Table 1. Studies that Directly Compared Low- and Conventional-Dose CTs as First-Line Imaging Test for Diagnosing Appendicitis.

Study	Comparison		Study Type*	Population/Sample			Results
	Low-Dose CT/Contrast Material	Conventional-Dose CT/Contrast Material		Age (Years)	Clinical Presentation†‡	Sample Size§	Outcome	Low-Dose CT vs. Conventional-Dose CT
Keyzer et al. 2004 [36] Radiology	1–2 mSv	5–7 mSv	Retrospectiveǁ	16–74	NS	29/95¶	AUC	0.92–0.93 vs. 0.91–0.93
	None	None	Scan each patient twice				Sensitivity, %	97–100 vs. 97–100
			MRMC (2 readers)				Specificity, %	80–94 vs. 82–94
Keyzer et al. 2009 [37] AJR Am J Roentgenol	30 mAs eff and 120 kVp (simulated**)	100 mAseff and 120 kVp	Retrospectiveǁ	18–87	NS	33/131 ††	With IV contrast
	With or without oral††	With or without oral††	Dose simulation				Sensitivity, %	76–88 vs. 91
			MRMC (2 readers)				Specificity, %	98–99 vs. 97–99
							Without IV contrast
							Sensitivity, %	82–91 vs. 79–82
							Specificity, %	90–95 vs. 95
Seo et al. 2009 [38] AJR Am J Roentgenol	4 mSv	8 mSv	Retrospective	15–83	Typical and atypical	78/207¶	AUC	0.98–0.99 vs. 0.97–0.98
	None	IV	Scan each patient twice				Sensitivity, %	98.7–100 vs. 100
			MRMC (2 readers)				Specificity, %	95.3–96.9 vs. 93–96.9
Platon et al. 2009 [39] Eur Radiol	1–2 mSv	7–10 mSv	Retrospectiveǁ	18–96	NS	37/86¶	Sensitivity, %	95 vs. 100
	Oral	Oral and IV	Scan each patient twice				Specificity, %	96 vs. 96
			MRMC (2 readers)
Kim et al. 2011 [40] Radiology	2 mSv	8 mSv	Retrospective	15–40	Typical and atypical	95/257‡‡	NAR, %	4.5 vs. 1.9
	IV	IV	Prospective image interpretation				APR, %	33 vs. 13
			Before-and-after design				AUC	0.96 vs. 0.97
							Sensitivity, %	90 vs. 89
							Specificity, %	92 vs. 94
Kim et al. 2012 [41] N Engl J Med	2 mSv	8 mSv	Prospective	15–44§§	Typical and atypical	346/891‡‡	NAR, %	3.5 vs. 3.2
	IV	IV	RCT				APR, %	26.5 vs. 23.3
							AUC	0.97 vs. 0.98
							Sensitivity, %	94.5 vs. 95.0
							Specificity, %	93.3 vs. 93.8
Kim et al. 2015 [42] Acta Radiol	2 mSv	4 mSv	Retrospectiveǁ	15–82	NS	58/102¶	AUC	0.96–0.97 vs. 0.93–0.97
	IV (portal phase)	IV (arterial phase)	Scan each patient twice
	IR	FBP	MRMC (2 readers)
LOCAT Group 2017 [43] Lancet Gastroenterol Hepatol	2 mSv	8 mSv	Prospective	15–44§§	Typical and atypical	1088/3074‡‡	NAR, %	3.9 vs. 2.7
	IV	IV	RCT				APR, %	34.7 vs. 31.2
							AUC	0.983 vs. 0.986
							Sensitivity, %	97.1 vs. 98.0
							Specificity, %	95.8 vs. 94.0
Sippola et al. 2020 [60] Ann Surg	3 mSv	4 mSv	Prospective	18–60	NS	49/57¶	Accuracy, %	79 vs. 80
	IV	IV	Scan each patient twice
			MRMC (2 readers)

^*All studies except for that by the LOCAT Group were single-institutional studies, ^†In all studies, clinical presentation was described as suspected appendicitis, ^‡If patients with typical presentation and/or patients with atypical presentation of appendicitis were included, ^§Number of confirmed appendicitis/number of patients undergoing CT, ^∥Patients were included prospectively, but images were reviewed retrospectively, ^¶Each patient underwent low- and then conventional-dose CTs, ^**Low-dose CT was simulated by adding noise to original scans, ^††Patients were randomized into oral-contrast or no-oral-contrast group. Each patient underwent conventional-dose CT before and after IV contrast enhancement, ^‡‡Each patient underwent either low- or conventional-dose, ^§§Inclusion criteria. APR = appendiceal perforation rate, AUC = area under the receiver operating characteristic curve, FBP = filtered back-projection, IR = iterative reconstruction, IV = intravenous, mAseff = effective mAs, MRMC = multireader multicase, NAR = negative appendectomy rate, NS = not specified, RCT = randomized controlled trial