Let us look at the sample NBME question below:

A randomized controlled trial is conducted to compare a new oral proton pump inhibitor with oral omeprazole for the prevention of recurrent duodenal ulcer bleeding. A total of 2000 patients with newly diagnosed duodenal ulcer who have had recent bleeding are randomly assigned to receive the new drug or omeprazole. After 1 month, results show that 4% of patients treated with the new drug have recurrent ulcer bleeding compared with 5% of patients treated with Omeprazole (p<0.05). Based on these results, how many patients would need to be treated with the new drug to prevent one recurrent duodenal ulcer bleed?

A.    A. 10

B.    B. 40

C.    C. 50

D.    D.100

E.     E. 200

Dissecting the question

The question targets number needed to treat.

To answer this type of question asking “Number Needed to Treat” you need to remember Absolute Risk Reduction [ARR] (That is how much risk is taken away after exposure or treatment, ARR is gotten when the exposed group is subtracted from the unexposed group)

The formula for Absolute Risk Reduction (ARR): Unexposed group – Exposed group = ARR

To get absolute risk reduction from the question, we need the number of patients who were treated with a new drug (4%) and the number of patients treated with Omeprazole (5%).

ARR = 5 – 4 = 1%

Convert percentage to number = 1/100 =  0.01

The formula for Number Needed to Treat: 1 / ARR

Number needed to treat = 1/0.01 = 100

The answer is D.100

Answering Biostatistics questions for IFOM and the USMLE: Part 1

Let us look at the sample NBME question below:

A community public health department has a limited budget for new interventions and must decide between two options. Option A is to reduce exposure to an industrial chemical that increases the risk for leukemia from 0.5 per 100,000/year to 2.0 per 100,000/year. It is estimated that 30% of the working population in the community is exposed to this agent. Option B is to reduce exposure to a different toxin that increases the risk for aplastic anemia from 0.5 per 100,000/year to 50 per 100,000/year. It ¡s estimated that 5% of the working population is exposed to this toxin. The estimated cost of each intervention is US $740,000. It is assumed that each intervention program will have similar effectiveness in eradicating the exposure. The case fatality rates are similar for both diseases. Which of the following is the best rationale for the health department to use in selecting an option?

A) Option A because more fatalities will be prevented

B) Option A because more workers are exposed to the toxic agent

C) Option B because more fatalities will be prevented

D) Option B because more workers are exposed to the toxic agent

E) The best approach cannot be determined based on the information provided

Dissecting the question

- This question targets the topic: Relative Risk [Relative risk is a high yield topic]

- The quick formula for Relative Risk for this purpose is to divide:

 Exposed group (or no treatment) / Unexposed group (or with treatment)

- What these kinds of questions ask, is for you to compare the risk of Option A relative to Option B.

- Every other information in the vignette isn’t needed to arrive at the answer.

- You can easily spot this type of question by looking for the keyword “Risk” when you are asked to compare one group to another (Just like the above question).

Solving for an answer:

From Option A (Risk for leukemia):

Exposed group = 2

Unexposed group = 0.5

Putting in the formula:

2/0.5 = 4% (Relative Risk of 4)

From Option B (Risk for aplastic anemia):

Exposed group = 50

Unexposed group = 0.5

Putting in the formula:

50/0.5 = 100% (Relative risk of 100)

So the Risk in Option B is 100% relative to that in Option A which is 4%. 

It means it would be better to invest in an intervention that would reduce the risk of disease by 100% than to invest in one that reduces the risk by only 4%.

The answer is "Option C) Option B because more fatalities would be prevented".

It is not “D) Option B because more workers are exposed to the toxic agent” because we are working with the risk increased per year in each option (i.e 100,000/yr), we are not working with the percentages of workers exposed to the agents. The reason is, even though 30% of workers are exposed to Option A’s agent the risk of getting leukemia is 4%. For Option B, only 5% of the working population is exposed to it, but the risk of getting aplastic anemia is 100% from the calculation.

Take home:

When you meet any biostat question that wants you to compare risk in one group to another,

- Remember relative risk

- Extract exposed numbers and unexposed numbers from the questions

- Divide E (exposed) with U (unexposed) [E/U = RR]

- The group with the highest number has the more risk and vice versa.

- Every other information from the vignette may not be helpful

- All the methods or assumptions in these questions might not be perfect but if you grasp the concept, you'll find it easy to answer similar questions.

Reference:
1. Topic: Relative Risk. Book: First Aid for the USMLE step 1 2019. Public Health Sciences/Biostatistics section.

1. Antibiotics

Antibiotics like amoxicillin, clindamycin, and trimethoprim can cause significant liver damage. Antibiotic treatments usually take 7 to 10 days, depending on the illness and the organism's reaction. However, if this time is extended, it may have negative repercussions for the liver.

2.Paracetamol

When we're in pain, it's one of the first remedies we reach for. Unfortunately, we often do not seek medical advice, which can be fatal. One of the most common causes of liver injury is self-medication.

3.Anti-inflammatories

These are also regularly used drugs. We infer any indications of muscular inflammation, even if it's only a headache.

4. Statins

These medications are used to keep blood cholesterol levels in check. As a result, the dose should be carefully monitored by a professional.vThey must measure and test their patients at regular intervals.

Symptoms of a swollen liver

1. Pain in the abdomen

2. Jaundice is a type of jaundice that occurs (yellowish tone in eyes and skin)

3. Urine that is dark in color

4. Irritated Skin

5. Irritable bowel syndrome

6. Sickness

Advice

The most essential thing to remember when it comes to avoiding liver problems caused by drugs is to never self-medicate; instead, see your doctor if you are experiencing any discomfort

Karl Landsteiner, an Austrian doctor, discovered that four distinct blood types existed in the early 1900s, and human blood was arranged into four prominent blood types during the decade. It is a reality that one's blood classification is necessary for safe transfusions during a crisis since a blood coordinate is important for these procedures. In addition, blood can have an impact on our well-being and our financial status, as some people believe. 

Logical realities and inquisitive hypotheses concerning type O blood have piqued my interest and I'm anticipating telling you about my findings.

1.Type O blood characteristics

Red blood cells have four basic blood classifications based on whether A and B antigens are present on the red cell membrane or antibodies to these antigens are present in the plasma. Although the presence and absence of the A and B antigens do not negate the existence of the Rh factor, the Rh factor may either be present or absent. Each of them describes an individual blood categorization from the top to the bottom: A+, A-, B+, B-, O+, O-, AB+, and AB. The red blood cells in Type O individuals don't have either A or B antigens but do have both A and B antibodies in the plasma. People of diverse ethnic and racial groups can be separated into groups by typing O+: this explains about 37% to 53% of all of them.

2.People with type O blood are blood donors who can give to anyone.

O+ blood donors can donate to all 4 groupings but only to those with the RH positive subgroup (O+, A+, B+, AB+). O-type red cells can be given to all eight categories, making it a widely-used blood classification. Type O-blood is given to patients in an emergency when the crossmatch test is not yet finished. O-blood is the safest for newborns whose underdeveloped insusceptible frameworks make them sensitive to the O-type. 

3.Type O blood can only be given to individuals with type O blood.

O+ individuals can acquire blood from both O+ and O-type individuals, but O-type individuals only have access to O-type blood. Type O blood is often swapped for type O+ blood in crises. It has numerous health benefits.

O-type persons have the least chance of developing coronary sickness compared to the other three blood types. Recent studies indicate that those who have non-O blood type are 25% more likely to have pancreatic malignant development than individuals with O blood type. People who have blood type O are also less likely to suffer from circulation difficulties and subjective issues. Whether or not that is the case, it is essential to preserve a sound way of life, along with keeping an eye on risk factors, to stay a healthy distance from illnesses, regardless of your blood type. 

Which blood type do you belong to? You should know that your blood type may affect many aspects of your life.

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