Statistics used for evaluating a study including relative risk reduction (RRR), absolute risk reduction (ARR), and number needed to treat (NNT).
Which one of the following is the correct formula for calculating NNT?
Correct Answer C:
The absolute risk reduction (ARR) is the difference in the outcome event rate between the control group and the experimental group in a given study. The relative risk reduction (RRR) is the percent reduction in the measured outcome between the experimental and control groups. In evaluating a clinical study, the single most clinically useful statistic may be the number needed to treat (NNT). The NNT is the number of the patients who must be treated to prevent one adverse outcome, or the number of patients who must be treated for one patient to benefit. The NNT is simply the inverse of the ARR. Thus, 1/ARR is the correct formula for calculating NNT.
Results of a clinical study show a relative risk reduction (RRR) of 33% and an absolute risk reduction (ARR) of 20%. There are 1000 patients each in the treatment and control groups. To help determine the potential benefit of the treatment it is necessary to identify the number needed to treat (NNT).
Which one of the following is the NNT for this clinical study?
Correct Answer B:
The number needed to treat (NNT) is one of the most useful calculations for assessing the benefit of a treatment. Simplified, the NNT is the number of patients necessary to treat in order for one patient to benefit. The relative risk reduction (RRR), often quoted in the press or by those promoting a treatment, can be misleading to both the general public and to physicians. Much more useful is the absolute risk reduction (ARR); NNT is the mathematical reciprocal of ARR (i.e., 1/ARR).
In this case it's 1/0.2 = 5 OR 100/20=5
The statistical measure of the degree of relationship between two sets of numbers is:
Correct Answer E:
In epidemiology, the ‘correlation coefficient’, indicates the strength and direction of a linear relationship between two random variables.
In general statistical usage, correlation or co-relation refers to the departure of two variables from independence. In this broad sense there are several coefficients, measuring the degree of correlation, adapted to the nature of data.
An elderly man with cancer of the prostate and metastasis, is now complaining of increased intolerable back pain and constipation. He states he is already tired of all aggressive treatments.
What is the best initial therapy for this patient's condition?
No treatment has been proven to increase the life expectancy of patients with spinal metastasis. The goals of therapy are pain control and functional preservation. The most important prognostic indicator for spinal metastases is the initial functional score. The ability to ambulate at the time of presentation is a favorable prognostic sign. Loss of sphincter control is a poor prognostic feature and mostly irreversible.
For this patient, the best initial therapy is dexamethasone (choice C). Steroid therapy is effective in treating bone pain. Of all the corticosteroids, dexamethasone has the least mineralocorticoid effect and is least likely to be associated with infection or cognitive dysfunction. Complications from treatment with dexamethasone are likely to occur after 3 weeks of treatment. In about 70-80% of patients, symptoms improve within 48 hours of treatment.In most patients, steroid use must be continued until radiotherapy is completed.
→ Radiation therapy (choice A) is the mainstay treatment preferred in bone metastases. CT or MRI of the spine should be done first to precisely know the location of tumor and critical normal structures. The traditional treatment plan, or radiation port, is to include 2 vertebral bodies above and 2 below the lesion. This range is based on the fact that recurrence is most common in bodies contiguous to the site of involvement. While this treatment may eventually be done for this patient, the best initial treatment is dexamethasone.
→ Morphine to relieve pain (choice B) is likely to worsen the patient's constipation. The severity of pain in these patients makes treatment with strong opioids an important option and often laxatives are considered in constipated patients who need morphine, while this patient may eventually have to opt for that option, out of the choices we have here dexamethasone is the best initial treatment.
→ Lidocaine patch (choice D) is less effective than dexamethasone in relieving pain in these patients.
→ Chemical epidural neurolysis (choice E) is infrequently used to treat medically intractable pain. It is effective for interrupting single or multiple radicular pain, but it poses a risk of acute deterioration especially when structural instability or compression is present.
You are caring for a 70-year-old male with widespread metastatic prostate cancer. Surgery, radiation, and hormonal therapy have failed to stop the cancer, and the goal of his care is now symptom relief. He is being cared for through a local hospice. Over the past few days he has been experiencing respiratory distress. His oxygen saturation is 94% on room air and his lungs are clear to auscultation. His respiratory rate is 16/min.
Which one of the following would be best at this point?
Correct Answer A:
Dyspnea is a frequent and distressing symptom in terminally ill patients. In the absence of hypoxia, oxygen is not likely to be helpful. Opiates are the mainstay of symptomatic treatment. Morphine is very effective in reducing the patient's anxiety, easing breathing, and improving blood flow (acts as a venous vasodilator).
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