Table 3. Results of subgroup analysis in diagnostic accuracy of miR-21 for breast cancer.

Subgroup	No. of studies (No. of cases)	Sensitivity (95% CI)	Specificity (95% CI)	PLR (95% CI)	NLR (95% CI)	DOR (95% CI)	AUC
Ethnicity
Asian	7 (675)	0.70 (0.66–0.73)	0.79 (0.76–0.83)	3.27 (1.92–5.56)	0.33 (0.17–0.62)	10.64 (3.66–30.97)	0.8472
Caucasian	4 (243)	0.77 (0.72–0.82)	0.83 (0.74–0.90)	3.65 (2.18–6.11)	0.29 (0.17–0.49)	13.73 (5.54–34.04)	0.8625
Sample size
≥ 100	5 (605)	0.67 (0.63–0.71)	0.76 (0.71–0.80)	2.32 (1.41–3.82)	0.38 (0.19–0.75)	6.31 (2.09–19.00)	0.7935
< 100	6 (313)	0.80 (0.75–0.84)	0.87 (0.82–0.91)	4.89 (3.13–7.62)	0.26 (0.15–0.44)	20.89 (10.14–43.06)	0.8948
Sample types
Serum	8 (588)	0.67 (0.63–0.71)	0.81 (0.77–0.85)	3.95 (2.19–7.12)	0.31 (0.17–0.57)	13.46 (4.37–41.41)	0.8865
Tissue	2 (160)	0.86 (0.79–0.91)	0.60 (0.36–0.81)	2.07 (1.20–3.56)	0.26 (0.11–0.62)	8.04 (2.86–22.58)	—
Plasma	1 (170)	—	—	—	—	—	—
Reference control
miR-16	3 (185)	0.70 (0.63–0.76)	0.90 (0.83–0.95)	6.18 (3.51–10.89)	0.36 (0.24–0.55)	18.81 (9.06–39.06)	0.8954
18S RNA	3 (221)	0.88 (0.83–0.92)	0.67 (0.47–0.83)	2.37 (1.44–3.89)	0.17 (0.06–0.46)	15.09 (3.49–65.19)	0.5981
CA153, CEA	2 (209)	0.82 (0.74–0.89)	0.87 (0.79–0.93)	5.86 (3.59–9.58)	0.23 (0.09–0.63)	15.40 (6.97–92.54)	—
RNA extraction
TRIzol	6 (554)	0.78 (0.75–0.82)	0.84 (0.79–0.88)	4.45 (3.02–6.54)	0.28 (0.19–0.40)	17.90 (10.63–30.15)	0.8800
Others	5 (364)	0.62 (0.56–0.67)	0.77 (0.72–0.81)	2.36 (1.35–4.13)	0.36 (0.17–0.77)	6.84 (1.95–23.97)	0.8058
Measurements
SYBR	5 (384)	0.80 (0.75–0.84)	0.87 (0.81–0.92)	5.02 (3.09–8.16)	0.26 (0.16–0.43)	23.59 (13.66–40.73)	0.8974
Taqman	6 (534)	0.78 (0.73–0.81)	0.77 (0.71–0.82)	3.02 (2.17–4.19)	0.32 (0.22–0.45)	10.03 (5.50–18.26)	0.8289