The ABCD2 score is a seven-point score for identifying patients who have suffered a transient ischemic attack (TIA) at the highest risk of stroke in the following 2-day period. Since its publication, the ABCD2 score has become widely used by front-line healthcare providers to risk stratify patients with TIA and determine how urgently these patients should be seen for subsequent assessment and treatment. While its c statistic is similar to those of the ABCD and California scores, the ABCD2 score has been more widely validated and has been shown to accurately predict the risk of stroke at 2, 7, and 90 days following a TIA. Some have criticized the ABCD2 score for only taking into account clinical features and not giving any consideration to investigations. Moreover, the score has been shown to be predictive of carotid embolic sources, but less useful for cardiac sources of emboli.
In-Depth Originally published in The Lancet in 2007, the purpose of this study was to develop a tool to identify patients at highest early risk of stroke following a TIA. The ABCD2 score was created by merging two previously validated clinical decision rules the ABCD and the California scores. The ABCD score was created to estimate the 7-day risk of stroke following a TIA, while the California score predicted the 90-day risk. The two scores shared many features, and were combined in hopes of developing a more widely validated model to identify patients at the highest risk of stroke 2 days after a TIA, thereby allowing clinicians to determine if patients required urgent management. Study cohorts were drawn from the Kaiser-Permanente Medical Care Plan in Northern California, United States and from Oxfordshire, United Kingdom. The c statistic was calculated to measure predictive ability. All combinations of factors from the ABCD and California scores were tested for their c statistic, and the combination with the highest statistic for 2-day risk of stroke was selected and validated. In total, the two derivation groups and four validation groups included 4,809 individuals with TIA. The new composite score was named the ABCD2 score, because it took into account age, blood pressure, clinical features, duration, and diabetes mellitus diagnoses.