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A Drug for Platelets Platelets are an important part of the blood because they cause the blood to clot when that is needed to stop bleeding. The drug eltrombopag (which we shall henceforth refer to as EL), was tried on patients with chronic liver disease who were about to be operated on to see whether it would prevent the need for transfusion of platelets during the surgery and shortly thereafter. Read the following excerpt from the abstract that accompanied this study, and answer the questions below. "Methods: We randomly assigned 292 patients with chronic liver disease of diverse causes and platelet counts of less than 50,000 per cubic millimeter to receive EL, at a dose of \(75 \mathrm{mg}\) daily, or placebo for 14 days before a planned elective invasive procedure that was performed within 5 days after the last dose. The primary end point was the avoidance of a platelet transfusion before, during, and up to 7 days after the procedure. Results: A platelet transfusion was avoided in 104 of 145 patients who received EL (72\%) and in 28 of 147 who received placebo \((19 \%)(\mathrm{P}<0.001) . "\) (Source: Nezam Afdhal et al. 2012 . Eltrombopag before procedures in patients with cirrhosis and thrombocytopenia. New England Journal of Medicine \(367,716-724 .)\) a. Identify the treatment variable and the response variable. b. Was this a controlled experiment or observational study. Explain. c. Do the sample percentages suggest that the drug was effective in reducing the chance of needing platelet transfusions? d. What does the small p-value show? c. Can you conclude that the use of EL reduces the chance of needing a platelet transfusion? Why or why not?

Step by step solution

01

Identifying the Variables

In this study, the treatment variable is the administration of the drug eltrombopag, and the response variable is whether or not a platelet transfusion was required during and following surgery.

02

Determining the Study Type

This was a controlled experiment. This can be determined by noting that the researchers actively manipulated the treatment variable (the administration of eltrombopag or a placebo) and randomly assigned patients to either treatment group, which allows for the establishment of cause and effect relationships.

03

Interpreting Sample Percentages

By comparing the percentages of patients who avoided a platelet transfusion in both groups, it seems that the drug was effective in reducing the need for platelet transfusions. More specifically, 72% of patients receiving eltrombopag (EL) avoided a platelet transfusion compared to 19% of patients who received the placebo.

04

Understanding the P-Value

A p-value of less than 0.001 indicates there is a very low probability that the observed results occurred by chance. It offers strong evidence against the null hypothesis, which assumes there is no effect from the treatment.

05

Drawing a Conclusion

Based on the percentages and the low p-value, we can conclude that the use of EL appears to reduce the need for a platelet transfusion. However, before establishing a definitive cause-and-effect relationship, more research may be needed to account for confounding variables and uncertainty. It's also important to note that conclusions from statistical analyses should not replace clinical judgement.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Treatment Variable

In the context of the study exploring eltrombopag (EL) as a treatment for patients with chronic liver disease, the treatment variable is a pivotal aspect of the experiment design. A treatment variable is essentially what researchers manipulate or control to observe its effects on another variable.
Here, the treatment variable is the actual administration of the EL drug at a dosage of 75 mg daily. Participants of the study were divided into two main groups: those receiving the drug and those receiving a placebo. By controlling this variable, researchers can carefully assess the difference in outcomes directly attributable to the EL medication, rather than other external factors.
This manipulation helps to shed light on how the drug influences the patients' need for platelet transfusions, making it central to understanding the effectiveness of the treatment.

Response Variable

The response variable in any experiment represents the outcome or effect observed due to the manipulation of the treatment variable. In this controlled study, the response variable is whether or not a patient requires a platelet transfusion during or after the surgery.
The primary goal is to measure the EL drug's effectiveness in minimizing the need for such transfusions.

• If fewer transfusions are needed in the group receiving EL compared to the placebo group, it indicates a positive response to the treatment.
• The specific percentages of patients not needing a transfusion—72% for those on EL and 19% for the placebo group—highlight this variable's critical role in assessing treatment impact.

Understanding the response variable is crucial as it provides concrete data around which the effectiveness of the treatment, as well as the result of the entire study, is evaluated.

P-Value

The p-value plays an essential role in statistical analysis, helping determine the significance of the experiment results. In this study, a p-value of less than 0.001 indicates a very strong evidence against the null hypothesis. The null hypothesis typically would suggest that EL has no effect on the need for platelet transfusions.
A small p-value such as this one suggests that the likelihood of obtaining the observed outcomes under the assumption of the null hypothesis is extremely low. This indicates a significant difference between the treatment groups and supports the conclusion that EL administration possibly leads to fewer required transfusions.
Utilizing the p-value results in appreciating whether the observed difference is meaningful or merely due to random chance. Hence, scientists or researchers can make more informed decisions regarding the effectiveness of the treatment based on statistical evidence rather than assumptions or speculation.

Statistical Analysis

Statistical analysis is a powerful tool used to deduce conclusions from data sets in scientific research. In this experiment, statistical analysis helps in interpreting data collected from patients receiving both EL and placebo, comparing outcomes, and assessing the effectiveness of treatment.
Data regarding the percentages of patients who avoided a platelet transfusion effectively show that 72% of patients treated with EL did not need a transfusion, whereas only 19% of those given a placebo avoided one.

• This analysis involves descriptive statistics, which summarise the basic features of the data.
• Inferential statistics are then employed to make predictions or inferences about a larger population from the sample data.

Statistical analysis is fundamental not only to verify the validity of the experiment's results but also for enabling researchers to formulate reliable conclusions and contribute to broader scientific knowledge. It ensures the experiment findings are robust, accurate, and applicable within the context they were designed to examine.