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Zorluk: ZorMeasures of Disease Frequency and Association

An investigator is studying the association between occupational exposure to a specific organic solvent and the subsequent development of peripheral neuropathy. The investigator queries a large manufacturing plant's employee database spanning the past 20 years.

The study population is identified and grouped based on whether their documented job classification during their first year of employment involved direct handling of the organic solvent. The investigator then reviews the occupational health and medical records of these employees from their first year of employment up to the present day to determine the incidence of peripheral neuropathy in both groups.

The findings are summarized in the table below:

Exposure StatusPeripheral NeuropathyNo Peripheral NeuropathyTotal
Solvent Exposed1508501,000
Not Exposed2003,8004,000

Based on the study design, which of the following represents the most appropriate primary measure of association and its correctly calculated value?

  1. Relative risk of 3.0Cevap
  2. B
    Odds ratio of 3.4
  3. C
    Relative risk of 3.4
  4. D
    Odds ratio of 3.0
  5. E
    Absolute risk reduction of 10%

Cevap

The most appropriate primary measure of association is a relative risk of 3.0.
The correct answer indicates a relative risk of 3.0. This study is a retrospective cohort study because the investigator identifies the groups based on their past exposure status (job classification involving organic solvent) and then follows their records forward in time to the present to determine the outcome (peripheral neuropathy). In a cohort study, the primary measure of association is the relative risk (RR), which compares the incidence of disease in the exposed group to the incidence in the unexposed group. The incidence in the exposed group is 150/1,000=0.15150 / 1,000 = 0.15. The incidence in the unexposed group is 200/4,000=0.05200 / 4,000 = 0.05. Therefore, the relative risk is calculated as 0.15/0.05=3.00.15 / 0.05 = 3.0.

Adım Adım Çözüm

1
Identify the study design based on subject selection criteria.
The study groups patients by past exposure (solvent vs. no solvent) and follows them to the present to assess the outcome (neuropathy), indicating a retrospective cohort study.
Determining the study design is essential to select the correct measure of association.
2
Select the appropriate measure of association.
For a cohort study, the primary measure of association is Relative Risk (RR).
Cohort studies can directly measure true incidence, allowing for the calculation of RR. Odds Ratios (OR) are primarily used for case-control studies where incidence cannot be determined.
3
Calculate the incidence of the outcome in both groups.
Exposed incidence = 150 / 1,000 = 0.15. Unexposed incidence = 200 / 4,000 = 0.05.
These incidences are required to mathematically calculate the relative risk.
4
Calculate the Relative Risk.
RR = 0.15 / 0.05 = 3.0.
RR is the ratio of the incidence in the exposed group to the incidence in the unexposed group.

Anahtar Kavram

Identifying a retrospective cohort study and calculating the relative risk.
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Konular

Measures of Disease Frequency and Association

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