Interobserver Agreement in the Interpretation of Outpatient Head CT Scans in an Academic Neuroradiology Practice

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Fig 1.
Class 2 discrepancies in pertinent findings. A, A patient followed for recurrence of a resected breast cancer metastasis; one reader reported a recurrence (arrow), whereas the other observer did not mention this finding. B, A lytic lesion of the clivus (circle) was reported by one but not the other reader.
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Fig 2.
Class 2 discrepancies in incidental findings. A, One reader reported a polypoid posterior nasal lesion (arrow), whereas the other observer did not mention this incidental finding. B, A pineal cyst (circle) was mentioned in only 1 of the 2 reports.

Table 1:

Agreement among double-blind reports

	Concordant Readings (CI 95%)	Class 2 Discrepancies	Class 1 Discrepancies
Clinically pertinent findings	75.6% (n = 90) (67.2%–82.5%)	15.1% (n = 18)	9.2% (n = 11)
Incidental findings	65.5% (n = 78) (56.6%–73.5%)	29.4% (n = 35)	5% (n = 6)
Answer to the clinician's question	86.7% (n = 85) (78%–92.5%)	12.2% (n = 12)	1% (n = 1)
Further investigations	86.6% (n = 103) (79.2%–91.6%)	13.4% (n = 16)

Table 2:

Class 2 discrepancies in clinically significant findings

	Age (yr)	Sex	NC or CE	Context	Discrepancies
1	66	F	CE	F-up meningioma	Progression vs stable
2	82	F	CE	F-up meningioma	Progression vs stable
3	47	M	NC	F-up subdural hematoma	Complete resolution vs partial regression
4	60	F	NC	F-up hydrocephalus	Stable vs progression
5	47	F	CE	F-up metastasis resection	No recurrence vs recurrence suspicion
6	77	M	CE	Lymphoma	Normal vs clival lesion
7	76	M	NC	F-up pituitary apoplexy	Unchanged vs new hemorrhage
8	63	M	NC	F-up glaucoma	Optic nerve atrophy vs normal
9	66	M	NC	F-up subdural hematoma	Persistence vs complete resolution
10	64	F	NC	Post-op adenoma	Residual mass vs normal
11	75	F	CE	Seizures	Schizencephaly vs no mention
12	74	M	NC	F-up subdural hematoma	Rebleeding vs no rebleeding
13	58	F	CE	F-up metastases	No recurrence vs recurrence
14	37	F	NC	F-up glioblastoma	Herniation vs no mention
15	62	F	CE	Breast CA	Choroidal mets suspicion vs no mention
16	77	F	NC	Dementia	White matter disease vs no mention
17	76	M	CE	Memory loss	Cerebral trophy vs no mention
18	42	M	CE	F-up glioblastoma	Progression vs stable