The effect of polymorphisms of MTHER gene and vitamin B on hyperhomocysteinemia

Recent studies have shown that moderate eleva-tion of plasma total homocysteine( Hcy) ,termedmoderate hyperhomocysteinemia was related to coro-nary artery disease ( CAD) [1,2 ] .Hcy is a thiol aminoacid generated from metabolism of methionine.There are two pathways in mammals:remethylationof Hcy to methionine and transsulfuration of it tocysteine,each accounting for about5 0 % of Hcy dis-posal.N5 ,N1 0 - methylenetetrahydrofolate reductase( MTHFR) and cystathionine-β- synthase ( CBS) ar…     

Periodic health examination, 1999 update: 1. Detection, prevention and treatment of obesity

OBJECTIVES: (1) To evaluate the evidence relating to the effectiveness of methods to prevent and treat obesity, and (2) to provide recommendations for the prevention and treatment of obesity in adults aged 18 to 65 years and for the measurement of the body mass index (BMI) as part of a periodic health examination. OPTIONS: In adults with obesity (BMI greater than 27) management options include weight reduction, prevention of further weight gain or no intervention. OUTCOMES: The long-term (more than 2 years) effectiveness of (a) methods to prevent obesity and (b) methods to treat obesity. EVIDENCE: MEDLINE was searched for articles published from 1966 to April 1998 that related to the prevention and treatment of obesity; additional articles were identified from the bibliographies of review articles and the listings of Current Contents. Selection criteria were used to limit the analysis to prospective studies with at least 2 years' follow-up. BENEFITS, HARM AND COSTS: Health benefits of weight reduction were evaluated in terms of alleviation of symptoms, improved management of obesity-related diseases and a reduction in major clinical outcomes. The health risk of weight-reduction methods were briefly evaluated in terms of increased mortality and morbidity. VALUES: The recommendations of this report reflect the commitment of the Canadian Task Force on Preventive Health Care to provide a structured, evidence-based appraisal of whether a manoeuvre should be part of a periodic health examination. RECOMMENDATIONS: (1) Prevention: There is insufficient evidence to recommend in favour of or against community-based obesity prevention programs; however, because of considerable health risks associated with obesity and the limited long-term effectiveness of weight-reduction methods, the prevention of obesity should be a high priority for health care providers (grade C recommendation). (2) Treatment: (a) For obese adults without obesity-related diseases, there is insufficient evidence to recommend in favour of or against weight-reduction therapy because of a lack of evidence supporting the long-term effectiveness of weight-reduction methods (grade C recommendation); (b) for obese adults with obesity-related diseases (e.g., diabetes mellitus, hypertension), weight reduction is recommended because it can alleviate symptoms and reduce drug therapy requirements, at least in the short term (grade B recommendation). (3) Detection: (a) for people without obesity-related diseases, there is insufficient evidence to recommend the inclusion or exclusion of BMI measurement as part of a periodic health examination, and therefore BMI measurement is left to the discretion of individual health care providers (grade C recommendation); (b) for people with obesity-related diseases, BMI measurement is recommended because weight reduction should be considered with a BMI of more than 27 (grade B recommendation). VALIDATION: The findings of this analysis were reviewed through an iterative process by the members of the Canadian Task Force on Preventive Health Care. SPONSORS: The Canadian Task Force on Preventive Health Care is funded through a partnership between the Provincial and Territorial Ministries of Health and Health Canada.     

Provision of preventive care to unannounced standardized patients

OBJECTIVE: To examine the relation between physician, training and practice characteristics and the provision of preventive care as described in the guidelines of the Canadian Task Force on the Periodic Health Examination. DESIGN: Cross-sectional study. SETTING: Family practices open to new patients within 1 hour's drive of Hamilton, Ont. PARTICIPANTS: A total of 125 family physicians were randomly selected from respondents to an earlier preventive care survey. Of the 125, 44 (35.2%) declined to participate, and an additional 19 (15.2%) initially consented but later withdrew when they closed their practices to new patients. Sixty-two physicians thus participated in the study. INTERVENTION: Unannounced standardized patients posing as new patients to the practice visited study physicians' practices between September 1994 and August 1995, portraying 4 scenarios: 48-year-old man, 70-year-old man, 28-year-old woman and 52-year-old woman. OUTCOME MEASURES: Proportion of preventive care manoeuvres carrying grade A, B, C, D and E recommendations from the Canadian Task Force on the Periodic Health Examination that were performed, offered or advised. A standard score was computed based on the performance of grade A and B manoeuvres (good or fair evidence for inclusion in the periodic health examination) and the non-performance of grade D and E manoeuvres (fair or good evidence for exclusion from the periodic health examination). RESULTS: Study physicians performed or offered 65.6% of applicable grade A manoeuvres, 31.0% of grade B manoeuvres, 22.4% of grade C manoeuvres, 21.8% of grade D manoeuvres and 4.9% of grade E manoeuvres. The provision of evidence-based preventive care was associated with solo (v. group) practice and capitation or salary (v. fee-for-service) payment method. Preventive care performance was unrelated to physician's sex, certification in family medicine or problem-based (v. traditional) medical school curriculum. CONCLUSIONS: Preventive care guidelines of the Canadian Task Force on the Periodic Health Examination have been incompletely integrated into clinical practice. Research is needed to identify and reduce barriers to the provision of preventive care and to develop and apply effective processes for the creation, dissemination and implementation of clinical practice guidelines.     

Missed opportunities for prevention in general internal medicine

BACKGROUND: According to the Canadian Society of Internal Medicine, the Canadian general internist is in the ideal position to promote patient health through disease prevention. To explore the general internist's contribution to disease prevention, the authors quantified the extent to which opportunities for prevention were addressed by the general internal medicine (GIM) service in an acute care teaching hospital in Calgary. METHODS: The authors interviewed 100 adult patients before discharge from the hospital's GIM service between May 14, 1997, and Dec. 2, 1997. The number of potential opportunities for preventive intervention were identified for each patient from 10 possible interventions recommended by the Canadian Task Force on the Periodic Health Examination (now the Canadian Task Force on Preventive Health Care): breast cancer screening, Papanicolaou smear for cervical cancer, counselling on menopausal hormone replacement therapy, digital rectal examination for prostate cancer, smoking cessation counselling, cholesterol measurement, therapy or monitoring for hypertension, influenza vaccination, pneumococcal vaccination and colorectal cancer screening. The authors determined which interventions the patient had undergone before the current admission to hospital and, using patient recall and postdischarge medical chart review, which opportunities for intervention were addressed by the GIM service during the current admission. An opportunity for preventive intervention was considered as addressed by the GIM service if it was performed during the current admission or if the general internist informed the patient or the patient's family physician of the need for such intervention in the near future. RESULTS: Among the 10 preventive interventions considered, a mean of 3.8 potential opportunities for prevention were identified for each patient. Of these, 46.5% had been addressed before the current admission, and 8.7% were addressed by the GIM service during the admission. Therefore, at the time of discharge, a mean of 55.2% of opportunities had been addressed. Among the opportunities not previously addressed, the GIM service most frequently addressed digital rectal examination for prostate cancer and cholesterol measurement. INTERPRETATION: General internists are discharging patients without sufficiently addressing opportunities for disease prevention. Preventive care protocols may be needed to limit the frequency of missed opportunities for prevention in patients admitted to tertiary care GIM services.     

Periodic health examination, 1996 update: 2. Screening for chlamydial infections. Canadian Task Force on the Periodic Health Examination.

OBJECTIVE: To update the 1984 recommendations of the Canadian Task Force on the Periodic Health Examination on the routine screening of asymptomatic patients for infection with Chlamydia trachomatis. OPTIONS: Screening, with the use of culture or nonculture tests, of the general population, of certain high-risk groups or of all pregnant women; or no routine screening. OUTCOMES: Rates of asymptomatic and symptomatic chlamydial infection, perinatal complications, longterm complications of infection (i.e., pelvic inflammatory disease, infertility and ectopic pregnancy), coinfection with other sexually transmitted diseases, disease spread, hospital care, complications of therapy and costs of infection and of screening. EVIDENCE: Search of MEDLINE for articles published between Jan. 1, 1983, and Dec. 31, 1995, with the use of the major MeSH heading "chlamydial infections," references from recent review articles and recommendation by other organizations. VALUES: The evidence-based methods of the Canadian Task Force on the Periodic Health Examination were used. Advice from reviewers and experts and recommendations of other organizations were taken into consideration. Prevention of symptomatic disease and decreased overall costs were given high values. BENEFITS, HARMS AND COSTS: The greatest potential benefits of screening asymptomatic patients for chlamydial infections are the prevention of complications, especially infertility and perinatal complications, and the prevention of disease spread. There is no evidence that screening of the general population for chlamydial infections leads to a reduction in complications, and screening may increase costs. However, there is evidence that annual screening of selected high-risk groups and of pregnant women during the first trimester is beneficial in preventing symptoms and reducing the overall cost resulting from infection. RECOMMENDATIONS: There is fair evidence to support screening and treatment of pregnant women during the first trimester (grade B recommendation) as well as annual screening and treatment of high-risk groups (sexually active women less than 25 years of age, men or women with new or multiple sexual partners during the preceding year, women who use nonbarrier contraceptive methods and women who have symptoms of chlamydial infection: cervical friability, mucopurulent cervical discharge or intermenstrual bleeding; grade B recommendation). There is fair evidence to exclude routine screening of the general population (grade D recommendation). VALIDATION: These recommendations are similar to those of the US Preventive Services Task Force and the US Centers for Disease Control and Prevention, Atlanta. SPONSOR: These guidelines were developed and endorsed by the Canadian Task Force on the Periodic Health Examination, which is funded by Health Canada and the National Health Canada and the National Health Research and Development Program. The principal author (H.D.D.) was supported in part by the Ontario Ministry of Health and the Canadian Infectious Diseases Society Lilly Fellowship.     

Preventive health care, 1999 update: 2. Echocardiography for the detection of a cardiac source of embolus in patients with stroke

OBJECTIVE: To develop guidelines for the use of echocardiography in the investigation of patients with stroke. OPTIONS: (1) Routine transthoracic echocardiography (TTE); (2) routine transesophageal echocardiography (TEE); (3) routine TTE followed by TEE if the TTE findings are noncontributory; (4) selective TTE or TEE in patients with cardiac disease who would not otherwise receive anticoagulant therapy. OUTCOMES: This article reviews the available evidence on the yield of TTE and TEE in detecting cardiac sources of cerebral emboli in patients with stroke, the effectiveness of treatment for cardiac sources of emboli and the effectiveness of screening echocardiography for secondary stroke prevention. EVIDENCE: MEDLINE was searched for relevant articles published from January 1966 to April 1998; also reviewed were additional articles identified from the bibliographies and citations obtained from experts. BENEFITS, HARMS AND COSTS: Echocardiography can detect intracardiac masses (thrombus, vegetation or tumour) in about 4% (with TTE) to 11% (with TEE) of stroke patients. The yield is lower among patients without clinical evidence of cardiac disease by history, physical examination, electrocardiography or chest radiography (less than 2%) than among patients with clinical evidence of cardiac disease (less than 19%). The risks of echocardiography to patients are small. TTE has virtually no risks, and TEE is associated with cardiac, pulmonary and bleeding complications in 0.18%. Patients with an identified intracardiac thrombus are at increased risk for embolic events (absolute risk uncertain, range 0%-38%), and this appears to be reduced with anticoagulant therapy (absolute risk reduction uncertain). Anticoagulant therapy carries a risk of major hemorrhage of 1% to 3% per year. The overall effectiveness of echocardiography in the prevention of recurrent stroke is unknown. VALUES: The strength of evidence was evaluated using the methods of the Canadian Task Force on Preventive Health Care. RECOMMENDATIONS: There is fair evidence to recommend echocardiography in patients with stroke and clinical evidence of cardiac disease by history, physical examination, electrocardiography or chest radiography (grade B recommendation). There is insufficient evidence to recommend for or against TEE in patients with normal results of TTE (grade C recommendation). There is insufficient evidence to recommend for or against routine echocardiography in patients (including young patients) without clinical cardiac disease (grade C recommendation). Routine echocardiography is not recommended for patients with clinical cardiac disease who have independent indications for or contraindications to anticoagulant therapy (grade D recommendation). There is fair evidence to recommend anticoagulant therapy in patients with stroke and intracardiac thrombus (grade B recommendation). There is insufficient (no) evidence to recommend for or against any specific therapy for patent foramen ovale (grade C recommendation). VALIDATION: The findings of this analysis were reviewed through an iterative process by the members of the Canadian Task Force on Preventive Health Care.     

Preventive health care, 1999 update: 3. Follow-up after breast cancer

OBJECTIVE: To make recommendations to physicians who provide follow-up care for women who have been treated for early-stage breast cancer. OPTIONS: Combination of blood tests, bone scans, liver echography and chest radiography for detection of distant disease; physical examination with or without mammography for detection of contralateral breast cancer; and physical examination with or without mammography for detection of ipsilateral recurrent disease after breast-conserving therapy. OUTCOMES: Survival, disease recurrence and quality-of-life measures for distant disease, local recurrence of disease and disease in the contralateral breast. EVIDENCE: A MEDLINE search for relevant articles published between January 1966 and January 1998 with the MeSH terms "breast neoplasms" and "neoplasm recurrence" (local and distant) with limits to "human" was done. A subsequent MEDLINE search using the MeSH terms "breast neoplasms," "neoplasm recurrence," "local/diagnosis" and "mammography" was done to address issues of mammography. The literature search was reviewed by a medical librarian and 2 breast cancer specialists to ensure completeness. BENEFITS, HARMS AND COSTS: Breast cancer is the most common cancer in Canadian women and is the second leading cause of death after lung cancer. Even with early-stage breast cancer, recurrence after treatment for primary breast cancer is frequent. Traditionally, follow-up has been felt to facilitate early detection and improve survival. Randomized controlled trials (RCTs) have shown that routine screening (blood tests and diagnostic imaging) for distant disease does not alter survival or quality of life over routine physical examination. In an underpowered secondary analysis of RCT data, the detection of contralateral breast cancer did not affect survival. However, there have been no RCTs examining the role of mammography and physical examination and their effect on survival in the detection of contralateral breast cancer. The sensitivity and specificity of mammography after local excision and radiotherapy is unknown. There have been no RCTs examining the role of mammography or physical examination, or both, and their effect on survival in the detection of ipsilateral breast recurrence. VALUES: The strength of evidence was evaluated using the methods of the Canadian Task Force on Preventive Health Care. A high value was placed on interventions that changed survival. When evidence was available, high value was also placed on interventions that affected quality of life. RECOMMENDATIONS: There is good evidence not to include blood work and diagnostic imaging as part of screening for distant disease (grade E recommendation). There is no evidence to suggest that mammography decreases mortality by detecting ipsilateral disease in the conservatively treated breast; however, there is indirect evidence that it may be beneficial (grade C recommendation). There is no direct evidence to suggest that physical examination or mammography, or both, should be used to detect contralateral breast cancer; however, there is indirect evidence that it may be beneficial (grade C recommendation). VALIDATION: The findings of this analysis were reviewed through an iterative process by the members of the Canadian Task Force on Preventive Health Care.     

不同剂量B族维生素对高同型半胱氨酸血症脑梗死患者的二级预防作用

目的探讨不同剂量B族维生素对高同型半胱氨酸血症（hyperho mocysteinemia,Hhcy）脑梗死患者二级预防的作用。方法采用随机对照法,将900例Hhcy脑梗死患者分为大剂量B族维生素干预组300例（口服叶酸25mg,甲钴胺500μg,维生素取30mg,均为2次／d）,小剂量B族维生素干预组300例（口服叶酸2．5mg,甲钴胺500Ixg,维生素耽30mg,均为1次／d）和对照组300例,随访1年,观察不同剂量B族维生素联合应用对脑梗死症状性复发与影像学再发的二级预防作用,记录试验期间血浆总同型半胱氨酸（total homocysteine,tHcy）水平。结果B族维生素干预可显著降低患者血浆tHcy水平,且大剂量B族维生素干预组比小剂量B族维生素干预组更明显,但对脑梗死症状性复发和影像学再发大剂量B族维生素干预组和小剂量B族维生素干预组均无明显降低。结论B族维生素可降低Hhcy脑梗死患者的血浆tHcy水平,但未能证实B族维生素干预对Hhcy脑梗死患者二级预防有益。     

Prevention. How much harm? How much benefit? 4. The ethics of informed consent for preventive screening programs.

Preventive interventions may have few or unproven benefits, or they may even be harmful. Since three of the fundamental precepts of Western biomedical ethics are beneficence, non-maleficence and respect for individual autonomy, failure to obtain truly informed consent for many current preventive interventions may be unethical. However, there are many impediments to obtaining such consent. Physicians need to be aware of an immense amount of up-to-date, complex information. It may be difficult for patients to assimilate this information, and there is rarely time for physicians to become informed and to inform their patients. Clinical practice guidelines may be helpful, but not all are based on evidence, and recommendations are often conflicting. Medical institutions, as well as individual clinicians, can help solve these dilemmas. Authors and journal editors can make a commitment to report and publish well-referenced evidence-based guidelines. Organizations such as the Canadian Task Force on the Periodic Health Examination and the US Preventive Services Task Force can develop balanced, evidence-based patient-information material. Faculty at all levels of medical education can increase their emphasis on the ethics of prevention. Individual clinicians should avoid making clinical decisions on the basis of relative reductions of morbidity or mortality, should use evidence-based clinical practice guidelines rather than those based on authority whenever possible, should make use of patient-information material and, most important, should have a consistent policy of obtaining informed consent from patients before they participate in potentially harmful preventive programs.     

Periodic health examination, 1994 update: 1. Obesity in childhood. Canadian Task Force on the Periodic Health Examination.

OBJECTIVE: To update the 1979 Canadian Task Force on the Periodic Health Examination recommendation on screening for childhood obesity by reviewing any new evidence concerning health risks in childhood and adulthood, and effective preventive or therapeutic interventions. OPTIONS: Detection: routine measurement of height and weight, use of skinfold thickness measurements, calculation of body mass index (BMI). Intervention: diet, exercise, behaviour modification and comprehensive family-based weight-reduction programs. Components of these interventions could be offered routinely or reserved for children and families who perceive obesity to be a present or potential problem. OUTCOMES: The task force reviewed the probability of obese children become obese adults as a risk factor for adult heart disease and overall related illness and death in adult life as well as obesity as a risk factor for physical and psychologic illness in childhood. EVIDENCE: A MEDLINE search for relevant articles published between January 1981 and February 1991 was undertaken. VALUES: The task force's evidence-based rules for recommendations were used. BENEFITS, HARMS AND COSTS: If weight reduction in childhood were shown to prevent physical or psychologic illness in childhood, or illness and death in adult life, screening and treatment should be recommended. Screening for obesity may cause anxiety on the part of the child and family; malnutrition in children as a result of parents becoming overly anxious about the health risks of obesity has been reported. Most weight reduction programs have limited long-term effectiveness and can be costly. RECOMMENDATIONS: There is insufficient evidence of short-term or long-term benefits from screening for or treatment of childhood obesity to recommend such screening or recommend against it. There is fair evidence to recommend against very-low-kilojoule diets for preadolescents. There is insufficient evidence to recommend for or against exercise programs or intensive family-based programs for most obese children. VALIDATION: These recommendations are similar to those of the American Academy of Pediatrics and the US Preventive Services Task Force. SPONSOR: These guidelines were developed and endorsed by the Canadian task force, which is funded by Health Canada.     

Periodic health examination, 1995 update: 3. Screening for visual problems among elderly patients. Canadian Task Force on the Periodic Health Examination.

OBJECTIVE: To provide recommendations to family physicians for screening elderly patients (over 65 years of age) for visual impairment and its common clinical causes. OPTIONS: Visual acuity screening with Snellen sight chart, funduscopy, retinal photography, tonometry and perimetry. OUTCOMES: Delay or prevention of visual deterioration or blindness. EVIDENCE: A MEDLINE search for relevant articles published between January 1986 and December 1993 was undertaken, the bibliographies of the articles were scrutinized for additional articles, and experts were consulted. The highest available level of evidence was used in making recommendations. VALUES: The evidence-based methods and values of the Canadian Task Force on the Periodic Health Examination were used. Preservation of vision was given the highest value in accordance with other guidelines regarding eyesight. BENEFITS, HARMS AND COSTS: Potential benefits are to maintain or improve visual acuity. Potential for harm to patients is minimal. Limited data are available on costs. RECOMMENDATIONS: There is fair evidence to include in the periodic health examination visual acuity testing with a Snellen sight chart and funduscopy or retinal photography in elderly patients with diabetes of at least 5 years' duration (grade B recommendation). The place of funduscopy in the detection of age-related macular degeneration and glaucomatous changes is controversial. For patients at high risk for glaucoma (positive family history, black race, severe myopia or diabetes) it would be prudent to have a periodic assessment by an ophthalmologist. VALIDATION: Recommendations differ from those of the American Academy of Ophthalmology and the American Optometric Association. Recommendations for glaucoma screening are similar to those of the US Preventive Services Task Force. Present recommendations have been reviewed by experts in ophthalmology and optometry. SPONSOR: These guidelines were developed and endorsed by the task force, which is funded by Health Canada and the National Health Research and Development Program. The principal author (C.P.) was supported in part by the Educational Centre for Aging and Health, McMaster University, Hamilton, Ont.     

Vitamin supplementation of patients receiving haemodialysis

In order to assess the necessity of vitamin supplementation for patients who are receiving haemodialysis, measurements of vitamin status were made, and both dietary and supplementary intakes were assessed, in 26 patients who were undergoing haemodialysis. Blood samples were collected from these patients before they underwent haemodialysis, after an overnight fast, for the measurement of plasma retinol, alpha-tocopherol and ascorbate levels. Serum and erythrocyte folate levels were measured also. Thiamin status was assessed by the effect of added thiamin pyrophosphate on erythrocyte transketolase activity and pyridoxine status was assessed by the effect of added pyridoxal-5'-phosphate on erythrocyte aminotransferase activity. All patients had elevated plasma retinol levels; 48% of patients had elevated plasma alpha-tocopherol levels; the plasma ascorbate level was low in 50% of patients but was elevated in 25% of patients; and plasma and erythrocyte folate levels were elevated in 76% and 91% of patients, respectively. Thiamin status was normal in all but one patient and the pyridoxine level appeared to be low in two other patients. Many patients had low dietary intakes of vitamin C, folate and vitamin B6. We conclude that supplements of vitamins A and E are not required and, when dietary intakes of water-soluble vitamins are marginal, these should be supplemented at a dose as near as possible to the recommended dietary intake.     

维生素对大鼠脂质及脂质过氧化作用的影响

目的　探讨不同种类维生素对大鼠血浆胆固醇及脂质过氧化作用的影响。方法　各组大鼠均灌胃给予胆固醇乳化剂 ,并在饮水中加入 0 .5 %的蛋氨酸 ,同时各实验组分别给予相应维生素 ,对照组给予等量的生理盐水 ,连续 4周。用酶法和TBA荧光测定法分别检测血清胆固醇和脂过氧化物的水平。结果　维生素E、C、B6、B12 及叶酸单用或联用均能显著降低血清脂过氧化物的水平 ,其中维生素C、B6、B12 +叶酸还有降低血清胆固醇的作用。结论　维生素的适当补充对消除动脉粥样硬化的危险因素有一定的作用     

B族维生素治疗肾移植受者高同型半胱氨酸血症

目的：探讨叶酸、维生素B6及B12在治疗肾移植患者高同型半胱氨酸（Hcy）血症中的作用。方法：将195例预接受首次肾移植患者随机分为两组：试验组103例,口服叶酸5mg/d,维生素B6 50mg/d及维生素B12 1mg/d,连续2个月左右;对照组92例则未口服B族维生素。分别于服药治疗前、术前1d、术后1、10、20及30d检测血浆Hcy浓度和血清肌酐水平。结果：试验组血浆Hcy浓度与对照组相比具有统计学意义（P＜0.0001）,试验组术后血清肌酐水平下降较快,发生急性排斥反应的比例低于对照组。结论：肾移植患者围手术期适当补充叶酸、维生素B6及B12可降低血浆Hcy浓度,有助于移植肾功能的快速恢复,是减少肾移植并发症及急性排斥反应的重要措施。     

冠心病患者血浆同型半胱氨酸水平与血清叶酸、维生素B12浓度的相关性研究

目的观察高同型半胱氨酸血症（HHCY）是否是人群发生冠心病（CHD）的独立危险因素，同时探讨CHD患者血中同型半胱氨酸（HCY）、叶酸、VitB12浓度的变化及其相关性。方法选择CHD患者123例，正常对照101例。采用荧光偏振免疫分析法测定血浆HCY水平，化学发光免疫分析法测定血清叶酸、VitB12浓度。结果（1）CHD组患者血浆HCY平均浓度（15．04±7．58）μmol／L显著高于正常对照组（10．08±3．11）μmol／L，P〈0．01，CHD组患者血清叶酸平均浓度（4．02±2．27）ng/ml显著低于对照组（5．93±2．76）ng／ml，P〈0．01，CHD组患者血清VitBt2平均浓度（303．63±130．51）pg／ml与正常对照组（292．17±94．05）pg/ml比较差异无显著性（P〉0．05）。CHD组HHCY的发生率（36．59％）亦明显高于对照组（9．90％，P〈0．01）。CHD病因的多元Logistic回归分析显示HCY是CHD发病的独立危险因素。HCY对于CHD的相对危险度（RR）为1．238。相关分析显示：CHD组血浆HCY水平与血清叶酸、与VitB12浓度呈显著负相关（P=0．000）。结论HHCY是CHD的独立危险因素。CHD组血浆HCY水平与血清叶酸、与VitB12浓度呈线性负相关。血浆HCY、叶酸浓度检测有助CHD的诊断。     

老年人群营养状况调查分析

目的 :探讨老年人的膳食及营养状况。方法 :选择 97名 60～ 69岁男性为调查对象 ;膳食调查采用 4天称量法 ;尿负荷试验 ,试验者于清晨空腹时口服维生素 B1、B2 各 5mg及维生素 C 50 0 mg,收集 4 h尿 ,用 2 ,4 -二硝基苯肼比色法测定尿中维生素 C含量 ;用荧光光度法测定尿中维生素 B1、B2 含量。结果 :维生素 A和钙的摄入量分别占供给量 2 1.5%和 52 .7% ,热能和其他营养素摄入量均超过或达到我国推荐的营养素供给量标准。结论 :老年人从膳食中摄入的热能和大多数营养素均达到了供给量标准     

冠心病患者血清同型半胱氨酸与叶酸、维生素B12水平的变化

目的 探讨冠心病患者血清同型半胱氨酸(HCY)与叶酸、维生素B12浓度的变化及其相关性。方法 选择84例经冠状动脉造影术证实为冠心病的患者，应用荧光偏振免疫分析法(FPIA)测定血清HCY浓度，离子捕获免疫分析法(ICIA)测定血清叶酸浓度，非均相微粒子酶免疫分析法（MEIA)测定血清维生素B12浓度。结果 冠心病患者血清HCY浓度增高，与正常对照组比较有显著性意义(P＜0．001)，而叶酸、维生素B12浓度则降低，与正常对照组比较有显著性意义(P＜0．001)，以上两种变化呈负相关(P＜0．001)。结论 同型半胱氨酸血症是冠心病的新的独立危险因素，叶酸、维生素B12缺乏可能是诱发高HCY的重要因素。     

Periodic health examination, 1996 update: 1. Prenatal screening for and diagnosis of Down syndrome. Canadian Task Force on the Periodic Health Examination.

OBJECTIVE: To make recommendations to physicians providing prenatal care on (1) whether prenatal screening for and diagnosis of Down syndrome (DS) is advisable and (2) alternative screening and diagnosis manoeuvres. OPTIONS: "Triple-marker" screening of maternal serum levels of alpha-fetoprotein, human chorionic gonadotropin and unconjugated estriol; fetal ultrasonographic examination; amniocentesis; and chorionic villus sampling (CVS). OUTCOMES: Accuracy of detection of DS in fetuses, and risks to the mother, including psychologic distress, and to the fetus from the screening and diagnostic interventions. EVIDENCE: A MEDLINE search for relevant articles published from Jan. 1, 1966, to Mar. 31, 1994, with the use of MeSH terms "Down syndrome," "prenatal diagnosis," "screening," "prevention," "amniocentesis," "chorionic villus sampling," "ultrasonography," "anxiety," "depression" and "psychological stress" and a manual search of bibliographies, recent issues of key journals and Current Contents. VALUES: The evidence-based methods and values of the Canadian Task Force on the Periodic Health Examination were used. A high value was placed on providing pregnant women with the opportunity to determine whether they are carrying a fetus with DS and to make choices concerning the termination of the pregnancy. The economic issues involved are complex and were not considered. BENEFITS, HARMS AND COSTS: Triple-marker screening identifies an estimated 58% of fetuses with DS, but it has an estimated rate of true-positive results of 0.1% and of false-positive results of 3.7% (given a risk cut-off of one chance in 190 of DS). These rates vary with maternal age and the risk cut-off chosen. Women with a known risk of having a fetus with DS (e.g., those who have had a previous child with DS) may benefit from a reduction in anxiety after confirmation that their fetus does not have DS. Screening allows women at low risk of having a child with DS to detect fetuses with the syndrome, but may cause psychologic distress if there is a false-positive screening test result. Up to 20% of women with positive results of screening tests may decline to undergo a subsequent amniocentesis. Amniocentesis and CVS are very accurate in diagnosing DS in fetuses and have a very low rate of serious complications for the mother. Amniocentesis is associated with a 1.7% rate of fetal loss when it is performed after 16 weeks' gestation, whereas the rate among controls is 0.7% (for a difference of 1%, 95% confidence interval 0.3% to 1.5%). CVS entails a greater risk of fetal loss than amniocentesis (odds ratio 1.32, 95% confidence interval 1.11 to 1.57). There is little evidence from controlled trials of significant associations between amniocentesis or CVS and neonatal morbidity or malformations; however, samples have been too small to show differences in rare outcomes. Results from some case-control studies suggest that CVS increases the risk of transverse limb deficiency. Costs were not considered because they are beyond the scope of this review. RECOMMENDATIONS: There is fair evidence to offer triple-marker screening through a comprehensive program to pregnant women under 35 years of age (grade B recommendation). Women given detailed information about serum-marker screening show more satisfaction with the screening than those not given this information. There is fair evidence to offer amniocentesis or CVS to pregnant women 35 years of age and older and to women with a history of a fetus with DS or of a chromosome 21 anomaly (grade B recommendation). Information on the limitations and advantages of each procedure should be offered. Triple-marker screening may be offered as an alternative to CVS or amniocentesis to pregnant women over 35. VALIDATION: Recommendations concerning prenatal diagnosis are similar to those of the US Preventive Services Task Force, the Society of Obstetricians and Gynaecologists of Canada, the Canadian College of Medical Geneticists and the Cochrane Pregnancy and Childbirth Group. No previous specific recommendations concerning triple-maker screening exist. SPONSORS: These guidelines were developed and endorsed by the Canadian Task Force on the Periodic Health Examination, which is funded by Health Canada and the National Health Research and Development Program.     

Periodic health examination, 1995 update: 2. Prevention of dental caries. The Canadian Task Force on the Periodic Health Examination.

OBJECTIVE: To make recommendations, based on current evidence, for practising physicians and dentists on interventions for the prevention of dental caries in their patients. OPTIONS: Systemic fluoride administration, professionally administered fluoride, use of fluoride mouth rinses, fissure sealants, oral-hygiene practices, dietary practices, identification of groups at a high risk of dental caries, and early diagnosis and treatment. OUTCOMES: Reduced prevalence of dental caries and fluorosis, longer retention of teeth and lower treatment costs. EVIDENCE: Several MEDLINE searches were conducted for articles published from January 1980 to December 1992, including relevant review articles. VALUES: Relevant clinical findings were evaluated and categorized with the use of the evidence-based methods and values of the Canadian Task Force on the Periodic Health Examination. Recommendations were developed for each method of caries prevention, with reduced incidence of dental caries and improved prevalence of caries-free teeth given high values. BENEFITS, HARMS AND COSTS: The potential benefits of these measures in the long-term are a lower incidence of tooth decay, longer retention of teeth and prevention of fluorosis. The cost saving can be considerable for patients and insurers; however, implementation of some recommendations will be difficult, since the traditional preventive practices of dentists and dental hygienists are not easily changed. RECOMMENDATIONS: There is good evidence that the following manoeuvres are effective in preventing dental caries: use of dentifrices containing fluoride, fluoridation of drinking water, fluoride supplements for patients in areas where there is a low level (0.3 ppm or less) of fluoride in the drinking water, professionally applied topical fluoride and the use of fluoride mouth rinses for patients with very active decay or at a high risk of dental caries and selective use of professionally applied fissure sealants on permanent molar teeth. There is poor evidence that the following manoeuvres are effective in preventing dental caries: professionally applied topical fluoride and the use of fluoride mouth rinses for patients with a low risk of caries, toothbrushing (without a dentifrice containing fluoride) and flossing, cleaning of teeth by a dentist or dental hygienist before topical application of fluoride or at a dental visit and dietary counselling for the general population. There is good evidence to recommend against the use of over-the-counter fluoride mouth rinses by the general population. VALIDATION: These guidelines are compatible with those of the US Preventive Services Task Force. SPONSOR: These guidelines were developed and endorsed by the task force, which is funded by Health Canada. Major funding was provided by the Faculty of Dentistry of the University of Toronto, Toronto and the Faculty of Dentistry of Dalhousie University, Halifax.     

Clinical usefulness of plasma homocysteine in vascular disease

Raised plasma homocysteine (tHcy) concentrations are caused by genetic mutations, vitamin deficiencies, renal and other diseases, numerous drugs, and increasing age. Raised tHcy concentrations are associated with laboratory evidence of atherogenesis (eg, endothelial dysfunction) and thrombosis, and epidemiological evidence of an increased risk of atherothrombotic vascular disease. An association between raised tHcy concentration and an increased risk of atherothrombosis is independent of other vascular risk factors, strong, dose-related and biologically plausible, but has not been proven to be causal in randomised controlled trials. A recent trial identified no significant benefit from lowering tHcy concentration by folic-acid-based multivitamin therapy among 3680 patients with recent ischaemic stroke, but did not reliably exclude a modest but important reduction in the relative risk of stroke of up to 20%; a difference of only 2 mmol/L in tHcy concentration between the two treatment groups was probably due to widespread vitamin use and fortification of grains and staple foods with folate in North America. There is currently insufficient evidence to recommend routine screening and treatment of high tHcy concentrations with folic acid and other vitamins to prevent atherothrombotic vascular disease.