Background: To determine the psychometric characteristics of diagnostic justification scores based on the patient note format of the United States Medical Licensing Examination Step 2 Clinical Skills exam, which requires students to document history and physical findings, differential diagnoses, diagnostic justification, and plan for immediate workup.
Method: End-of-third-year medical students at one institution wrote notes for five standardized patient cases in May 2013 (n = 180) and 2014 (n = 177). Each case was scored using a four-point rubric to rate each of the four note components. Descriptive statistics and item analyses were computed and a generalizability study done.
Results: Across cases, 10% to 48% provided no diagnostic justification or had several missing or incorrect links between history and physical findings and diagnoses. The average intercase correlation for justification scores ranged from 0.06 to 0.16; internal consistency reliability of justification scores (coefficient alpha across cases) was 0.38. Overall, justification scores had the highest mean item discrimination across cases. The generalizability study showed that person-case interaction (12%) and task-case interaction (13%) had the largest variance components, indicating substantial case specificity.
Conclusions: The diagnostic justification task provides unique information about student achievement and curricular gaps. Students struggled to correctly justify their diagnoses; performance was highly case specific. Diagnostic justification was the most discriminating element of the patient note and had the greatest variability in student performance across cases. The curriculum should provide a wide range of clinical cases and emphasize recognition and interpretation of clinically discriminating findings to promote the development of clinical reasoning skills.