loss and cellular dehydration of sickled erythrocytes. This evidence suggests that oral CLT may be a useful new therapy for sickle cell disease. Here, we describe the development of an HPLC assay to measure CLT, a method we used to study the pharmacokinetics and transport of CLT in normal volunteers. The assay's linear range extended to 10 mumol/L; the detection limit was 0.1 mumol/L, analytical recovery 97.7%, and run-to-run imprecision (CV) &lt; 4.7%. In unaffected subjects, CLT concentration peaked within 6 h of oral administration and returned to close to baseline by 24 h. High-density lipoproteins appear to be the main carriers of this drug in both normo- and hypertriglyceridemic plasma. We conclude that the method described here is ideally suited for therapeutic monitoring of CLT concentrations.

HPLC measurement, blood distribution, and pharmacokinetics of oral clotrimazole, potentially useful antisickling agent

Clotrimazole (CLT) has recently been shown to be a potent and specific inhibitor of the Ca(2+)-activated K+ channel and to thereby prevent K+ loss and cellular dehydration of sickled erythrocytes. This evidence suggests that oral CLT may be a useful new therapy for sickle cell disease. Here, we describe the development of an HPLC assay to measure CLT, a method we used to study the pharmacokinetics and transport of CLT in normal volunteers. The assay's linear range extended to 10 mumol/L; the detection limit was 0.1 mumol/L, analytical recovery 97.7%, and run-to-run imprecision (CV) < 4.7%. In unaffected subjects, CLT concentration peaked within 6 h of oral administration and returned to close to baseline by 24 h. High-density lipoproteins appear to be the main carriers of this drug in both normo- and hypertriglyceridemic plasma. We conclude that the method described here is ideally suited for therapeutic monitoring of CLT concentrations.

Prolonged survival in pyruvate carboxylase deficiency: lack of correlation with enzyme activity in cultured fibroblasts

OBJECTIVE

To report the clinical history and laboratory evaluation of a patient presenting with lactic acidosis secondary to pyruvate carboxylase deficiency.

METHODS AND RESULTS

Enzyme analysis of cultured skin fibroblasts revealed 2-5% of normal pyruvate carboxylase activity. Although most patients with this condition die in early infancy, this child has survived to age 8-1/2 years, with only occasional episodes of metabolic acidosis, usually responding rapidly to intravenous hydration and bicarbonate. Despite having a seizure disorder and moderate mental retardation, he continues to thrive and make progress in his acquisition of motor and language skills. Of the 35 patients described in the literature with pyruvate carboxylase deficiency, only two other patients have lived beyond 5 years of age.

CONCLUSION

There does not seem to be a correlation of prolonged survival with residual pyruvate carboxylase activity on assay of cultured fibroblasts. Possible explanations for this patient's prolonged survival include tissue heterogeneity, increased residual enzyme activity in vivo, or partial stabilization of the enzyme by supplemental biotin.

Efficacy of felbamate in therapy for partial epilepsy in children

Thirty children (2 to 17 years of age) with refractory partial seizures received open-label felbamate as an add-on medication to their background antiepileptic drugs. The dose was increased up to a maximum of 45 mg/kg. Compared with baseline seizure activity, there was a 53% decrease in seizure frequency during felbamate therapy; 50% of the patients had more than a 50% decrease in seizure frequency. Patients older than 10 years of age were more likely to have a favorable response. Age correlated positively with felbamate concentrations and negatively with apparent felbamate clearance. Transient weight loss occurred in 57% of the patients; the weight loss was maximal after 12 weeks of initiation of felbamate, and subsided after the twentieth week of treatment. Anorexia and insomnia were reported in 20% and 16% of the patients, respectively. Adverse effects were generally tolerable; felbamate therapy was discontinued because of side effects in only one patient, because of a rash. We conclude that felbamate can be a useful and well-tolerated medication in the treatment of refractory partial epilepsy in children. However, increased apparent clearance of this drug in younger children should be considered in treatment of this age group.

Measurement of felbamate by wide-bore capillary gas chromatography and flame ionization detection

Felbamate, a newly developed antiepileptic agent, has been demonstrated to control partial and generalized seizures effectively. We have developed a gas-chromatographic method for the determination of felbamate, using a wide-bore capillary column, a flame ionization detector, and a simple extraction procedure. The assay day-to-day precision (n = 20) was 5.2% and 3.6% for drug concentrations of 50 and 150 mg/L, respectively; average recovery over a wide range of felbamate concentrations was 95%; the detection limit was 5 mg/L; and assay linearity extended to 300 mg/L. Although 9 of the 27 drugs tested were coextracted with felbamate, they exhibited significantly different retention times and showed no interference. A short-term stability study showed that plasma felbamate is stable at 4, -20, or -78 degrees C for at least 1 month. Plasma felbamate concentrations in 66 pediatric patients ranged from 7 to 154 mg/L (mean +/- SD 44 +/- 24.7). We consider the method ideally suited for therapeutic monitoring of plasma felbamate concentration.

Measurement of felbamate by wide-bore capillary gas chromatography and flame ionization detection

Felbamate, a newly developed antiepileptic agent, has been demonstrated to control partial and generalized seizures effectively. We have developed a gas-chromatographic method for the determination of felbamate, using a wide-bore capillary column, a flame ionization detector, and a simple extraction procedure. The assay day-to-day precision (n = 20) was 5.2% and 3.6% for drug concentrations of 50 and 150 mg/L, respectively; average recovery over a wide range of felbamate concentrations was 95%; the detection limit was 5 mg/L; and assay linearity extended to 300 mg/L. Although 9 of the 27 drugs tested were coextracted with felbamate, they exhibited significantly different retention times and showed no interference. A short-term stability study showed that plasma felbamate is stable at 4, -20, or -78 degrees C for at least 1 month. Plasma felbamate concentrations in 66 pediatric patients ranged from 7 to 154 mg/L (mean +/- SD 44 +/- 24.7). We consider the method ideally suited for therapeutic monitoring of plasma felbamate concentration.

Urinary N-acetyl-beta-glucosaminidase and beta-2-microglobulin in the diagnosis of urinary tract infection in febrile infants

Urinary N-acetyl-beta-glucosaminidase (NAG) and beta-2-microglobulin (B2M) concentrations were measured in 24 pediatric patients with febrile urinary tract infection (UTI) and compared with the technetium-99m-labeled dimercaptosuccinic acid (DMSA) renal scan results, in order to evaluate a noninvasive means to localize the site of UTI. Increased urinary B2M and NAG were not associated with renal inflammation (pyelonephritis), as defined by positive dimercaptosuccinic acid scan. Median NAG concentrations were 114.2 mumol/hour/mg creatinine (CR) (range, 5.7 to 305.4) in 17 febrile UTI patients vs. 13.8 (range, 3.4 to 104.3) in 17 age and sex-matched febrile controls with negative urine cultures, P = 0.0001. The sensitivity and specificity of NAG > or = 40 mumol/hour/mg of CR in predicting UTI in febrile patients, regardless of the site of infection, were 88 and 88%, respectively. Increased urinary NAG is associated with UTI in febrile patients regardless of the level of infection (scan status), and may be an informative indicator of UTI.

Serum lipids, neuroendocrine, and cardiovascular responses to stress in men and women with mild hypertension

In this study, we examined the relation between serum lipid levels, gender, and cardiovascular and neuroendocrine stress reactivity in patients with mild hypertension. Ninety-nine individuals (62 men, 37 women) with mild hypertension performed four mental stress tasks: mental arithmetic, public speaking, cold stress, and a computer videogame. Cardiovascular reactivity scores were computed by subtracting the minimum resting blood pressure (BP) and heart rate (HR) values from the maximum values obtained during each task. Neuroendocrine reactivity was calculated as the change from epinephrine and norepinephrine values from mean rest to mean task. High and low reactors were identified on the basis of median splits of reactivity scores, averaged across all four stressors. High systolic blood pressure reactors had higher levels of total (TC), low-density lipoprotein cholesterol (LDL-C), and apo-B than did low reactors. High diastolic blood pressure reactors had lower levels of high-density lipoprotein cholesterol (HDL-C) and higher levels of LDL-C and apo-B than did low reactors. High HR reactors had higher apo-AI:apo-AII ratios than low reactors. Lipid levels were not different for high and low epinephrine and norepinephrine reactors. Although women were noted to have more favorable lipid profiles than men, both male and female hypertensive patients who were high reactors had less favorable lipid profiles than low reactors.

Role of free radicals in cancer and atherosclerosis

As aerobic creatures, normal living requires that not only are human beings exposed to oxygen but are dependent on oxygen. Humans have evolved mechanisms to cope with living in an aerobic environment; however, modern humans may be more exposed to oxidant stresses. Much indirect evidence implicates reactive oxygen species in diseases such as cancer and atherosclerosis. There are also other diseases that are influenced by oxidative balance, including the normal process of aging. Common environmental factors that could cause oxidative stress include a low intake of dietary antioxidants, a high intake of polyunsaturated fatty acids, and exposure to ozone, ionizing radiation, and cigarette smoke. The recent development of overall measures of oxidant status, such as breath pentane; highly sophisticated measures, such as electron spin resonance and specific measures of base damage to DNA by mass spectrometry; and other methods will allow much more specific data to be collected on the importance of reactive oxygen species in many disease states. Such measures can serve as end points for a variety of studies in experimental animals and humans that will allow for the testing of many potential prooxidant and antioxidant compounds. Other important evidence will be available soon from, for example, large scale chemoprevention trials that are currently under way. As an indicator of the increased interest in oxidant balance, several reference laboratories now have nutritional biochemistry sections that offer measurement of specific free-radical scavenging enzymes. These enzyme measures complement the more routinely available measurements of trace element and antioxidant nutrients.

Incidence of lead poisoning in young children from inner-city, suburban, and rural communities

The Centers for Disease Control (CDC) have recently lowered the acceptable blood lead concentration in young children from < or = 25 to < or = 10 micrograms/dl (< or = 1.21 to < or = 0.48 mumol/L). The incidence of lead toxicity with respect to geographical areas and socioeconomic status has not yet been defined. We evaluated the incidence of increased lead concentration in inner-city, suburban, and rural children aged 9 months to 3 years. Seven hundred eighty of the 4,196 studied inner-city samples (18.6%) had lead concentrations > or = 10 micrograms/dl (0.48 mumol/L), of which only 71 (1.6%) had lead values > or = 25 micrograms/dl (1.21 mumol/L). Only 5 of the 212 studied children (2.4%) from suburbia and 7 of the 120 children (5.8%) from rural communities had blood lead concentrations > or = 10 micrograms/dl (0.48 mumol/L). None of these children, however, had a lead concentration > or = 15 micrograms/dl (0.73 mumol/L). In contrast, 276 inner-city subjects (6.6%) had lead values > or = 15 micrograms/dl (0.73 mumol/L). Our data indicate that a correlation exists between geographical location and blood lead concentration in young children. Government health agencies at all levels should prioritize their limited resources for those areas that are most at risk for lead poisoning.

Effective control of hypercholesterolemia in children with dietary interventions based in pediatric practice

BACKGROUND

Based on recent recommendations, the number of hypercholesterolemic children who would require dietary therapy could overwhelm current preventive pediatric cardiology resources. No previous studies have established the efficacy of such therapy in the pediatrician's office. The purpose of this study was to evaluate two programs of office-based therapy.

METHODS

We randomly assigned 295 children with hypercholesterolemia (> 185 mg/dl) two interventions: one single or four multiple 90-min sessions of family-oriented nutritional education, based in pediatric practices. We examined total cholesterol, 3-day food records, height and weight, and in the multisession group high-density lipoprotein cholesterol and triglycerides at the beginning and at intervals of 8.5-9 and 21 to 33 weeks (single-session and multisession groups, respectively).

RESULTS

Total cholesterol was lowered equally in both treatment groups over the course of the study. This was accompanied by dietary changes: a decrease in calories derived from total and saturated fats, and increased intake of fiber, protein, and carbohydrate. However, more single-session patients withdrew from the program during the study.

CONCLUSIONS

The two interventions were equally effective in lowering total and low-density lipoprotein cholesterol and in reducing intake of total and saturated fat. However, the higher completion rate of the multisession group suggests that this approach may be the more effective.