In this cohort drawn from a large integrated health care program in 1997-8, neurology consultation for TIA was uncommon overall (28%) and in-person consultation was rare (4% overall). Previous studies that captured only in-person consultations rather than telephone consultations and have reported rates ranging from 8% in a cohort of TIA and stroke patients in an urban ED20
to 29% of TIA patients in a rural ED that would otherwise be considered neurologically underserved.21
Our analysis reflects practice patterns that existed before the risks of stroke after TIA were more widely appreciated, but more recent data reflecting current practice for consultation for TIA has not been widely reported.
The decision to consult a neurologist from the ED is a complex one. We did find that patients who were at higher risk for stroke were not the ones who were targeted for urgent neurological evaluation; indeed there was no relationship between a higher risk of stroke as predicted by the ABCD2 score and more frequent urgent neurology consultation. This finding underscores the potential value of this prognostic tool to help guide clinical decision-making in current practice because reliable and validated methods for identifying high-risk TIA patients were not available during the study period.
Instead, the decision about whether to obtain a neurology consultation from the ED appeared to rely on other factors that were independent of risk. Such factors may include institutional norms and local practice patterns, the availability of an on-call neurologist, and the perceived value-added by a consultation in the acute setting. Other factors might include clinical uncertainty rather than acuity since patients who were perceived to be low-risk, but where the diagnosis was uncertain may have targeted for consultation (e.g. patients with migraine on the differential diagnosis). But our cohort was limited to only those patients who had a final ED diagnosis of TIA. Alternatively, certain higher-risk patients may have been targeted for consultation only if management was uncertain. For instance, patients who were already taking aspirin were more likely to have consultations (e.g. patients having possible vascular events while on antiplatelet therapy [“aspirin-failures”]). ED clinicians could have been seeking advice on alternative antithrombotic therapy for these patients. The racial and sex disparities in consultation requests that we observed were more difficult to explain, though they parallel previously described disparities in referral patterns and inpatient treatment of TIA22
and for stroke23, 24
and merit further study. These comparisons of baseline characteristics by consultation status are exploratory in nature and may represent hypotheses for future study.
Given the lack of a clear association between patient acuity and consultation, it is not unexpected that we found only weak associations between consultation and improved process of care measures for TIA. The main areas of associated improvements were in more frequent use of antiplatelet and anticoagulation therapy and in higher rates of hospital admission, both of which have the potential to impact patient outcomes. Our study is unable to distinguish between whether the decision to prescribe antithrombotics or to admit the patient was made prior to consultation or as a consequence of consultation. But these associations did not appear to be simply a marker for more intensive management for consultation patients generally. Although utilization of diagnostic testing for patients with TIA overall may be different today, we found no clear association between consultation and the use of brain imaging, ECGs, and carotid ultrasound, or on the use of anticoagulation for cases of atrial fibrillation, which was comparable to nationally reported rates.26
To the extent that utilization of diagnostic testing is a process measure that may be important for improvement in outcomes, this finding would be expected to attenuate any observed differences in outcomes by consultation status.
Previous studies examining the impact of neurologists have largely focused on stroke rather than TIA. Here the evidence has been conflicting. Some studies have suggested that timely neurological attention is associated with better outcomes13-17
and shorter hospitalizations.25
However, a more recent analysis that accounted for differences in the initial prognosis for patients treated by neurologists versus internists has brought some of these conclusions into question.12
These studies highlight the difficulty of identifying an independent effect of neurologists on clinical outcomes within the milieu of heterogeneous practice patterns.
Given that the ABCD2 score was similar in the two groups, one would expect that the observed incidence of subsequent stroke would also be similar. In fact we found that during the first week, when the risk for stroke after TIA is highest, the probability of stroke and of adverse outcomes was lower for consultation patients. But by 90 days, although we observed a 1.1% lower absolute incidence of stroke and a 2% lower absolute incidence of adverse events with consultation, the overall magnitude of this difference was smaller as compared to the initial period and did not meet statistical significance. The heterogeneous nature of neurology consultation, particularly during the study period when there was less consensus on optimal management, as well as the additional impacts of subsequent inpatient and outpatient management decisions would both serve to dilute the potential impact of consultation on longer-term outcomes.
Several limitations of our study are important to consider in interpreting these findings. First, consultations were obtained in the period before the urgent risks of TIA were widely appreciated and before there was a greater consensus on optimal management of TIA. Also practice patterns in a large integrated health care program may not reflect current practice in other clinical settings. Both of these factors limit generalizability to current practice. Second, since our analysis was focused only on urgent neurology consultations from the ED, in-patient neurology consultations that took place after hospital admission or in follow-up were not captured. This effective “crossover” of patients from the no consultation to the consultation group could lead to an underestimation of the impact of consultation and could explain the discrepancy between the one-week and the 90-day outcomes that was observed. Third, important prognostic differences between the two groups that influenced the decision on consultation may not have been captured, particularly since patients who had a neurology consultation and were not given the final diagnosis of TIA would not be captured in our cohort. The important potential role of neurologists in helping to identify patients who did not
have a TIA cannot be addressed with the current study. Potential for confounding by indication akin to that encountered in similar studies of stroke patients is possible as well,12
though we attempted to mitigate the effects of prognostic differences in the groups by using the validated ABCD2
score. Nonetheless, other unmeasured confounders may limit the validity of inferences drawn from our analysis. Fourth, the specific content of the consultation and the changes in management that are directly attributable to the neurology consultation was not available. Finally, as a secondary analysis and an observational study, multiple comparisons and subgroup analysis may limit interpretation of our findings beyond hypothesis-generating exploratory analysis.
In summary, we found that during a period before the widespread appreciation of the risks of stroke after TIA, urgent neurology consultation was not targeted to patients who were at highest-risk for stroke. Although we found that urgent neurology consultation was associated with modest improvements early patient outcomes, these associations did not persist at 90 days. Here we present a snapshot and exploratory analysis of previous practice patterns that may form the basis for comparisons to current practice and may serve to highlight the importance of determining the particular processes of care that have the most impact on clinical outcomes. Current practice in terms of diagnostic testing, neurology consultation, and use of antithrombotic medications is likely to have changed and it is possible that neurology consultation may be more valuable today with a greater consensus on the optimal acute management of TIA,27-29
a greater recognition of the impact of aggressive early interventions,3,4
and an emphasis on developing specific quality measures by health care funding agencies, accreditation organizations, and professional groups.30