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文献质量评估
各纳入RCT的方法学质量评价采用Cochrane5.1手册推荐的简单评估法［9］，评价的关键指标:①随机方法是否正确；②是否做到分配隐藏，分配方法是否正确；③是否实施盲法；
④是否报告失访和退出情况；⑤基线是否可比。
对于分配隐藏，将试验评为A（完全隐藏）、B（不清楚是否隐藏）、C（隐藏不充分）和D（没有使用隐藏）4个等级。
在其他方面将试验评为A（是）、B（不清楚）、C（否）三级。
如各评价条目均为A级，则为低度偏倚，发生各种偏倚的可能性最小，质量评为A级；若有一条目或多个条目为B，则该试验有发生相应偏倚的中等度可能性，质量评为B级；如其中有一条目或多个条目为C，则该试验有发生相应偏倚的高度可能性，质量评为C级。
中文：Table 8.5.a: The Cochrane Collaboration’s tool for assessing risk of biasTable 8.5.d: Criteria for judging risk of bias in the ‘Risk of bias’ assessment tool研究者描述随机序列产生过程譬如:参考随机数字表使用计算机随机数字生成器扔硬币洗牌的卡片和信封掷骰子抽签最小化*最小化，可实现无随机元素，被认为相当于是随机的。
研究者描述序列的产生使用的是非随机的方法。
通常是系统的非随机方法，例如：通过奇偶或出生日期产生序列通过入院日期产生序列通过类似住院号或门诊号产生序列相对于上面提到的系统方法，其它非随机的方法少见的多，也更明显。
通常包括对参与者进行判断或非随机的方法，例如:临床医生判断如何分配参与者判断如何分配基于实验室检查或系列测试的结果分配基于干预的可获取性进行分配中心分配（包括电话，网络，药房控制随机）相同外形的顺序编号的药物容器；顺序编号、不透明、密封的信封参与者以及纳入参与者的研究者可能事先知道分配，因而引入选择偏倚，譬如基于如下方法的分配:使用摊开的随机分配表（如随机序列清单）分发信封但没有合适的安全保障（如透明、非密封、非顺序编号）交替或循环出生日期病历号其它明确的非隐藏过程任何如下标准:无盲法或盲法不充分，但系统评价员判断结局不太可能受到缺乏盲法的影响参与者和主要实施者均实施可靠的盲法，且盲法不太可能被打破任何如下标准:无盲法或盲法不充分，但系统评价员判断结局很可能受到缺乏盲法的影响尝试对关键的参与者和实施者行盲法，但盲法很可能被打破，结局很可能受到缺乏盲法的影响任何如下标准:没有足够信息判断为低风险或高风险研究未描述此情况任何如下标准:无盲法或盲法不充分，但系统评价员判断结局不太可能受到缺乏盲法的影响参与者和主要实施者均实施可靠的盲法，且盲法不太可能被打破任何如下标准:无盲法或盲法不充分，但系统评价员判断结局很可能受到缺乏盲法的影响尝试对关键的参与者和实施者行盲法，但盲法很可能被打破，结局很可能受到缺乏盲法的影响任何如下标准:没有足够信息判断为低风险或高风险研究未描述此情况任何如下标准:无缺失数据缺失数据的产生不大可能与真实结局相关（对于生存数据，删失不大可能引入偏倚）缺失数据的数目在各干预组相当，且各组缺失原因类似对二分类变量，与观察事件的发生风险相比，缺失比例不足以影响预估的干预效应对连续性结局数据，缺失数据的合理效应规模（均数差或标准均数差）不会大到影响观察的效应规模;缺失的数据用合适的方法进行估算任何如下标准:缺失数据的产生很大可能与真实结局相关, 缺失数据的数目及缺失原因在各干预组相差较大对二分类变量，与观察事件的发生风险相比，缺失比例足以影响预估的干预效应对连续性结局数据，缺失数据的合理效应规模（均数差或标准均数差）足以影响观察的效应规模;意向治疗分析中存在实际干预措施与随机分配的干预相违背的情况对缺失数据进行简单的不合适的估算任何如下标准:没有报道缺失或排除的情况，无法判断高风险或低风险（如未说明随机的数量，未提供数据缺失的原因）研究未描述此情况任何如下标准:实验的计划书可获取，系统评价感兴趣的所有首要或次要结局均按计划书预先说明的方式报道实验计划书不可得，但很明显发表的报告包括所有的结局，包括预先说明的结局（这种性质的有说服力的文字可能少见）任何如下标准:不是所有的预先说明的首要结局均被报道一个或多个首要结局为采用预先说明的测量方法、分析方法或数据子集来报道系统评价感兴趣的一个或多个首要结局报道不全，以至于不能纳入meta分析研究未报道此研究应当包含的主要关键结局具有与特殊试验设计相关的潜在偏倚来源或被指欺诈或其它问题可能存在偏倚风险，但存在以下两种中的一种没有足够信息评估是否存在其它重要的偏倚风险没有足够的证据认为发现的问题会引入偏倚Table 8.7.a: Possible approach for summary assessments of the risk of bias for each important outcome (across domains) within and across studies英文：Table 8.5.a: The Cochrane Collaboration’s tool for assessing risk of biasTable 8.5.d: Criteria for judging risk of bias in the ‘Risk of bias’ assessment toolprocess such as:Referring to a random number table;Using a computer random number generator;Coin tossing;Shuffling cards or envelopes;Throwing dice;Drawing of lots;Minimization*.*Minimization may be implemented without a random element, and this isconsidered to be equivalent to being random.judgement The investigators describe a non-random component in the sequence generation process. Usually, the description would involve somesystematic, non-random approach, for example:Sequence generated by odd or even date of birth;Sequence generated by some rule based on date (or day) of admission;Sequence generated by some rule based on hospital or clinic recordnumber.Other non-random approaches happen much less frequently than thesystematic approaches mentioned above and tend to be obvious. Theyusually involve judgement or some method of non-random categorization ofparticipants, for example:Allocation by judgement of the clinician;Allocation by preference of the participant;Allocation based on the results of a laboratory test or a seriesof tests;Allocation by availability of the intervention.Criteria for a judgement Participants and investigators enrolling participants could not foreseeassignment because one of the following, or an equivalent method, was usedto conceal allocation:Central allocation (including telephone, web-based andpharmacy-controlled randomization);Sequentially numbered drug containers of identical appearance;Sequentially numbered, opaque, sealed envelopes.judgement Participants or investigators enrolling participants could possiblyforesee assignments and thus introduce selection bias, such as allocationbased on:Using an open random allocation schedule (e.g. a list of randomnumbers);Assignment envelopes were used without appropriate safeguards(e.g. if envelopes were unsealed or nonopaque or not sequentiallynumbered);Alternation or rotation;Date of birth;Case record number;Any other explicitly unconcealed procedure.Criteria for a judgement Any one of the following:No blinding or incomplete blinding, but the review authors judgethat the outcome is not likely to be influenced by lack of blinding;Blinding of participants and key study personnel ensured, andunlikely that the blinding could have been broken.judgementAny one of the following:No blinding or incomplete blinding, and the outcome is likely tobe influenced by lack of blinding;Blinding of key study participants and personnel attempted, butlikely that the blinding could have been broken, and the outcomeis likely to be influenced by lack of blinding.judgement ‘Unclear risk’ ofAny one of the following:Insufficient information to permit judgement of ‘Low risk’ or ‘High risk’;The study did not address this outcome.Criteria for a judgement Any one of the following:No blinding of outcome assessment, but the review authors judge thatthe outcome measurement is not likely to be influenced by lack ofblinding;Blinding of outcome assessment ensured, and unlikely that theblinding could have been broken.judgementAny one of the following:No blinding of outcome assessment, and the outcome measurement islikely to be influenced by lack of blinding;Blinding of outcome assessment, but likely that the blinding couldhave been broken, and the outcome measurement is likely to beinfluenced by lack of blinding.judgement ‘Unclear risk’ ofAny one of the following:Insufficient information to permit judgement of ‘Low risk’ or‘High risk’;The study did not address this outcome.Criteria for a judgement Any one of the following:No missing outcome data;Reasons for missing outcome data unlikely to be related to trueoutcome (for survival data, censoring unlikely to be introducingbias);Missing outcome data balanced in numbers across interventiongroups, with similar reasons for missing data across groups;For dichotomous outcome data, the proportion of missing outcomescompared with observed event risk not enough to have a clinicallyrelevant impact on the intervention effect estimate;For continuous outcome data, plausible effect size (difference inmeans or standardized difference in means) among missing outcomesnot enough to have a clinically relevant impact on observed effectsize;Missing data have been imputed using appropriate methods.judgement Any one of the following:Reason for missing outcome data likely to be related to trueoutcome, with either imbalance in numbers or reasons for missingdata across intervention groups;For dichotomous outcome data, the proportion of missing outcomescompared with observed event risk enough to induce clinicallyrelevant bias in intervention effect estimate;For continuous outcome data, plausible effect size (difference inmeans or standardized difference in means) among missing outcomesenough to induce clinically relevant bias in observed effect size;‘As-treated’ analysis done with substantial departure of theintervention received from that assigned at randomization;Potentially inappropriate application of simple imputation.judgement ‘Unclear risk’ ofAny one of the following:Insufficient reporting of attrition/exclusions to permit judgement of ‘Low risk’ or ‘High risk’ (e.g. number ran domized not stated,no reasons for missing data provided);The study did not address this outcome.Criteria for a judgement Any of the following:The study p rotocol is available and all of the study’spre-specified (primary and secondary) outcomes that are of interestin the review have been reported in the pre-specified way;The study protocol is not available but it is clear that thepublished reports include all expected outcomes, including thosethat were pre-specified (convincing text of this nature may beuncommon).judgementAny one of the following:Not all of the study’s pre -specified primary outcomes have beenreported;One or more primary outcomes is reported using measurements,analysis methods or subsets of the data (e.g. subscales) that werenot pre-specified;One or more reported primary outcomes were not pre-specified(unless clear justification for their reporting is provided, suchas an unexpected adverse effect);One or more outcomes of interest in the review are reportedincompletely so that they cannot be entered in a meta-analysis;The study report fails to include results for a key outcome thatwould be expected to have been reported for such a study.judgementThere is at least one important risk of bias. For example, the study: Had a potential source of bias related to the specific study designused; orHas been claimed to have been fraudulent; orHad some other problem.judgement ‘Unclear risk’ ofThere may be a risk of bias, but there is either:Insufficient information to assess whether an important risk of bias exists; orInsufficient rationale or evidence that an identified problem willintroduce bias.Table 8.7.a: Possible approach for summary assessments of the risk of bias for each important outcome (across domains) within and across studies。
judgement of ‘Low The investigators describe a random component in the sequence generation process such as:Referring to a random number table;Using a computer random number generator;Coin tossing;Shuffling cards or envelopes;Throwing dice;Drawing of lots;Minimization*.‘High The investigators describe a non-random component in the sequence generation process. Usually, the description would involve some systematic, non-random approach, for example: Sequence generated by odd or even date of birth;Sequence generated by some rule based on date (or day)of admission;Sequence generated by some rule based on hospital orclinic record number.Other non-random approaches happen much less frequently than the systematic approaches mentioned above and tend to be obvious.? They usually involve judgement or some method of non-random categorization of participants, for example: Allocation by judgement of the clinician;Allocation by preference of the participant;Allocation based on the results of a laboratory test ora series of tests;Allocation by availability of the intervention.Participants and investigators enrolling participants could not foresee assignment because one of the following, or an equivalent method, was used to conceal allocation: Central allocation (including telephone, web-based andpharmacy-controlled randomization);Sequentially numbered drug containers of identicalappearance;Sequentially numbered, opaque, sealed envelopes.‘High Participants or investigators enrolling participants could possibly foresee assignments and thus introduce selection bias, such as allocation based on:Using an open random allocation schedule (e.g. a listof random numbers);Assignment envelopes were used without appropriatesafeguards (e.g. if envelopes were unsealed or non-opaque or not sequentially numbered);Alternation or rotation;Date of birth;Case record number;Any other explicitly unconcealed procedure.Any one of the following:judgement of ‘LowNo blinding or incomplete blinding, but the reviewauthors judge that the outcome is not likely to beinfluenced by lack of blinding;Blinding of participants and key study personnelensured, and unlikely that the blinding could have beenbroken.Any one of the following:‘HighNo blinding or incomplete blinding, and the outcome islikely to be influenced by lack of blinding;Blinding of key study participants and personnelattempted, but likely that the blinding could have beenbroken, and the outcome is likely to be influenced bylack of blinding.Any one of the following:Insufficient information to permit judgement of ‘Lowrisk’ or ‘High risk’;The study did not address this outcome.Any one of the following:judgement of ‘LowNo blinding of outcome assessment, but the reviewauthors judge that the outcome measurement is not likelyto be influenced by lack of blinding;Blinding of outcome assessment ensured, and unlikelythat the blinding could have been broken.Any one of the following:‘HighNo blinding of outcome assessment, and the outcomemeasurement is likely to be influenced by lack ofblinding;Blinding of outcome assessment, but likely that theblinding could have been broken, and the outcomemeasurement is likely to be influenced by lack ofblinding.Any one of the following:Insufficient information to permit judgement of ‘Lowrisk’ or ‘High risk’;The study did not address this outcome.Any one of the following:judgement of ‘LowNo missing outcome data;Reasons for missing outcome data unlikely to be relatedto true outcome (for survival data, censoring unlikelyto be introducing bias);Missing outcome data balanced in numbers acrossintervention groups, with similar reasons for missingdata across groups;For dichotomous outcome data, the proportion of missingoutcomes compared with observed event risk not enoughto have a clinically relevant impact on the interventioneffect estimate;For continuous outcome data, plausible effect size(difference in means or standardized difference inmeans) among missing outcomes not enough to have aclinically relevant impact on observed effect size;Missing data have been imputed using appropriatemethods.Any one of the following:‘HighReason for missing outcome data likely to be related totrue outcome, with either imbalance in numbers orreasons for missing data across intervention groups;For dichotomous outcome data, the proportion of missingoutcomes compared with observed event risk enough toinduce clinically relevant bias in intervention effectestimate;For continuous outcome data, plausible effect size(difference in means or standardized difference inmeans) among missing outcomes enough to induceclinically relevant bias in observed effect size;‘As-treated’ analysis done with substantialdeparture of the intervention received from thatassigned at randomization;Potentially inappropriate application of simpleimputation.Any one of the following:Insufficient reporting of attrition/exclusions topermit judgement of ‘Low risk’ or ‘High risk’ (e.g.number randomized not stated, no reasons for missingdata provided);The study did not address this outcome.Any of the following:judgement of ‘LowThe study protocol is available and all of the study’spre-specified (primary and secondary) outcomes that areof interest in the review have been reported in thepre-specified way;The study protocol is not available but it is clear thatthe published reports include all expected outcomes,including those that were pre-specified (convincingtext of this nature may be uncommon).Any one of the following:‘HighNot all of the study’s pre-specified primary outcomeshave been reported;One or more primary outcomes is reported usingmeasurements, analysis methods or subsets of the data (e.g. subscales) that were not pre-specified;One or more reported primary outcomes were notpre-specified (unless clear justification for their reporting is provided, such as an unexpected adverse effect);One or more outcomes of interest in the review are reported incompletely so that they cannot be entered in a meta-analysis;The study report fails to include results for a key outcome that would be expected to have been reported for such a study.Had a potential source of bias related to the specificstudy design used; orHas been claimed to have been fraudulent; orHad some other problem.There may be a risk of bias, but there is either: Insufficient information to assess whether an importantrisk of bias exists; orInsufficient rationale or evidence that an identifiedproblem will introduce bias.。
rct文献质量评价表
rct（随机对照试验）文献质量评价表通常包括以下几
个方面的评价内容：
1.随机方法：评价随机方法是否正确，是否能够保证试验组和对照组的基线一致性。
2.对照设置：评价对照组的设置是否合理，是否能够反映实际临床情况，以及对照组是否与试验组具有可比性。
3.盲法实施：评价试验实施过程中是否采用盲法，是否能够减少主观偏倚的影响。
4.样本量：评价样本量是否足够大，以确保结果的稳定性和可靠性。
5.数据完整性：评价数据是否完整，是否有缺失或异常值，以及是否进行了合理的处理。
6.基线情况：评价试验组和对照组的基线情况是否相似，以确保试验结果的公正性和客观性。
7.疗效评价：评价疗效评价标准是否科学、客观、可重复，以及是否进行了合理的统计学分析。
8.安全性评价：评价安全性评价方法是否科学、客观、可重复，以及是否进行了合理的统计学分析。
9.试验流程：评价试验流程是否规范、合理，以及是否符合伦理要求。
10.结论可靠性：综合以上各点，对试验结论的可靠性进行评价。
在具体应用中，可以根据实际情况对rct文献质量评价表进行适当调整和增删。
cochrane文献评价手册
（原创实用版）
目录
1.Cochrane 文献评价手册的概述
2.手册的目的和适用范围
3.手册的主要内容
4.手册的评价标准和方法
5.手册的实际应用和影响
正文
Cochrane 文献评价手册是由 Cochrane 协作组织编写的一本关于如何评价和分析医学研究文献的手册。
Cochrane 协作组织是一个国际性的非营利组织，致力于通过系统评价和荟萃分析的方法，为医疗决策提供高质量的证据。
手册的目的是为了帮助 Cochrane 协作组织的成员和其它医学研究者，更好地评价和分析医学研究文献，以提供更准确、更全面、更可信的医学证据。
适用范围主要是针对 Cochrane 系统评价和荟萃分析的研究项目，也适用于其它类型的医学研究。
手册的主要内容包括：如何选择研究文献，如何提取和分析研究数据，如何评价研究的质量，如何解决研究中的偏倚和误差，以及如何撰写系统评价和荟萃分析报告等。
手册的评价标准和方法主要是根据 Cochrane 协作组织的标准和方法，结合循证医学和统计学的原理，对研究文献的质量、数据的可靠性、研究的有效性等进行评价和分析。
手册的实际应用和影响非常广泛。
它不仅被 Cochrane 协作组织的成员广泛使用，也被其它医学研究者和医疗机构所接受和应用。
cochrane文献质量评价分级医学文献的定义及类别“文献”一词出现在中国已有2000多年的历史，从春秋战国时期就有关于文献的记载，最早见于《论语八佾》。
随着人类文明的发展，“文献”的概念也发生了巨大的变化，人们对文献的研究一直持续至今。
文献的具体定义尚缺乏统一的定论，《现代汉语词典》对文献的定义是“有历史价值或参考价值的资料”［1］;《中华人民共和国国家标准—文献著录总则》将文献定义为“记载有知识的一切载体”［2］。
有学者将文献定义为“文献就是将知识、信息用文字、符号、图像、音频等记录在一定物质载体上的结合体”［3］。
有历史价值和研究价值的知识、一定的载体、一定的方法和手段、一定的意义表达和记录体系这4个方面构成文献的基本要素。
医学文献(medicalliterature)就是与医学有关的有参考价值的资料。
按照文献的研究类型分为:系统评价、随机对照临床试验、队列研究、病例对照研究、病例系列研究、病例报告和专家经验总结等。
决定文献质量的关键部分:研究有首创性或提供了新证据、研究对象的选择合理、科研设计合理、偏倚得到有效控制、研究样本量足够大和研究的时间足够长。
然而医学文献是如何发挥作用的，前提就是该文献必须有一定的价值，而且有可靠的等级评价体系。
医学文献的价值就是根据其文献内在及外在真实性及临床意义的重要性去评判，是根据医学研究的方向不同确定评价的原则和方法［4］，其中内在真实性是文献评价的重点。
2西医文献评价体系2.1证据分级20世纪60年代，首次提出证据分级概念，将随机对照研究的质量定为最高，并引入内部真实性和外部真实性的概念。
证据分级为西医识别文献可靠性的准则。
最初3级标准:1级:设计良好的随机对照试验(RCT);2级:1级和3级中间的类型;3级:专家经验。
老5级标准:1级:收集所有质量可靠的RCT后做出的系统评价或Meta分析结果，大样本多中心随机对照试验;2级:单个大样本的RCT结果;3级:设有对照但未用随机方法分组的研究病例对照研究和队列研究;4级:无对照的系列病例观察;5级:专家意见、描述性研究和病例报告。
cochrane文献评价手册【原创实用版】目录1.Cochrane 文献评价手册的概述2.手册的目的和适用范围3.手册的主要内容4.手册的评价标准和方法5.手册的优点和不足6.对我国相关领域的影响和启示正文1.Cochrane 文献评价手册的概述Cochrane 文献评价手册是由 Cochrane 协作组织编写的一本关于如何评价和分析医学文献的指南。
Cochrane 协作组织是一个国际性的、非营利的医学研究组织，致力于通过系统评价和荟萃分析的方法，为临床决策提供高质量的证据。
2.手册的目的和适用范围本手册的主要目的是为系统评价和荟萃分析提供一种标准和方法，以便为临床决策提供可靠的证据。
它适用于所有从事医学研究、临床实践和卫生政策制定的人员。
3.手册的主要内容手册主要包括以下几个方面：（1）文献筛选：包括文献的检索、筛选和纳入；（2）文献的质量评估：包括随机对照试验、队列研究、病例对照研究等不同类型文献的质量评估；（3）数据提取和分析：包括数据的提取、整理和分析；（4）结果的报告和解释：包括结果的报告方式、如何解释结果等。
4.手册的评价标准和方法手册提供了一套详细的评价标准和方法，包括风险偏倚、质量评估、数据提取和分析等。
这些标准和方法被广泛接受和应用，是进行系统评价和荟萃分析的基础。
5.手册的优点和不足手册的优点在于提供了一套系统、全面、实用的评价方法和标准，对于提高研究的可靠性和质量具有重要的指导作用。
然而，手册也存在一些不足，例如部分内容较为复杂，对研究者的统计学和医学知识要求较高。
6.对我国相关领域的影响和启示Cochrane 文献评价手册对我国的医学研究、临床实践和卫生政策制定产生了深远的影响。
它提供了一种科学的、可靠的评价方法，有助于提高我国医学研究的质量和水平。
Cochrane RCT质量评价标准
在Cochrane图书馆中，对随机对照试验（RCT）的质量评价是至关重要的。
以下是一些关键的质量评价标准，主要包含以下几个方面：
1. 随机方法是否正确：
随机方法的描述是否清晰明确，易于理解？
随机序列的产生是否使用了合适的方法，如随机数字表、计算机生成的随机数等？
是否做到了分配隐藏，以避免分配意向的干扰？
2. 是否隐蔽分组：
分组是否做到了隐蔽，以避免选择性偏倚？
实施盲法的过程中是否考虑了所有涉及的人员，包括研究对象、试验人员、数据分析人员等？
3. 盲法的使用情况：
在试验过程中是否使用了盲法？
盲法的实施是否充分考虑了可能的破盲情况？
盲法的使用是否贯穿了整个试验过程？
4. 失访或退出描述情况：
在试验报告中是否详细描述了失访或退出的情况？
对于失访或退出的人员，是否进行了适当的处理，如ITT分析等？
5. 有无采用意向性（ITT）分析：
是否采用了意向性治疗分析（ITT）？
ITT分析的执行是否正确，如对所有随机分配的患者进行分析，无论他们是否接受了治疗等？
在评价RCT的质量时，需要综合考虑以上标准。
此外，还应关注其他因素，如研究对象的
招募、研究团队的资质和经验、研究的经费来源等。
这些因素都可能对试验的质量产生影响。
cochrane纳⼊的RCT⽂献质量评价（风险偏倚评估⼯具）中英⽂对照版..中⽂：Table 8.5.a: The Cochrane s tool for assessing riskTable 8.5.d: Criteria for judging risk ofbias in the assessment tool Risk of bias分配隐藏分配前不充⾜的分配隐藏导致选择偏倚Table 8.7.a: Possible approach for summarya ssessments of the risk of bias for each important outcome (across domains) within and across studies英⽂：Table 8.5.a: The Cochrane Collaboration ' s tool for assessing risk of biasTable 8.5.d: Criteria for judging risk of bias in the ‘Risk of bias ' assessment toolriskorsOTHER BIASTable 8.7.a: Possible approach for summary assessments of the risk of bias foreach important outcome (across domains) within and across studiesthose that were pre-specified (convincing text of this naturemay be uncommon).Criteria for theudgement o f ‘Highrisk of bias. Any one of the following: ' Not all of the study'-spse pcrifeied primary outcomes havebeen reported; One or more primary outcomes is reported using measurements,analysis methods or subsets of the data (e.g. subscales) thatwere not pre-specified;One or more reported primary outcomes were not pre-specified(unless clear justification for their reporting is provided,such as an unexpected adverse effect);One or more outcomes of interest in the review are reportedincompletely so that they cannot be entered in a meta-analysis;The study report fails to include results for a key outcomethat would be expected to have been reported for such a study.Criteria for the udgement of ‘ Unclear isk ' of bias.Insufficient information to permit judgement of ‘Low risk ' or ‘Hi It is likely that the majority of studies will fall into this category. gh risk。
