Diagnosis of TIA (DOT) score – design and validation of a new clinical diagnostic tool for transient ischaemic attack
Dutta BMC Neurology
Diagnosis of TIA (DOT) score - design and validation of a new clinical diagnostic tool for transient ischaemic attack
Dipankar Dutta 0
0 Stroke Service, Gloucestershire Royal Hospital , Great Western Road, Gloucester GL1 3NN , UK
Background: The diagnosis of Transient Ischaemic Attack (TIA) can be difficult and 50-60 % of patients seen in TIA clinics turn out to be mimics. Many of these mimics have high ABCD2 scores and fill urgent TIA clinic slots inappropriately. A TIA diagnostic tool may help non-specialists make the diagnosis with greater accuracy and improve TIA clinic triage. The only available diagnostic score (Dawson et al) is limited in scope and not widely used. The Diagnosis of TIA (DOT) Score is a new and internally validated web and mobile app based diagnostic tool which encompasses both brain and retinal TIA. Methods: The score was derived retrospectively from a single centre TIA clinic database using stepwise logistic regression by backwards elimination to find the best model. An optimum cutpoint was obtained for the score. The derivation and validation cohorts were separate samples drawn from the years 2010/12 and 2013 respectively. Receiver Operating Characteristic (ROC) curves and area under the curve (AUC) were calculated and the diagnostic accuracy of DOT was compared to the Dawson score. A web and smartphone calculator were designed subsequently. Results: The derivation cohort had 879 patients and the validation cohort 525. The final model had seventeen predictors and had an AUC of 0.91 (95 % CI: 0.89-0.93). When tested on the validation cohort, the AUC for DOTS was 0.89 (0.86-0.92) while that of the Dawson score was 0.77 (0.73-0.81). The sensitivity and specificity of the DOT score were 89 % (CI: 84 %-93 %) and 76 % (70 %-81 %) respectively while those of the Dawson score were 83 % (78 %-88 %) and 51 % (45 %-57 %). Other diagnostic accuracy measures (DOT vs. Dawson) include positive predictive values (75 % vs. 58 %), negative predictive values (89 % vs. 79 %), positive likelihood ratios (3.67 vs. 1.70) and negative likelihood ratios (0.15 vs. 0.32). Conclusion: The DOT score shows promise as a diagnostic tool for TIA and requires independent external validation before it can be widely used. It could potentially improve the triage of patients assessed for suspected TIA.
Transient ischaemic attack; Diagnosis; Diagnostic score; Logistic regression
Background
The diagnosis of transient ischaemic attack (TIA) can
be difficult and studies show limited inter-observer
agreement for clinical diagnosis [
1
]. About 50 to 60 %
of TIA referrals by non- specialists turn out to be
noncerebrovascular mimics [
2–4
]. Patients with TIA have a
high risk of early stroke and subsequent adverse events
[
5, 6
]. Following secondary prevention studies [
7, 8
]
and the introduction of the ABCD2 score [
9
], rapid
assessment TIA clinics have been set up to investigate
and manage TIA. Inappropriate referrals to TIA clinics,
however, can lead to delays for patients with TIA and
the misdiagnosis of non -cerebrovascular conditions as
TIA leads to unnecessary anxiety and inappropriate
initial management.
Stroke diagnostic tools such as FAST and ROSIER
have been developed for use by pre hospital assessors
and emergency room clinicians [
10, 11
]. The ABCD2
score, too, has been used as a crude diagnostic aid for
TIA [12]. More recently, the ability of the ABCD2 score
to reliably discriminate between those at high or low risk
after a TIA has been called into question and a third of
mimics found to have ABCD2 scores ≥ 4 [
13
]. A TIA
diagnostic tool could be used to improve TIA clinic
triage by removing some mimics from urgent TIA
pathways. There is only one TIA diagnostic tool, the score of
Dawson and colleagues [
14
] which was not designed for
retinal and some posterior circulation events and is not
widely used. It has shown limited accuracy when used in
a primary care setting [
15
]. The Diagnosis of TIA Score
(DOTS) is a new tool to help non-specialists make the
diagnosis of TIA with greater accuracy. It includes
retinal and posterior circulation events and is meant for
use as a mobile app and web based calculator.
Methods
Development cohort
The development cohort for the score was a subset of
TIA clinic patients studied retrospectively from a TIA
database [
2
]. Briefly, all patients referred to the Monday
to Friday TIA clinics of Gloucestershire Royal Hospital
(GRH), Gloucester, UK between April 2010 and May
2012 were eligible for inclusion in the development
cohort. The catchment area for GRH has a population of
560,000. Referrals are accepted from Emergency
Departments, General Practitioners, paramedics and other
departments such as ophthalmology.
Data collected included demographic information, past
medical history, a detailed history, examination findings,
ABCD2 scores, results of investigations (blood tests,
ECG, same day carotid duplex ultrasounds, same day (...truncated)