Assessment of Explicitly Stated Interval Change on Noncontrast Head CT Radiology Reports

Discussion

The American College of Radiology Practice Parameters recommends that every report should include comparison with prior examinations when available and appropriate as part of the radiologic consultation.¹ In this study, we found variable IC reporting mentioned in 67.3% of noncontrast head CT report findings with a prior examination. Whether IC was explicitly stated depended on multiple factors, including categorization of findings, chronicity of findings, and time interval between studies.

Finding categorization revealed variable application of IC. Typically, “acute” categories such as hemorrhage (95.3%), infarct/ischemia (76.8%), and mass effect (82.1%) had significantly higher but not perfect IC reporting. Hemorrhage and mass effect were more likely to have explicit IC mentioned in the impression, an appropriate approach given the acute clinical significance of any change in these findings. Intracranial mass also had high IC reporting (92.9%), which may be important for tumor monitoring and treatment planning.⁶ Most interesting, IC for intracranial mass was less likely to be in the impression; on a noncontrast head CT with probable advance imaging follow-up, IC of a mass may be less important than having the mass. The rate of IC reporting of pneumocephalus was only 71.4% and not significantly different from the rate for all findings, a concerning result given that pneumocephalus can be a potentially serious finding.⁷ The rate of explicit IC of ischemia/infarction (76.8%) and postprocedural (69.7%) and ventricular caliber (72.8%) IC reporting for these categories was not significantly different from all findings, likely representing a combination of “important” (acute hydrocephalus) and “secondary” (ex vacuo dilation) findings as determined by the reading radiologist.⁸

Stereotypically chronic (microvascular, 50.9%; volume loss, 47.1%) or typically “secondary” (sinus, 43.7%; soft-tissue/osseous, 36.4%) categories were less likely to have an explicitly stated IC. Given the relative ambiguity of the American College of Radiology recommendations, exclusion of these findings is likely appropriate.^2,8 However, in certain clinical settings, these findings, even chronic white matter microvascular ischemic changes,^9,10 may be relevant to patient care. Furthermore, the ordering provider may consider a certain diagnosis more important than a radiologist does. For example, prior studies have noted inconsistent reporting of the sinuses on CT with associated dissatisfaction among otolaryngologists.^11,12 Although it is likely appropriate to not mention IC for these typically chronic and “secondary” findings, careful examination of the study indication and patient presentation should always be considered before excluding IC.⁸

The higher rate of explicitly stated IC was significantly associated with the time interval between reports being <31 days (P < .001). Mention of IC may be important even if the interval time is >1 month. For example, conservative management of intracranial vascular abnormalities or surveillance after treatment may require prolonged observation and interval follow-up.^13⇓–15 Similarly, chronic findings were less likely to have explicitly stated IC (P < .001). However, monitoring chronic findings for long periods may have clinical significance. For example, longitudinal volume loss is important in predicting risk and clinical outcomes in different types of dementia.^16⇓–18

Structured reporting with clear terminology may improve the reporting of IC as well as the clinical utility of radiology reports. When IC was stated in our study, it was in ambiguous terms 7.5% of the time. Clear and standardized radiographic terminology may decrease confusion and make comparison with prior examinations easier.^6,19 For our retrospective review, both structured and narrative reports were reviewed with no standardization of IC. Currently, our institution uses structured reports nearly exclusively, though IC is not included. The use of a generalized statement increased the likelihood of IC reporting in our study (P < .001), and in certain respects, it may be considered a proxy for standardization. Structured radiology reports may result in improved understanding of radiographic findings and clinical utility compared with narrative reports.^{2,6,20⇓–22} Furthermore, studies have shown that clinicians may prefer standardized reports to narrative findings.^6,20,21,23 In addition, important features are less likely to be missed on structured reports.^20,21

Given our findings of overall poor reporting of IC, the higher percentage of reporting with generalized IC statements, and the literature regarding structured reporting, we propose including IC as a part of the standardized radiology report. An IC section should include options for overall no interval change, significant interval change as described in the report, or no comparable priors.

There are several limitations to this study. First, this was a retrospective study with reports being examined by multiple readers from different hospital settings; furthermore, retrospective categorization of patient location, given the dynamics of care transition at our institution, was impractical. However, all findings were statistically significant. Next, only noncontrast head CTs were included for simplification. It is assumed that similar patterns would be observed in different radiologic subspecialties and modalities. Similarly, comparisons with other modalities such as CTAs and MRIs were not included; however, this feature should not significantly bias the results because they were excluded. Next, the accuracy of every aspect of the reports was not verified. Although highly important, it was considered outside the scope of this study, which focused on how IC of individual findings is used in the report. In addition, we attempted to evaluate IC from both a radiologist's and referring clinician's perspectives. For practical purposes, basic accuracy was assumed. Finally, the definition of an explicitly stated IC in this study may be seen as overly exacting, though similar to definitions used in the literature.³ In addition, given the relative paucity of prior precedent in the scientific literature,³ our finding categorizations were arbitrary. Some of the findings we identified would not be anticipated to have changed in most settings. However, our definitions fulfilled our most important criterion: Would a clinician with no knowledge of the case be able to discern whether there was a prior study. Furthermore, the use of simple phrases like “unchanged” and “otherwise unchanged,” we would argue, is straightforward for clinicians to understand and not overly demanding for radiologists to use.