External validation of the Post-Concussion Symptoms (PoCS) Rule for predicting mild traumatic brain injury outcome.

Persistent symptoms are common after a mTBI. The Post-Concussion Symptoms (PoCS) Rule is a newly developed clinical decision rule for the prediction of persistent post-concussion symptoms (PPCS) 3 months after a mTBI. The PoCS Rule includes assessment of demographic and clinical characteristics and headache presence in the Emergency Department (ED), and follow-up assessment of symptoms at 7 days post-injury using two thresholds (lower/higher) for symptom scoring. We examined the PoCS Rule in an independent sample. We analyzed a clinical trial that recruited participants with mTBI from EDs in Greater Vancouver, Canada. The primary analysis used data from 236 participants, who were randomized to a usual care control group, and completed the Rivermead Postconcussion Symptoms Questionnaire at 3-months. The primary outcome was PPCS, as defined by the PoCS authors. We assessed the overall performance of the PoCS rule (area under the receiver operating characteristic curve, AUC), sensitivity and specificity. Over 40% of participants (median age=38 years, 59% female) reported PPCS at 3 months. Most participants (88%) were categorized as medium risk based on the ED assessment, and a majority were high risk according to the final PoCS Rule (81% using a lower threshold and 72% using a higher threshold). The PoCS Rule showed sensitivity of 93% (95% CI, 88-98; lower threshold) and 85% (95% CI, 78-92; higher threshold), and specificity of 28% (95% CI, 21- 36) and 37% (95% CI, 29-46), respectively. The overall performance was modest (AUC 0.61, 95% CI 0.59, 0.65). In conclusion, the PoCS Rule was sensitive for PPCS, but had a low specificity in our sample. Follow-up assessment of symptoms can improve risk stratification after mTBI.