Clinical Research Methods.

Question 1                                       [10]

Match the study types to the studies described below:

1. A study is designed to assess the impact of sun exposure on skin damage in beach volleyball players. During a weekend tournament, players from one team wore waterproof, SPF 35 sunscreen, while players from the other team did not wear any sunscreen. At the end of the volleyball tournament players’ skin from both teams was analysed for texture, sun damage, and burns. Comparisons of skin damage were then made based on the use of sunscreen.
2. A study was developed to asses characteristics associated with a history of suicide attempts amongst psychiatric outpatients. Socio-demographic, clinical and behavioural characteristics were obtained from all patients and compared in relation to any history of suicide attempts.
3. In order to determine whether parental divorce during childhood may be associated with subsequent suicidal behaviour, a study followed up on all children from a community whose parents had divorced during their childhood, versus those whose parents remained married through childhood.
4. To test a newly developed sunscreen, a group of sailors in an international race were allocated to either the new sunscreen or a well-known brand and then evaluated for sun damage at the end of their 3 month trans-Atlantic sailing trip.
5. All office workers in a building were asked about their back pain symptoms and risk factors in order to assess the need for ergonomic work stations.
6. Several studies have been undertaken to assess office workers’ ergonomics and their association with back pain. Your CEO asks you to conduct a study looking at this research to help guide their decision about buying new work stations.
7. Morphine and benzodiazepines are commonly used agents for pain control during reduction of shoulder dislocations. A study is conducted to assess usage of these agents in city-wide hospitals during an international sports event.
8. A study looks at clients referred for depression to a community health centre. On arrival, those with odd dates of birth are taught self-meditation techniques in addition to the standard counselling given to those with even dates of birth.
9. Women on oral contraceptive pills may be more likely to develop pulmonary embolus on long flights. By looking at all women who present with pulmonary emboli after a flight, and especially their contraceptive history, researchers hope to quantify this association.
10. Women on oral contraceptive pills may be more likely to develop pulmonary emboluson long flights. By looking at all women taking oral contraceptives, and collecting data on how many of them develop pulmonary emboli after a flight, over a ten year period, researchers hope to quantify this association.

Question 2                                       [16]

Coffee is a major source of caffeine, which has been shown to acutely reduce sensitivity to insulin, but also has potentially beneficial effects. A study investigated the association between coffee consumption and risk of clinical type 2 diabetes in a Dutch town with 17 111 participating men and women aged 30-60 years. There were 4255 participants who reported drinking more than 7 cups of coffee a day. After 10 years of follow up, 306 new cases of type 2 diabetes were reported, of whom 63 consumed more than 7 cups of coffee a day.

(modified abstract Lancet 2002)

• Write a research question for the study. [3]
• What type of study is this? And how will you look for association? [2]
• Calculate the incidence of NIDDM at the end of the study. [2]
• Draw up a 2×2 table for the data given and determine the association [6]
• Explain, using your calculation of association, whether coffee is a good thing or not in this study and how you will translate this to your own coffee drinking. Mention any other issues to consider in assessing the relevance to your own coffee consumption.[3]

Question 3                                       [14]

A population-based study of rheumatoid arthritis (RA) was conducted in a community. They compared 349 incident cases of rheumatoid arthritis with 1,458 controls (without RA) selected by random selection from the community database. They conducted personal interviews to collect data on weight, smoking, alcohol history, reproductive variables, and other demographic variables from all participants.  (modified abstract Epidemiology 1994)

• Write a research question for the study [2]
• What type of study is this and why? And what measure of association would you use

to assess risk factors?                                                                                                  [2]

• Interpret the table below for the results of this study as to whether smoking (past or current) is associated with RA compared to those who have never smoked. Use the appropriate measure of association to calculate whether smoking (current or former) affects the risk of developing RA and interpret in your own words. [8]

• Name any bias effects might be at play that could affect the results of this study and explain? [2]

Question 4:                                       [8]

From the list of biases below, choose the most appropriate one for each example (each type of bias should be used only once):

• A case-control study is conducted to test if oral contraceptives (OC) are a risk factor for endometrial cancer. A group of cases and an equal number of controls are selected. Cases are selected at GP (family doctor) surgeries. Cases who use OC may be more likely to be offered screening for endometrial cancer either systematically or because of a side-effect of OC (breakthrough bleeding). The chance of undergoing detection of endometrial cancer is therefore higher among OC users than among other cases i.e. the use of OC may cause the search for endometrial cancer rather than causing the cancer itself. The result is that a higher proportion of cases diagnosed with endometrial cancer report using OC.
• When the subjects who offer to participate in a research project are different in some ways from the general population. If this occurs, the researcher has sampled only a subset of the population, and consequently, the data gathered are not representative of all people, merely of those that choose to volunteer.
• When a group of workers in an industry find out that one of the chemicals they have been exposed to is a carcinogen, then these workers might present to a medical facility sooner, or be more likely to attend screening, than a non-exposed population. Also, medical staff might more readily suspect these individuals than others to have cancer, because of the knowledge of their exposure to the carcinogen, and this might influence what tests are done and how quickly they are ordered.
• A study of hand-washing among medical staff found that when the staff knew they were being watched, compliance with hand-washing was 55% greater than when they were not being watched.
• In the early 2000s, there was considerable publicity arising from a claim that the measles, mumps and rubella (MMR) vaccine was related to and possibly caused autism in children (the originating claim was subsequently found to be based on fraudulent data and the publication was withdrawn) (Andrews 2002). Researchers found that parents of autistic children diagnosed after the publicity tended to recall the start of autism as being soon after the MMR jab more often than parents of similar children who were diagnosed prior to the publicity.
• A meta-analysis of body size and development of prostate cancer found that the criteria used to define nonaggressive and aggressive prostate varied between cohorts.
• Larger men have bigger prostates, which makes diagnosing prostate cancer via biopsy more difficult (it is harder to hit the target on biopsy). Therefore, men with larger prostates are less likely to be accurately diagnosed with prostate cancer. Thus, a real association between obesity and prostate cancer risk may be underestimated. This was shown by researchers who found that obesity increased prostate cancer risk. Without accounting for the size of the prostate, however, the relationship between obesity and prostate cancer was under-estimated.
• CT or MRI imaging for evaluation of headache discovers an asymptomatic maxillary sinus mucus retention cyst.

Question 5:                                        [10]

• In each of the following study types, name two of the most common biases associated with the study type. Provide a brief description of each bias and explain how you will minimise the impact of each during the design phase:
  1. Case-control study                                                                         [4]
  2. Cohort study                                                                         [4]

• Explain the role of randomisation and allocation concealment in terms of minimising bias. [2]

Question 6:                                          [2]

Briefly describe the impact that positive result publication bias has on evidence-based

practices.                                                                                                                     [2]

Question 7:                                     [10]

• Breast cancer is the leading cancer in females in South Africa and affects all races. One in 31 women will be diagnosed with breast cancer but early detection can ensure a 95% chance of successful treatment. Explain in your own words the differences

between a screening test and a diagnostic test and provide examples related to breast

cancer.                                                                                                             [6]

• Explain the advantages and disadvantages of mammography as a screening test if it is

99% sensitive but only 81% specific.                                                             [2]

• In terms of sensitivity, specificity, NPV and PPV, what would constitute:
  1. the ideal screening test, and
  2. the ideal diagnostic test.                                                                    [2]

Question 8:                                      [10]

Read through the abstract below and then answer all the questions:

Mandibular fractures are one of the most frequently seen injuries in trauma. In terms of facial trauma, mandible fractures constitute 40%–62% of all facial bone fractures. The tongue blade test (TBT) has been shown to be a sensitive screening tool when compared with plain film Xrays. However, recent studies have demonstrated that computed tomography (CT) scan is more sensitive for determining mandible fractures than the traditionally used plain film Xrays. The purpose of the study was to determine the sensitivity and specificity of the TBT as compared with the new gold standard of radiologic imaging, CT scan. Any patient suffering from facial trauma was prospectively enrolled during the study period at a single urban, academic Emergency Department. A TBT was performed by the resident physician and confirmed by the supervising attending. CT facial bones were then obtained for the ultimate diagnosis. One hundred and ninety patients were included during the course of the study. Of the patients enrolled, there were 95 true positives and 29 false positives using the TBT. 61 Patients had normal CT scans and negative TBT’s.

• Tabulate the results in a 2×2 table and calculate sensitivity, specificity, NPV and PPV.

[2+4]

• Based on the evidence of this study, would you advocate the use of a TBT in your

emergency centre. Explain your answer.                                                                    [2]

• What is the prevalence of mandibular fractures in the study and how would it have changed your answer above 2) if the prevalence of mandibular fractures in facial

trauma in your setting was less than 10%?

Clinical Research Methods

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