研究的特色及局限性
再严谨的研究都会存在一定的局限性，因此，论文需要明确给出本研究的局限性。这不仅可以体现作者对于自己的研究足够熟悉，而且使得论文读起来更加严谨和充实。这些局限性自身也具有价值，它们可以为研究者自己或其他研究人员提供“线索”，有利于今后开展更加严谨的研究。此外，越来越多的期刊明确要求：说明自己的研究存在哪些优势或特色（strengths）。例如，研究人群具有代表性、数据收集方法较新颖。任何一个研究的开展都是有意义的，你要向编辑和审稿人推销你的论文，就需要十分明确地提出你的研究有哪些优势或特色及其对科学进步所做出的贡献。
撰写局限性时，要把握好一个度：一方面，不能避而不谈（这会让编辑认为你不够严谨）；另一方面，也不能满篇局限性（这会让编辑质疑研究的严谨性和可信度）。一般情况下，在撰写完一个局限性之后，对出现此局限性的原因进行解释（justify），说明在选择此方法时，是经过深思熟虑的。同时，尽量针对此局限性提出改进建议。研究的局限性，一般从研究设计、研究对象（抽样方法、样本量）、测量方法等展开。
如示例2-71所示，本研究首先给出了研究的局限性，包括①研究设计：研究采用了横断面设计（cross-sectional），限制了研究的因果推断。②抽样方法：研究采用了方便抽样法，研究对象来源于社区，代表性不强。同时，作者介绍了为降低此局限性做出的努力：通过从不同地区抽样，减少此局限性带来的影响。③测量方法：该研究所测量的概念具有文化差异，研究结果可能不适用于其他国家。④混杂变量：研究可能遗漏了重要的影响因素。同时，作者还给出了研究的特色，例如：使用了信效度较高的研究工具、样本量足够大。
示例2-71 研究的特色及局限性举例1
Strengths and limitations
The limitations of the study include the cross-sectional nature of the data，which limits interpretation of causal relationships.Second，participants were recruited mainly from community settings，which may have resulted in a sample with different characteristics from the general MCC population.We tried，however，to counterbalance the convenience sample by recruiting participants from different regions in Southern and Central Italy.Third，self-care and related variables are sensitive to sociocultural influences，so caution is needed when generalizing our findings to other countries.Finally，we considered only a limited number of self-care determinants；research on other possible influencing factors is needed.In particular，self-efficacy and psychological distress should be considered in future studies.
Strengths of the study include the use of theoretically grounded instruments，multicenter enrolment，robust sample size，and the enrolment of dyads similar to those described in different contexts.(https://www.daowen.com)
在撰写研究的特色和局限性时，要注意二者的顺序。虽然没有硬性规定，但是一般情况下先讲特色，再引出局限性。正如进行评审一样，先总结优点，再提出不足。这种撰写方式层层递进，逻辑性更强。如示例2-72所示，作者首先介绍了研究的特色，包括：多中心、大样本；且各个中心使用的研究方案一致。以此为基础，提出研究的局限性。针对第一个局限性，作者首先对此局限性进行了介绍，紧接着话锋一转，给出了“然而（Nevertheless）”，说明这个局限性带来的影响较小。类似地，针对第三个局限性，作者提出了使用“respiratory polygraphy”这种测量方法可能存在“低估OSA严重度”的局限性，但是紧接着又解释了采用此方法的原因。
示例2-72 研究的特色及局限性举例2
The strengths of our study include its multicenter design with a large patient population.All participating centers used the same methodology，and the sleep study was done with the same polygraph model.Nevertheless，this study has several potential limitations.First，we excluded patients with severe ACS and very poor prognosis（cardiogenic shock）as these patients have poor expectations for short-term outcomes.Additionally，we excluded patients with daytime sleepiness who exhibited the most severe OSA.From an ethical perspective，the OSA patient with an Epworth Sleep Scale score＞10 should continue to be treated with CPAP.Our results apply only to non-sleepy OSA patients.Nevertheless，the number of patients excluded for these causes was relatively low.Second，patients in this study were predominantly men；therefore，the results cannot be extrapolated to women.Third，the diagnosis is based on respiratory polygraphy，which could underestimate the severity of OSA.However，full polysomnography monitoring could be a stressful procedure for this high-risk patient group.Moreover，although full polysomnography monitoring is the recommended method for the diagnosis of OSA，data from 2017 suggest that respiratory polygraphy could also be used.
当然，如果研究没有明显的特色，可以不写，直接给出研究的局限性。如示例2-73所示，作者开门见山，给出了研究的局限性。提出了研究对象依从性不够高（non-completion），但是作者通过引用其他研究，说明自己研究中的依从性不高与既往研究类似，这就缓解了此局限性带来的冲击。另外，作者还针对此局限性提出了改进建议。
示例2-73 研究的局限性
This study had several limitations.Although the noncompletion rate was similar to that for other AUD gabapentin treatment trials37，38 and a National Institutes of Health National Institute on Alcohol Abuse and Alcoholismsponsored large multisite study，47 it should be noted that 13of 44（30%）of individuals on gabapentin and 18of 46（39%）on placebo did not complete the trial.Perhaps，adding other supportive counseling or Alcoholics Anonymous attendance could increase retention in treatment.Also，self-reported alcohol withdrawal symptoms prior to study entry might not fully capture the extent of withdrawal severity.In addition，those with complex psychiatric and medical conditions，including history of alcohol withdrawal seizures，were excluded.Furthermore，given its kidney excretion，gabapentin should be studied in patients with AUD with more severe liver disease，a condition in which medications are greatly needed.