. 2019 Nov 19;2019(11):CD009977. doi: 10.1002/14651858.CD009977.pub2

4. Subgroup analyses according to type of contrast enhancement and radiation dose.

Subgroups by enhancement and dose	Number of analyses (studies)^a	Summary estimates with 95% CI				Absolute differences in summary estimates with 95% CI
Subgroups by enhancement and dose	Number of analyses (studies)^a	Sensitivity	Specificity	Positive likelihood ratio	Negative likelihood ratio	Sensitivity	Specificity
Unenhanced	19 (19)	0.91  (0.87‐0.93)	0.94  (0.90–0.96)	15  (9–24)	0.10  (0.07–0.14)	–	–
IV contrast	18 (17)	0.96 (0.92–0.98)	0.93  (0.90–0.95)	14  (9–20)	0.04  (0.02–0.09)	0.04^b  (0.00–0.09)	‐0.01^b  (‐0.04–0.03)
IV and oral contrast	15 (15)	0.96  (0.93–0.98	0.94  (0.92–0.96)	17  (12–26)	0.04 (0.02–0.07)	0.05^b (0.01–0.09)	0.01^b (‐0.03–0.04)
Rectal contrast	9 (9)	0.97  (0.93–0.99)	0.95  (0.90–0.98)	21  (9–51)	0.04  (0.02–0.08)	0.05^b (0.01–0.09)	0.01^b (‐0.03–0.06)
Oral contrast	7 (7)	0.89 (0.81–0.94)	0.94 (0.90–0.97)	16 (9–29)	0.11 (0.06–0.21)	‐0.01^b (‐0.08–0.6)	0.01^b (‐0.03–0.05)
Standard dose	67 (64)	0.95 (0.93–0.96)	0.94 (0.92–0.95)	15.6  (12.3–19.7)	0.05  (0.04–0.07)	–	–
Low dose	8 (7)	0.94 (0.90–0.97)	0.94 (0.91–0.96)	16 (10–24)	0.06  (0.03–0.11)	0.00^c  (‐0.04–0.05)	0.00^c  (‐0.04–0.03)
Overall	71	0.95  (0.93–0.96)	0.94  (0.92–0.95)	15  (12–19 )	0.05  (0.04–0.07)	‐	‐

CI: confidence interval.  IV: intravenous.  ^aRandomised and paired studies provided two or more analyses.  ^bAbsolute difference compared to unenhanced CT.  ^cAbsolute difference compared to standard‐dose CT.