Synthetic hematocrit derived from the longitudinal relaxation of blood can lead to clinically significant errors in measurement of extracellular volume fraction in pediatric and young adult patients

Table 4 Clinical miscategorization of abnormal ECV in the three models

	Published Model		Static ECV		Local Model
	ECV_mid-septum	ECV_{mid-free wall}	ECV_mid-septum	ECV_{mid-free wall}	ECV_mid-septum	ECV_{mid-free wall}
False Negative	41 (30)	26 (19)	34 (32)	26 (24)	14 (9)	12 (6)
False Positive	4 (8)	3 (2)	3 (3)	1 (2)	12 (11)	8 (6)
Both false negative	14 (9)		12 (12)		6 (2)
Both false positive	1 (0)		1 (0)		3 (3)
Total unique miscategorizations	59 (50)		51 (49)		37 (27)

Using a threshold ECV of 28.5% for abnormal (3 SD), the number of false negatives and false positives were determined for each model
The local model had substantially fewer total miscategorizations, although at the expense of an increased frequency of false positives. Numbers in parentheses are the number of instances in each classification using a threshold of 27.0% (2 SD)

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