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Difficulty: MediumEpidemiologic Study Designs

Sports medicine physicians aim to determine if early sports specialization increases the risk of ulnar collateral ligament (UCL) tears. They query a regional network database spanning the last decade. The physicians identify 200200 adolescent baseball pitchers who underwent surgical reconstruction for a UCL tear. For a comparison group, they randomly select 600600 adolescent baseball pitchers from the same database who were treated for acute, non-throwing contact injuries during the same period. The physicians then review the patients' initial intake questionnaires and conduct structured telephone interviews to determine how many athletes in each group specialized exclusively in pitching before the age of 1212. Which of the following is the most appropriate measure of association to report for this investigation?

  1. Odds ratioAnswer
  2. B
    Relative risk
  3. C
    Attributable risk
  4. D
    Prevalence ratio
  5. E
    Hazard ratio

Answer

Odds ratio
The scenario describes a case-control study. The participants were initially selected based on the presence of the disease outcome (UCL tears) or the absence of the disease outcome (contact injuries). Once the groups were established, the researchers evaluated their past history to ascertain exposure status (sports specialization before age 1212). In a case-control design, the investigator artificially determines the number of controls for each case (in this scenario, a 3:13:1 ratio). Because the study population does not represent the natural population at risk, the true incidence of the disease cannot be measured. Consequently, incidence-based metrics such as relative risk and attributable risk cannot be calculated. Instead, the odds ratio must be used to estimate the association between the exposure and the outcome.

Step-by-Step Solution

1
Identify the sampling strategy used by the investigators.
Participants were selected based on the presence (UCL tear) or absence (contact injuries) of the outcome.
Determining how participants are enrolled is the key to identifying the study design.
2
Determine the temporal direction of the study.
After selecting the groups based on the outcome, the investigators looked backward in time to ascertain past exposure (early specialization).
Looking backward from outcome to exposure confirms the design as a case-control study.
3
Match the study design to the appropriate statistical measure.
Case-control studies use the odds ratio.
Because investigators artificially set the number of controls per case, true disease incidence cannot be measured, meaning risk-based measures (like relative risk) cannot be calculated directly.

Key Concept

Case-control studies select participants based on disease status and retrospectively assess exposure. Because they cannot measure incidence, the odds ratio is the appropriate measure of association.
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Epidemiologic Study Designs

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