In our present study, we found that diastolic blood pressure, the score of ABCD3-I and DOT were independently associated with the occurrence of definite cerebrovascular events. Besides, DOT score also performed relatively good calibration and discrimination, with the greatest area under the ROC curve.
The definition of TIA has been changing with the development of advanced techniques of neuroimaging. TIA was classically defined as a focal cerebral ischemic event with symptoms lasting <24 hours. Due to the rapid development of neuroimaging, up to one-third of patients with TIA may have radiological evidence of acute infarction [18, 19]. The frequency of positive DWI findings varied from 9 to 67% among different cohorts of patients with TIA [8, 20, 21]. Therefore, the definition of TIA is moving from “time-based TIA” to “tissue-based TIA” as “a transient episode of neurological dysfunction caused by focal brain, spinal cord, or retinal ischemia, without acute infarction” [17]. Changing the definition of TIA from time to a tissue basis could produce a landmark of the development and progress of stroke.
TIA requires urgent investigation and it has been poorly managed in many sites. The term of ‘transient neurological symptoms’ is used to describe the broad spectrum of symptoms following TIA or TIA mimics. Unilateral weakness and speech disturbances are the most common manifestations of TIA [22]. It was reported unilateral weakness and speech disturbance were found in approximately 31%-54% and 25%-42% of TIA, respectively [18]. There is no gold standard clinical tool used to diagnose a TIA or stroke based on symptomology, however, the diagnosis of TIA needs the assessment of symptoms and adequate evaluation by a stroke specialist. However, accurate identification of stroke and TIA patients is quite difficult. It was reported up to 50% to 60% of TIA patients were diagnosed to be noncerebrovascular mimics by non-specialists [23]. Another report showed that 35% of referrals to TIA clinics were nonvascular mimics [24]. As a result, it is vital and valuable that the differential diagnosis of transient neurological symptoms including both patients with TIA and mimics (e.g. migraine or seizure) [25, 26].
In spite that MRI may be a very useful tool and certainly reduces the rate of false-negative diagnoses, it still cannot replace clinical assessment, especially for those patients with MRI-negative. As a result, the clinical evaluation could be quite important to stratify different risk factors of TIA patients. Risk stratification instruments such as the scores of ABCD scores series (such as ABCD, ABCD2, ABCD3, ABCD3-I) could be available but were developed on populations with confirmed TIA. The ABCD2 scores which were recorded by the referring clinician, showed very poor discrimination for the diagnosis of TIA [27]. To date, the ABCD3-I scores has been considered to be the best validated and predominantly used risk evaluators in TIA patients [28, 29]. However, due to the fact that MRI is not available in all healthcare settings and medical emergency, ABCD3-I scores could also have some limits in our clinical practice.
A TIA diagnostic tool could be utilized to improve TIA clinic triage by differentiating some TIA mimics from urgent TIA pathways. To date, there have been only two diagnostic algorithms for the early diagnosis of TIA. The clinical scoring system of Dawson was proved to facilitate accurate detection of TIA. However, it was limited to use in a primary care setting and not involving the retinal and posterior circulation cerebrovascular events [14]. The second one was the DOT score, which was considered to be a new tool for non-specialists to make the diagnosis of TIA with greater accuracy [15]. However, this new tool of DOT has not yet been externally validated in other populations out of the United Kingdom. Our findings indicated that DOT score performed relatively good calibration and discrimination, with a sensitivity of 70.3% and specificity of 62.9%, respectively. We also found that DOT performed the greatest area under the ROC curve, and ABCD3-I ranked the second greatest area. According to Dutta D study in 2016, the AUC for DOT was 0.89 and Dawson score was 0.77, while ABCD2 was 0.64. In spite that our data were not as perfect as Dutta D study, however, our findings were consistent with it. It was reported that the AUC of ABCD2 score and ABCD3-I score was 0.50 and 0.58 in South Korea population [30]. In the population of Spain, the area under the ROC curve of ABCD2 and ABCD3-I for ischemic events prediction were 0.49 and 0.77 [31]. Recently, the ABCD3-I score performed equally in TIA patients in tissue- as well as time-based definition and the same for minor stroke patients [22]. Our study was also in line with the above studies.
Our study had some limitations which should be raised. Firstly, this study was designed as a retrospective study from a single center, which was a great disadvantage. Studies with a larger numbers from multiple centers in China are needed urgently to further confirm our findings. Secondly, we did not perform follow-ups to assess of the risk factors of the recurrence of TIA or stroke, and not get the time from symptom onset to DWI examination (time-to-DWI). The above issues may be also great importance for the assessment and management of TIA. Thirdly, our study also lacked of stratification such as low, median, high subgroup according to ABCD2/ABCD3-I scores; and we did not perform the etiological classification of stroke/TIA, according to the Trial of Org 10172 in Acute Stroke Treatment. Fourthly, we did not find blood or imaging biomarkers available to reliably distinguish TIA from TIA-mimics [32]. Despite these limitations, as far as we know, the present study is the largest ever-reported study to identify the clinical predictors for the diagnosis of TIA. Besides, for the first time, we have externally validated the DOT score as for a new tool of TIA in patients with TIA in China. Thirdly, we further conformed that the score of DOT could encompass the entire spectrum of TIA/stroke, which could be used as a mobile app and web based calculator with more accurate to assess.