Base rates of postconcussion syndrome by method of symptom report.

This study compared the base rate of postconcussion syndrome (PCS) symptoms using three different assessment methods in a nonclinical sample. Seventy-three university students with no history of brain injury or neurological disease reported symptoms experienced during the previous 2 weeks in response to an open-ended question, a structured interview (simulated), and the British Columbia Postconcussion Symptom Inventory (BC-PSI). Statistically significant differences (all p < .001, d = 1.80-3.93, large effect sizes) were found between the number of symptoms reported on all assessment methods, such that participants reported the most PCS symptoms on the BC-PSI (M = 9.45, SD = 2.52), followed by the structured interview (M = 5.58, SD = 2.02), and the open-ended question (M = 1.86, SD = 1.00). Further, 100%, 92.1%, and 25.4% of the sample reported three or more ICD-10 Category C PCS symptoms on the BC-PSI, structured interview, and open-ended question, respectively. Findings suggest that method of assessment influences PCS base rates, such that symptom elicitation decreases relative to the reduction in prompting associated with each assessment method. Therefore, different diagnostic conclusions may be drawn depending on method of assessment used. Clinicians need to consider how their chosen assessment method may be influencing the symptoms reported by their patients.