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Zorluk: OrtaMeasures of Disease Frequency and Association

Physicians at a tertiary care center note an increased incidence of cholangiocarcinoma in their region. To investigate potential risk factors, they identify 5050 patients diagnosed with cholangiocarcinoma between 20152015 and 20252025. They then select 100100 patients treated at the same center for non-biliary conditions to serve as a comparison group. A review of electronic medical records reveals that 2020 of the patients with cholangiocarcinoma and 1010 of the comparison patients have a documented history of primary sclerosing cholangitis (PSC).

Based on this study design, which of the following is the most appropriate measure of association and its calculated value?

  1. A
    Odds ratio of 4.04.0
  2. B
    Relative risk of 6.06.0
  3. C
    Attributable risk of 0.300.30
  4. Odds ratio of 6.06.0Cevap
  5. E
    Relative risk of 4.04.0

Cevap

Odds ratio of 6.06.0
The correct answer accurately identifies that selecting patients based on disease status defines a case-control study, which requires calculating an Odds Ratio (OR). The OR compares the odds of exposure among cases to the odds of exposure among controls. In this scenario, the odds of having PSC among cases is 20/3020/30, and the odds among controls is 10/9010/90. Dividing these yields 20/3010/90=6.0\frac{20/30}{10/90} = 6.0.

Adım Adım Çözüm

1
Identify the study design based on participant selection methodology.
The investigators selected patients based on their outcome (cholangiocarcinoma vs. non-biliary conditions). This confirms a case-control study design.
Study design determines which epidemiological measures can be validly calculated.
2
Select the appropriate measure of association for a case-control study.
The Odds Ratio (OR) is the correct measure.
Case-control studies cannot establish disease incidence, meaning Relative Risk (RR) and Attributable Risk (AR) cannot be directly calculated.
3
Extract the data into a 2x2 contingency format.
Cases (Total = 50): Exposed = 20, Unexposed = 30. Controls (Total = 100): Exposed = 10, Unexposed = 90.
Organizing data correctly is essential to calculate the odds.
4
Calculate the Odds Ratio using the formula: OR = (Odds of exposure in cases) / (Odds of exposure in controls).
OR = (20 / 30) / (10 / 90) = (2/3) / (1/9) = (2/3) * (9/1) = 18 / 3 = 6.0.
This yields the correct final measure of association.

Anahtar Kavram

Identifying a case-control study design and properly calculating the Odds Ratio.
Tahmini Süre:1m 15s
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Konular

Measures of Disease Frequency and Association

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