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Biomedical subjects

N Rifai

Publications and source records attributed to N Rifai.

At least 91 records · Page 5Linked to original sources
PubMed1999

Glycosylated hemoglobin and risk of colorectal cancer and adenoma (United States).

OBJECTIVES: The consistently observed epidemiologic associations of obesity and physical activity with colorectal cancer and precursor adenoma risk suggest that insulin and glucose control may be contributory. We evaluated the association of glycosylated hemoglobin (HbA1c), a clinical indicator of average glycemia over the previous 2 months, and possibly, indirectly, a marker of average blood insulin level, with colorectal carcinogenesis. METHODS: Among women in the Nurses' Health Study, who provided blood in 1989-90 and were diagnosed subsequently in 1989-94, we included 79 colorectal cancer cases and 156 matched controls, and 201 distal colorectal adenoma cases and 201 matched controls. HbA1c concentrations in red blood cells were determined blindly by turbidometric immunoinhibition. Odds ratios (OR) and 95% confidence intervals (CI) were estimated from conditional logistic regression models. RESULTS: HbA1c level did not significantly differ between colorectal cancer cases (median 5.5%) and controls (5.5%, p = 0.5), although a small difference between adenoma cases (5.6%) and controls (5.5%, p = 0.06) was noted. Compared to the lowest tertile of HbA1c (median 5.2%), women in the middle (median 5.5%, OR = 1.2, CI = 0.6-2.5) and upper (5.8%, OR = 1.2, CI = 0.6-2.7) tertiles were not at an increased risk for colorectal cancer. A modestly elevated risk of distal colorectal adenoma in the upper (median 5.8%, OR = 1.4, CI = 0.9-2.3) versus lower (median 5.3%) tertile could not be excluded. These associations were not appreciably altered after adjusting for known and suspected colorectal cancer risk factors. CONCLUSION: Over the range of levels observed in this relatively small sample of middle-aged women, prediagnostic HbA1c does not clearly predict colorectal cancer and adenoma risk.

Adenoma↗
PubMed1999

Plasma concentrations of interleukin-6 and abdominal aortic diameter among subjects without aortic dilatation.

Previous studies suggest that cytokine-induced tissue inflammation may participate in the pathogenesis of abdominal aortic aneurysms. Serum inflammatory markers may reflect arterial inflammation in asymptomatic phases of the aneurysmal disease. We studied 120 outpatients (62 men; age, 65+/-9 years) by ultrasound evaluation of the abdominal aorta to evaluate the association of circulating levels of interleukin-6 (IL-6) with abdominal aortic diameter in subjects with normal aortic size. Aortic diameter was measured at the infrarenal level and indexed for body surface area. Seven patients with abdominal aortic dilatation (indexed aortic diameter, >1.3 cm/m2) were also identified. Plasma concentrations of IL-6, serum amyloid A (SAA), C-reactive protein (CRP), total homocysteine, and lipids were measured. Among the 113 subjects without aortic dilatation, indexed aortic diameter was positively associated with serum levels of IL-6 (P<0.01), SAA (P<0.01), and total homocysteine (P=0.01). IL-6 levels increased in a stepwise fashion among dichotomized groups of aortic size (low and high aortic diameters) and peaked in patients with aortic dilatation (2.3+/-1.2 versus 2. 7+/-0.9 versus 3.2+/-0.9 pg/mL, respectively; P for trend=0.039). None of the serum lipid measurements correlated with abdominal aortic diameter. Although CRP levels were associated with SAA levels (r=0.60; P<0.001), associations between CRP and aortic diameter were nonsignificant. In multivariate analysis, levels of IL-6 (P=0.02), SAA (P=0.001), and total homocysteine (P<0.001) were independent correlates of indexed aortic diameter. In conclusion, circulating levels of IL-6, SAA, and total homocysteine may reflect processes involved in the early phases of abdominal aortic aneurysm formation, before dilation of the abdominal aorta is established. These data support a role for chronic inflammation in the progression of asymptomatic aortic disease.

Aged↗
PubMed1999

Acute changes in serum lipids and lipoprotein subclasses in triathletes as assessed by proton nuclear magnetic resonance spectroscopy.

Exercise is associated with changes in lipids that may protect against coronary heart disease (CHD). In this study of 28 triathletes, we analyzed acute changes in serum lipid and lipoprotein concentrations after completion of the 1995 World Championship Hawaii Ironman Triathlon. With standard laboratory assays, we demonstrate significant decreases in total cholesterol, VLDL cholesterol, ApoB100, and Lp(a). Total HDL cholesterol increased significantly immediately after the race. With a novel proton NMR spectroscopy assay, we demonstrate that smaller diameter LDL particles, corresponding to small, dense LDL, declined by 62%. Moreover, larger HDL subclasses, whose levels are inversely associated with CHD, increased significantly by 11%. Smaller HDL subclasses, which have been directly associated with CHD in some studies, acutely decreased by 16%. Therefore, exercise not only acutely induces changes in lipoprotein concentrations among the standard species in a manner that favorably affects CHD risk, but also induces favorable changes in specific lipoprotein subclass size distribution that also may alter CHD risk independently of the total lipoprotein serum concentration.

Adult↗
PubMed1999

Correlation between serum levels of cardiac troponin-T and the severity of the chronic cardiomyopathy induced by doxorubicin.

PURPOSE: To investigate, over a wide range of cumulative doxorubicin doses, the feasibility of using serum concentrations of cardiac troponin-T (cTnT) as a biomarker for doxorubicin-induced myocardial damage. MATERIALS AND METHODS: Groups of spontaneously hypertensive rats (SHR) were given 1 mg/kg doxorubicin weekly for 2 to 12 weeks. Cardiomyopathy scores were assessed according to the method of Billingham and serum levels of cTnT were quantified by a noncompetitive immunoassay. Myocardial localization of cTnT was studied by immunohistochemical staining and confocal microscopy. RESULTS: Increases in serum levels of cTnT (0.03 to 0.05 ng/mL) and myocardial lesions (cardiomyopathy scores of 1 or 1.5) were found in one out of five and two out of five SHR given 2 and 4 mg/kg doxorubicin, respectively. All animals given 6 mg/kg or more of doxorubicin had increases in serum cTnT and myocardial lesions. The average cTnT levels and the cardiomyopathy scores correlated with the cumulative dose of doxorubicin (0.13 v 0.4 ng/mL cTnT and scores of 1.4 v 3.0 in SHR given 6 and 12 mg/kg doxorubicin, respectively). Decreased staining for cTnT was observed in cardiac tissue from SHR receiving cumulative doses that caused only minimal histologic alterations (scores of 1 to 1.5). Staining for cTnT decreased simultaneously with increases in the severity of the cardiomyopathy scores. CONCLUSION: cTnT is released from doxorubicin-damaged myocytes. Measurements of serum levels of this protein seem to provide a sensitive means for assessing the early cardiotoxicity of doxorubicin.

Animals↗
PubMed1999

Inflammation, the acute phase response and atherosclerosis.

There is increasing evidence that atherosclerosis is a chronic inflammatory disorder resulting from a combination of processes, and that acute exacerbations of this inflammation are associated with the acute coronary syndromes such as myocardial infarction and unstable angina. Measurement of the serum level of acute phase proteins, such as C-reactive protein and serum amyloid A protein, has been used to predict the risk of acute events in patients with atherosclerosis. Prospective studies have shown that higher serum acute phase protein levels, often within the reference range, are associated with increased risk of myocardial infarction (MI), stroke or peripheral vascular disease and predict risk of infarction and death among high-risk patients. These observations have important implications for the assessment of patients and for treatment.

Acute-Phase Reaction↗
PubMed1999

International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) Standardization Project for the Measurement of Lipoprotein(a). Phase 2: selection and properties of a proposed secondary reference material for lipoprotein(a).

The International Federation of Clinical Chemistry and Laboratory Medicine Working Group for the Standardization of Lipoprotein(a) Assays has initiated a project to select a secondary reference material for lipoprotein(a) that can standardize the measurement of this lipoprotein. Most of the analytical problems with lipoprotein(a) assays are due to apolipoprotein(a) kringle 4 type 2 reactive antibodies and values being expressed in mg/l mass units rather than as nmol/l of apolipoprotein(a) particles. In Phase 2, four manufactured materials were compared for analytical performance, commutability properties and method harmonization in 27 lipoprotein(a) test systems. Results of precision and linearity testing were comparable for all materials whereas testing for the harmonization effect resulted in an among-assay coefficient of variation for corrected lipoprotein(a) values of between 11% and 22%. The material that gave maximum harmonization achieved a variation of < 8% for 18 immunonephelometric and immunoturbidimetric assay systems. It can be hypothesized that this residual variation in part takes into account the inaccuracy of lipoprotein(a) measurement due to apolipoprotein(a) size polymorphism. On the basis of acceptable analytical performance, maximal harmonization effect and documented stability, a lyophilized material has been selected as the common calibrator for lipoprotein(a) to be used in a value transfer procedure by diagnostic companies.

Evaluation Studies as Topic↗
PubMed1999

Inflammatory markers in men with angiographically documented coronary heart disease.

BACKGROUND: Recent evidence suggests that atherosclerosis is a chronic inflammatory process. In this study, we examined several markers of inflammation in men with coronary heart disease (CHD) and appropriate controls. METHODS: The concentrations of C-reactive protein (CRP), serum amyloid A (SAA), interleukin-6 (IL-6), and soluble intracellular adhesion molecule (sICAM-1) were examined in 100 men with angiographically documented CHD and 100 age-, gender-, and smoking-matched controls with no history of CHD. We assessed the association of these markers with severity of disease as indicated by >50% obstruction in one vessel (n = 30), two vessels (n = 39), or three vessels (n = 31). RESULTS: Significant increases were noted in serum CRP (median for cases vs controls, 3.4 vs 1.5 mg/L; P <0.0001), SAA (5.9 vs 3.7 mg/L; P <0.005), and IL-6 (2.3 vs 1.7 ng/L; P <0. 013) in patients with CHD compared with controls. These differences remained significant after correction for age, smoking, hypertension, diabetes, and lipid and homocysteine concentrations. Plasma sICAM-1 was not significantly different between the two groups (335 vs 339 microg/L). No significant correlation was seen between these markers and the severity of coronary disease. CONCLUSIONS: Concentrations of CRP, SAA, and IL-6 were increased in patients with CHD but failed to correlate with severity of coronary disease. These markers might reflect the diffuse atherosclerotic process in the vascular system rather than the degree of localized obstruction from coronary lesions.

Adult↗
PubMed1999

Clinical efficacy of an automated high-sensitivity C-reactive protein assay.

BACKGROUND: Prospective studies have shown that C-reactive protein (CRP) can be used to predict risk of future cardiovascular events. High-sensitivity methods for CRP (hs-CRP) measurement are needed for this purpose. METHODS: We compared the clinical efficacy of an automated and commercially available latex-enhanced assay (Latex) for hs-CRP (Dade Behring) to a validated in-house ELISA, previously shown to predict future peripheral arterial disease (PAD) in asymptomatic populations. Using a prospective, nested, case-control design, we measured baseline hs-CRP concentrations in 144 apparently healthy men who subsequently developed symptomatic PAD and 144 age- and smoking habit-matched controls who remained free of vascular disease over the follow-up period of 60 months. RESULTS: The two hs-CRP assays correlated highly (r = 0.95; P <0.001), and all but two participants were classified into concordant quartiles or varied by only one quartile. The median hs-CRP of the case group was significantly higher than that of controls when measured by either the ELISA (1.34 vs 0.99 mg/L; P = 0.034) or the Latex method (1.80 vs 1.20 mg/L; P = 0.042). Furthermore, for both ELISA and the Latex method, the calculated relative risks of developing PAD increased significantly with each increasing quartile of hs-CRP. The calculated interquartile increase in relative risk of PAD was 31% (95% confidence interval, 5.2-62.2%; P = 0.01) for ELISA and 34% (95% confidence interval, 8.2-66.1%; P = 0.007) for the Latex method. CONCLUSIONS: Our findings indicate that the Latex method is equally as efficacious as the validated ELISA in classifying patients into cutoff points established by prospective studies for risk stratification for coronary and cerebrovascular disease.

Aged↗
PubMed1998

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.

Aged↗
PubMed1998

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.

Animals↗
PubMed1998

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.

Adolescent↗
PubMed1998

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.

Aged↗
PubMed1998

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.

Angina, Unstable↗
PubMed1998

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.

Aging↗
PubMed1998

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.

Adolescent↗
PubMed1998

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.

Aged↗
PubMed1998

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.

Biological Assay↗