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Criterion validity — MRCPsych Paper A MCQ

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HardEpidemiology and research methodsCriterion validityMRCPsych Paper A

A 12-item self-report depression scale is evaluated in 400 psychiatric outpatients. It has a Cronbach's alpha of 0.91 and produces similar scores when repeated after 2 weeks in clinically stable participants. In a separate analysis, a prespecified cut-off is compared with an independent, blinded structured clinical interview for major depressive disorder conducted at the same visit; sensitivity, specificity and the area under the receiver operating characteristic curve are calculated. Which measurement property is assessed by this separate analysis?

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Correct answer: A — Criterion validity

Explanation lettering: D = shown as A · A = shown as B · B = shown as C · C = shown as D

D is correct. Criterion validity concerns how well an instrument agrees with an external reference criterion. Here, the depression-scale cut-off is compared with an independent structured diagnostic interview, and diagnostic performance is quantified using sensitivity, specificity and ROC area. Because both assessments occur at the same visit, this is specifically concurrent criterion validity. Internal consistency is the extent to which scale items measure the same underlying construct and is represented by Cronbach's alpha. Test-retest reliability is score stability over time and is represented by the repeated assessment after 2 weeks. Inter-rater reliability concerns agreement between different observers rating the same phenomenon; the stem does not compare interviewers. Face validity is a subjective judgement that an instrument appears to measure depression and is not established through reference-standard diagnostic accuracy analysis.

Reference: Hammer EM et al. Validity of the ALS-Depression-Inventory (ADI-12)—a new screening instrument for depressive disorders in patients with amyotrophic lateral sclerosis. Journal of Affective Disorders. 2008;109:213-219. https://pubmed.ncbi.nlm.nih.gov/18262283/