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Zorluk: OrtaMeasures of Disease Frequency and Association

Researchers at an academic medical center are evaluating the long-term safety profile of a newly approved Janus kinase (JAK) inhibitor for refractory rheumatoid arthritis. They conduct a prospective cohort study comparing patients prescribed the new JAK inhibitor to patients receiving a standard tumor necrosis factor-alpha (TNF-α) inhibitor. All patients are followed for 5 years to monitor for adverse cardiovascular events, specifically deep vein thrombosis (DVT).

The results of the study are summarized in the table below:

Medication GroupTotal PatientsPatients Developing DVT
JAK Inhibitor2,0002,000100100
TNF-α Inhibitor3,0003,0006060

Based on the data provided, which of the following represents the percentage of DVT cases among patients taking the JAK inhibitor that can be attributed to the medication itself rather than background risk?

  1. A
    3%3\%
  2. B
    33%33\%
  3. C
    40%40\%
  4. 60%60\%Cevap
  5. E
    250%250\%

Cevap

The correct percentage of DVT cases attributable to the JAK inhibitor is 60%.
The question asks for the Attributable Risk Percent (ARP), which represents the proportion of disease in the exposed group that is directly attributable to the exposure. It is calculated using the formula: ARP=Incidenceexposed−IncidenceunexposedIncidenceexposedARP = \frac{Incidence_{exposed} - Incidence_{unexposed}}{Incidence_{exposed}}. First, determine the incidence in the exposed (JAK inhibitor) group: 100/2,000=0.05100 / 2,000 = 0.05. Next, determine the incidence in the unexposed (TNF-α inhibitor) group: 60/3,000=0.0260 / 3,000 = 0.02. Finally, apply the formula: ARP=0.05−0.020.05=0.030.05=0.60ARP = \frac{0.05 - 0.02}{0.05} = \frac{0.03}{0.05} = 0.60, which is 60%60\%.

Adım Adım Çözüm

1
Calculate the incidence of DVT in the exposed group (JAK inhibitor).
Iexposed=1002,000=0.05I_{exposed} = \frac{100}{2,000} = 0.05 (or 5%5\%).
This establishes the total risk of developing the outcome for patients taking the new medication.
2
Calculate the incidence of DVT in the unexposed group (TNF-α inhibitor).
Iunexposed=603,000=0.02I_{unexposed} = \frac{60}{3,000} = 0.02 (or 2%2\%).
This establishes the baseline or background risk of the outcome in this specific patient population.
3
Identify the requested epidemiological metric.
The question asks for the "percentage of DVT cases among patients taking the JAK inhibitor that can be attributed to the medication." This is the Attributable Risk Percent (ARP).
Translating the clinical question into the correct biostatistical formula is necessary to select the right calculation.
4
Calculate the Attributable Risk Percent (ARP).
ARP=Iexposed−IunexposedIexposed×100=0.05−0.020.05×100=0.030.05×100=60%ARP = \frac{I_{exposed} - I_{unexposed}}{I_{exposed}} \times 100 = \frac{0.05 - 0.02}{0.05} \times 100 = \frac{0.03}{0.05} \times 100 = 60\%.
This formula isolates the excess risk caused by the exposure and divides it by the total risk in the exposed group to yield the attributable fraction.

Anahtar Kavram

Attributable Risk Percent (ARP) calculation and interpretation
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Konular

Measures of Disease Frequency and Association

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