Assessment and Classification
What this domain tests
This domain tests the mental state examination, the logic of classification systems (DSM-5-TR, ICD-11), and the psychometrics of screening and diagnostic tests. Expect questions on what a score does and does not mean.
Core rules and concepts
- MSE domains: appearance and behaviour, speech, mood and affect, thought form and content, perception, cognition, insight, judgement, risk.
- Classification: both systems remain predominantly categorical. ICD-11 includes complex PTSD, prolonged grief disorder, and a fully dimensional personality disorder model (severity plus five trait domains, with a borderline pattern qualifier). DSM-5-TR added prolonged grief disorder and retains the ten personality disorder categories plus the Section III alternative model.
- Psychometrics: sensitivity = true positives among the ill; specificity = true negatives among the well. Positive predictive value falls steeply as prevalence falls, so a good test used in a low-prevalence setting generates many false positives.
- Reliability: kappa above 0.8 is excellent, 0.6–0.8 good.
- Instruments: PHQ-9 and GAD-7 measure severity, not diagnosis; AUDIT screens alcohol; CIWA-Ar guides withdrawal; MMSE and MoCA screen cognition; PANSS, MADRS and YMRS measure severity in trials.
Worked example
A screen has 90% sensitivity and 90% specificity and is applied where prevalence is 1%. In 10,000 people, 100 are ill: 90 are detected and 10 missed; of 9,900 well people, 891 are falsely positive. PPV is 90/981, about 9%. Most positives are wrong, which is why screening precedes, but never replaces, diagnostic assessment.
Traps that cost marks
- Treating a screening score as a diagnosis.
- Confusing incidence (new cases) with prevalence (existing cases).
- Assuming DSM-5-TR and ICD-11 are interchangeable; they differ on complex PTSD, personality disorder structure and some durations.