Management And Legal Issues In Surgery Flashcards
When is it mandatory to involve an independent mental capacity advocate ?
When a patient requires a significant intervention, time permits and the patient lacks capacity to decide for themselves When a patient cannot decide on the best treatment When parents disagree about treatment of a child When two doctors disagree about the best treatment option When a patient has lost trust in their clinician
When a patient requires a significant intervention, time permits and the patient lacks capacity to decide for themselves
The Mental Capacity Act (MCA) requires doctors to involve an independent mental capacity advocate (IMCA) for serious medical treatment decisions when:
a best interests decision is required because the doctor has assessed the person as not having the capacity to make the decision themselves
the person does not have family or friends with whom it is appropriate to consult about the decision.
A 6 year old is hit by a car and is brought to the emergency department. He is haemodynamically unstable with bilateral femoral shaft fractures and concerns that he may have a ruptured spleen. The parents have refused blood transfusions on religious grounds. What is the correct course of action?
Proceed with treatment Do not proceed with treatment Apply to court Apply for an IMCA Contact the PALS service
Proceed with treatment
In the UK, the GMC and common law advises that emergency life saving treatment can be given to a child irrespective of the parents views. There is clearly insufficient time here to apply to a court.
Which of the statistical tests listed below is most appropriate to use with data which follows a normal distribution?
T Test Fishers exact test Spearmans rank test Mann Whitney U test Bonferroni test
A T Test is most suited to data which follows the normal distribution as the others are non parametric tests. The Bonferroni test is used to provide correction when multiple tests are used.
A consultant surgeon is undertaking increasingly complex neonatal surgery. However, this is in breach of guidance following a series of adverse outcomes. Previously it had been stated that these should be performed with close supervision. Two further babies die and the surgeon still refuses to undertake these procedures under supervision. What is the correct course of action?
Review the cases at the next mortality and morbidity meeting Discuss the situation with the coroner Arrange for it to be discussed at the consultants next appraisal Discuss the matter with the General Medical Council Discuss the matter with the British Medical Association
Discuss the matter with the General Medical Council
It is likely that the practice restrictions were imposed by the GMC and given that there is an ongoing risk to patients and the surgeon is in breach of those practice restrictions, it would be appropriate to raise this with the GMC.
A surgeon has conducted a piece of research and is trying to make his non parametric data appear interesting for publication. To do this he is conducting multiple analyses of sub group data using multiple tests. Which of the tests listed below should be considered?
LSD post hoc test Bonferroni correction Unpaired T test Paired T test Chi squared test
Bonferroni correction
This is a process referred to as data dredging and can lead to erroneous results. Post hoc testing in general can be a problem in research and to try and minimise the potential for error some advocate the use of the Bonferroni method. This adjusts the test to take account of the number of tests that have been performed on the data.
Which of the following tests is most appropriate for correcting against multiple statistical analyses that might provide an erroneous result (i.e. to correct against data dredging)?
LSD post hoc test Bonferroni test T Test Fishers test Spearmans rank test
Bonferroni test
As more types of side effects are considered, it becomes more likely that the new drug will appear to be less safe than existing drugs in terms of at least one side effect. Methods are available to adjust the p value to reflect the multiple comparisons being made, the aim being to avoid spurious results. A frequently applied correction is the Bonferroni method in which the observed p values are multiplied by the number of tests performed, any resulting p value which is greater than 1 is set to 1 and any which remains at less than 0.05 can be considered significant at the 5% level.
If a sample is normally distributed which of the following is true?
Mean = standard deviation Mean = standard error of the mean Mean = median Mean = variance The mode and standard error of the mean have the same value
Mean = median
In a normally distributed sample, the mean, median and mode are the same.
What is the reciprocal of absolute risk reduction?
Odds ratio Number needed to treat False positive False negative None of the above
Number needed to treat
In epidemiology, the absolute risk reduction, or risk difference is the decrease in risk of a given activity or treatment in relation to a control activity or treatment. It is the inverse of the number needed to treat.
You have been asked to investigate the potential benefit of setting up a service to help patients with stomas in the local area. What is the most important factor when determining how many resources will be required?
Incidence Bayesian factor Prevalence Denominator data P value
Prevalence
In medical statistics, which of the following does a p value of 0.04 represent?
Risk of type 1 Error Risk of type 2 Error Size of power of the study Sample size Number of degrees of freedom
Risk of type 1 Error
P values are related to the significance levels of a statistical test and therefore are in effect measuring the risk of a type 1 error.
Which of the following statements relating to quantitative data is false?
Discrete data cannot be sub divided The median is less susceptible to extreme outliers than the mean The mean is susceptible to extreme outliers Data that fits the standard distribution perfectly will have a mode that is half the value of the mean Values obtained have a numerical scale
Data that fits the standard distribution perfectly will have a mode that is half the value of the mean
Data that fits the standard distribution perfectly will have a mean, median and mode that are all the same value.
A surgical department wishes to determine whether it is using types of prosthetic mesh material for incisional hernia surgery in the most effective manner. Recently there have been cases of non mesh usage and loss of material as a result of the implants being ‘out of date’. What is the most appropriate method to investigate this?
System based audit Standards audit Peer review Financial audit Operational audit
System based audit
This is primarily an issue of stock control. However, the system by which the materials are used within the theatre will need evaluation. Because it is the usage and stock that are a problem, rather than the sourcing the systems based audit will be more effective than an operational audit.
As the SpR in general surgery you wish to determine whether your breast cancer unit is complying with the British Association of Surgical Oncology guidelines for management of high grade ductal carcinoma in situ. What is the best course of action?
Undertake a clinical audit Undertake a clinical review Undertake a service evaluation Discuss the case with the ethics committee Discuss selected cases at joint histopathology meetings
Undertake a clinical audit
Since this comparison with practice against an agreed standard, the correct course of action is to undertake an audit.
What is the main impact of the Montgomery ruling in consenting patients for surgical procedures?
It clearly states that all risks however minor with a frequency of 10% or greater be disclosed It states whether a reasonable person in the patients position would be likely to attach significance to the risk, or the doctor is or should reasonably be aware that the particular patient would be likely to attach significance to it It states all procedures should be performed by a consultant It covers the decision making for minors who need to be consented by proxy It replaces the Gillick competency test
It states whether a reasonable person in the patients position would be likely to attach significance to the risk, or the doctor is or should reasonably be aware that the particular patient would be likely to attach significance to it
The new legal judgement recognises this individual approach to warning patients about risk. Rather than taking into account the percentage possibility of a risk arising, doctors need to bear in mind the significance of a given risk for that particular patient, and the nature of the risk, such as the effect it would have on the patient’s life if it were to occur. The assessment is therefore considered to be both fact-sensitive and sensitive to the characteristics of the particular patient.
A surgical team wish to conduct a meta analysis of randomised controlled trials of the use of low molecular weight heparins in the prevention of post operative deep vein thrombosis. How would these results be best displayed graphically?
Forest plot Box Whisker plot Violin plot Kaplan Meier graph None of the above
Forest plot
Data from multiple RCT’s are best displayed using Forest plots. Funnel plots may be used to determine the effect of small studies and their overall effect on the data. Violin plots and Box Whisker plots are often used to graphically display non parametric data from single studies and are not generally used to display data from meta analyses.
A rapid finger-prick blood test to help diagnosis deep vein thrombosis is developed. Comparing the test to current standard techniques a study is done on 1,000 patients:
DVT present DVT absent
New test positive 200 100
New test negative 20 680
What is the specificity of the new test?
680/880 200/220 680/780 680/700 200/300
680/780
Specificity = true negatives / (true negatives + false positives)
= 680 / (680 + 100)
A new test to screen for pulmonary embolism (PE) is used in 100 patients who present to the Emergency Department. The test is positive in 30 of the 40 patients who are proven to have a PE. Of the remaining 60 patients, only 5 have a positive test. What is the sensitivity of the new test?
8.33% 30% 40% 66.66% 75%
75%
Sensivity = True positive/(True positive + False Negative)
The sensitivity is therefore 30 / (30 + 10) = 75%
A surgical unit are conducting a study to determine whether patients who have bowel preparation have a lower risk of colonic anastomotic leakage than those having none. The planned sample size is 25. Which of the tests below is most appropriate?
Paired T test Unpaired T test Fishers exact test Chi squared test LSD post hoc test
Fishers exact test
It is likely to be underpowered with the number provided. However, it would be possible to classify such data into a 2x2 contingency table. However, when the sample size is small, the Chi squared test is not suitable and in these situations the Fishers exact test is used.
A 46 year old man is undergoing a colonoscopy under sedation using a combination of midazolam and fentanyl sedation. The procedure is complicated by the development of a significant sigmoid loop and becomes increasingly uncomfortable. When the endoscope is in the region of the colonic splenic flexure, the patients asks for the procedure to stop. What is the best course of action?
Administration of additional midazolam and proceeding to complete the procedure Withdrawal of the endoscope and arranging an alternative test Call an anaesthetist to administer an general anaesthetic Administration of intravenous fentantyl and proceeding to complete the procedure Turn the patient prone and complete the procedure
During endoscopic procedures, many patients have conscious sedation and retain decision making ability. If the request the procedure to be stopped this must be adhered to.
Which one of the following statements best describes a type II statistical error?
The p value fails to reach statistical significance The alternative hypothesis is rejected when it is false The null hypothesis is rejected when it is true The null hypothesis is accepted when it is false None of the above
The null hypothesis is accepted when it is false
A patient involved in a national research trial of surgery versus conservative management for ruptured abdominal aortic aneurysms dies during surgery because the surgeon decided to deviate from the study protocol and implant a different type of graft material. What is the correct course of action?
Refer the surgeon to the GMC Report the case to the ethics committee that gave a favorable opinion for the study Report it to the responsible officer for the hospital Report it to the Caldicott guardian for the hospital Report it to the media
Report the case to the ethics committee that gave a favorable opinion for the study
Where a research participant experiences an adverse outcome, the correct course of action is to refer to the ethics committee that approved the study. Minor adverse effects are usually reviewed by the data monitoring committee and reported annually. However, a serious event is reported immediately. It would not be appropriate to refer to the GMC though, it may be that the surgeon deviated from the protocol for good reason.
As part of a research project you are trying to ascertain whether the use of dummies in infants is linked to sudden infant death syndrome. What is the most appropriate form of study design?
Randomised controlled trial Cross-over trial Cross-sectional survey Case-control study Cohort study
Case-control study
As sudden infant death syndrome is relatively rare a case-control design is more appropriate than a cohort study.
Which of the following has the greatest impact on the positive predictive value of a test?
Prevalence Subjects who are true negatives Specificity Relative risk None of the above
Prevalence
The positive predictive value (PPV) is the probability that an individual with a positive screening result has the disease. The sensitivity is the probability that an individual with the disease is screened positive and the specificity is the probability that an individual without the disease is screened negative.
Its value depends upon the prevalence of the condition being tested for and the sensitivity of the test used.
Considering cluster randomised trials, which of the following statements is false?
They consider interventions targeted at groups They require increased recruitment to achieve the same level of statistical power as individual trials If results are analysed on an individual basis a lower P value may be obtained They are less prone to unit of analyses errors than trials involving individual observations The statistical analyses for these trials is more complex than that required for trials based on individuals
They are less prone to unit of analyses errors than trials involving individual observations
Cluster randomised trials are more prone to unit of analyses errors than individual based trials. Clustering needs to be considered in trial design and data analysis. One of the commonest errors is where a study is a cluster study but researchers have failed to recognise this fact. This will then result in the incorrect analysis being pursued. A lower P value will then result and a false positive error will occur.
In a randomized study of chemotherapy drugs for bowel cancer, a group receiving treatment A had a recurrence rate of 12.5% and a group receiving treatment B had a recurrence rate of 15%. Both groups are matched for size and length of follow up. What is the number needed to treat to prevent a recurrence?
2.5 25 4 40 5
40
There is an absolute risk reduction of 15-12.5%= 2.5% for treatment A
Therefore the NNT = 1/0.025 = 40
A new blood test to screen patients for colorectal cancer is trialled on 500 patients. The test was positive in 40 of the 50 patients shown to have colorectal cancer by colonscopy. It was also positive in 20 patients who were shown not to have colorectal cancer. What is the positive predictive value of the test?
0.8 0.66 0.33 0.1 Cannot be calculated
0.66
A contingency table can be constructed from the above data, as shown below:
Colorectal cancer No colorectal cancer
Test positive 40 20
Test negative 10 430
Positive predictive value = TP / (TP + FP) = 40 / (40 + 20) = 0.66
Which of the following statements relating to randomised controlled trials is false?
Consist of a control group recruited during the same time interval as the treatment group. Are not applicable to retrospectively analysed data even if captured on a prospectively created database. They require concealment of treatment throughout the duration of the study. They require concealment of treatment until after randomisation. They are less susceptible to researcher bias than non-randomised controlled trials.
They require concealment of treatment throughout the duration of the study.
An RCT does not have to include concealment although many medical trials may do so. Indeed in the case of surgical research it may not be practicable or possible to include concealment in the protocol. This does not mean that the trial is not an RCT, simply that it is not blinded.
Which of the following most closely describes the risk of a type I statistical error?
Power calculation P value Odds ratio Relative risk None of the above
P value
Type 1 errors occur when a test rejects a true null hypothesis and is therefore related to the significance level of the test result. To explain consider the following arbitrary example.
We hypothesise that bowel preparation vs no bowel preparation has no effect on anastomotic leak rates following left hemicolectomy. If we compare the rates of anastomotic leak and perform a Chi Squared test and obtained a P value of 0.95 we should conclude that we unable to reject the null hypothesis. Should we choose to do so then we are at risk of committing a type 1 error. In reality the knowledge that a type 1 error was committed is usually some time after the event. When other studies have been performed that have shown an effect.
5 surgeons in a colorectal unit wish to determine whether there is a significant difference in their individual leak rates for anterior resection of the rectum. Which of the following investigations is most appropriate?
Paired T Test Unpaired T test Chi squared test Fishers exact test Kruskall Wallis test
Kruskall Wallis test
In this scenario the data is derived from 5 groups of surgeons. If the data were normally distributed then an ANOVA could be considered. Since these assumptions cannot be met, or satisfied by transforming the data then the Kruskall-Wallis test provides a non parametric alternative. This is essentially an extension of the Wilcoxon Rank sum test and detects differences in median values between each group. To compare more accurately differences between two individual surgeons a Mann Whitney U test may be a more acceptable alternative.
A cohort study is being designed to look at the relationship between smoking and breast cancer. What is the usual outcome measure in a cohort study?
Odds ratio Experimental event rate Relative risk Absolute risk increase Numbers needed to harm
Relative risk
Cohort studies - relative risk
A group of surgeons conduct a meta analysis of randomised controlled trials comparing the use of analgesic regimes following laparoscopic cholecystectomy. What level of evidence is provided by such an analysis?
V I II III IV
Levels of evidence
I - evidence from meta-analysis of randomised controlled trials
II - evidence from at least one well designed controlled trial which is not randomised
III - evidence from correlation and comparative studies or use of historical controls
IV - evidence from case series
V - Expert opinion or founded on basic principles
Surgeons are becoming increasing concerned about the adverse results of Mrs X performing a new an innovative operative procedure not widely practised elsewhere. What is the most appropriate investigation?
Peer review Standards audit System based audit Operational audit Financial audit
Peer review
In the situation where a surgeon performs an unfamiliar procedure, a peer review is often the best way to evaluate the problem. This does not have to be externally based, but often is.
Which one of the following is equivalent to the pre-test probability?
Post test odds / (1 + post-test odds) Pre-test odds x likelihood ratio The prevalence of a condition The incidence of a condition Post-test odds / likelihood ratio
The prevalence of a condition
The prevalence is the proportion of a population that have the condition at a point in time whilst the incidence is the rate at which new cases occur in a population during a specified time period.
You are performing a study of weight in patients attending pre operative assessment clinic for elective knee replacement. Assuming that the results are normally distributed, what percentage of values lie within two standard deviations of the mean weight?
95.4% 5.3% 98.3% 10% 97.5%
95.4%
In statistics, the 68-95-99.7 rule or three-sigma rule, or empirical rule states that for a normal distribution, nearly all values lie within 3 standard deviations of the mean.
About 68.27% of the values lie within 1 standard deviation of the mean. Similarly, about 95.45% of the values lie within 2 standard deviations of the mean. Nearly all (99.73%) of the values lie within 3 standard deviations of the mean
In Intention to treat analysis, which statement is untrue?
It is based on the initial treatment intended. Excludes those who cross over to alternative treatment arms of a trial. Is different from a per protocol analysis. Will affect the statistical power calculation to compare outcomes of treatment. Helps to minimise observer bias.
Excludes those who cross over to alternative treatment arms of a trial.
An intention to treat analysis considers data according to the treatment to which the patient was randomised, rather than the treatment which was recieved.
It includes those who cross over which is how it helps provide additional information relating to those groups.
Which of the following is not usually required to make a power calculation?
The specificity of the intervention being tested The desired significance level The size of the effect being measured The desired power value Sample size used to detect the effect
The specificity of the intervention being tested
The specificity of a test is related to type 1 errors.
The components that are nearly always needed for power calculations are : Size of effect Significance level Sample size used to detect the effect Desired power value
A new hernia mesh designed to prevent the risk of infection undergoes clinical trials. One hundred patients are given the new mesh. During a three month period 10 of the patients have an episode of infection. In the control group there are 300 patients who are given a placebo. In this group 50 people have an infection during the same time period. What is the relative risk of having an infection when the new mesh is used?
0. 8 0. 2 1. 66 0. 6 0. 06
0.6
Experimental event rate, EER = 10 / 100 = 0.10
Control event rate, CER = 50 / 300 = 0.166
Therefore the relative risk = EER / CER = 0.1 / 0.166 = 0.6
Which of the following statements relating to audit and governance is untrue?
An audit standard is a threshold of compliance with an audit criterion Sample size calculations are an important part of audit planning Clinical audit is part of clinical governance Audits should be performed regularly when a novel surgical technique is introduced and where there is little knowledge of anticipated complications or outcomes An audit criterion is a measurable outcome of care, aspect of practice or capacity
Audits should be performed regularly when a novel surgical technique is introduced and where there is little knowledge of anticipated complications or outcomes
Audits should compare performance against known standards. Where a novel technique is being introduced standards are unlikely to exist, sample sizes cannot therefore be accurately calculated. This is an example of research, which is not an audit.
Which of the following statements relating to qualitative data is false?
The data has no true numerical scale It may comprise multiple data groups May be reported using odds ratios May be reported using frequency histograms It is best analysed statistically using a students T test when multiple factors are present
It is best analysed statistically using a students T test when multiple factors are present
The students T test should be performed if two sets of data have a normal distribution, the T test cannot be used to analyse multiple data sets.
Which of the following statements is false in relation to consent?
All adults by law are assumed to be competent The Bolam test defines if a patient has capacity or not Consent 2 is the form signed by parents on behalf of their children Implied consent is a form of consent Consent 4 is the form signed when a patient is unable to consent for a treatment or investigation
The Bolam test defines if a patient has capacity or not
The Bolam test defines if a decision made by a doctor is in agreement with the professional standard of medical practise.
